| 1. |
- Bourne, N., et al.
(författare)
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Evolution of cosmic star formation in the SCUBA-2 Cosmology Legacy Survey
- 2017
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 467:2, s. 1360-1385
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Tidskriftsartikel (refereegranskat)abstract
- We present a new exploration of the cosmic star formation history and dust obscuration in massive galaxies at redshifts 0.5 10(10) M-O galaxies at 0.5 10. One third of this is accounted for by 450 mu m-detected sources, while one-fifth is attributed to UV-luminous sources (brighter than L-UV(*)), although even these are largely obscured. By extrapolating our results to include all stellar masses, we estimate a total SFRD that is in good agreement with previous results from IR and UV data at z
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| 2. |
- Casey, Caitlin M., et al.
(författare)
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Physical Characterization of an Unlensed, Dusty Star-forming Galaxy at z = 5.85
- 2019
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 887:1
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Tidskriftsartikel (refereegranskat)abstract
- We present a physical characterization of MM J100026.36+021527.9 (a.k.a. "Mambo-9"), a dusty star-forming galaxy (DSFG) at z = 5.850 ± 0.001. This is the highest-redshift unlensed DSFG (and fourth most distant overall) found to date and is the first source identified in a new 2 mm blank-field map in the COSMOS field. Though identified in prior samples of DSFGs at 850 μm to 1.2 mm with unknown redshift, the detection at 2 mm prompted further follow-up as it indicated a much higher probability that the source was likely to sit at z > 4. Deep observations from the Atacama Large Millimeter and submillimeter Array (ALMA) presented here confirm the redshift through the secure detection of 12CO(J = 6→5) and p-H2O (21,1 → 20,2). Mambo-9 is composed of a pair of galaxies separated by 6 kpc with corresponding star formation rates of 590 M o˙ yr-1 and 220 M o˙ yr-1, total molecular hydrogen gas mass of (1.7 ± 0.4) × 1011 M o˙, dust mass of (1.3 ± 0.3) × 109 M o˙, and stellar mass of (3.2-1.5+1.0) × 109 M o˙. The total halo mass, (3.3 ± 0.8) × 1012 M o˙, is predicted to exceed 1015 M o˙ by z = 0. The system is undergoing a merger-driven starburst that will increase the stellar mass of the system tenfold in τ depl = 40-80 Myr, converting its large molecular gas reservoir (gas fraction of 96-2+1) into stars. Mambo-9 evaded firm spectroscopic identification for a decade, following a pattern that has emerged for some of the highest-redshift DSFGs found. And yet, the systematic identification of unlensed DSFGs like Mambo-9 is key to measuring the global contribution of obscured star formation to the star formation rate density at z ⪆ 4, the formation of the first massive galaxies, and the formation of interstellar dust at early times (≲1 Gyr).
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| 3. |
- Chen, C. C., et al.
(författare)
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A Spatially Resolved Study of Cold Dust, Molecular Gas, H II Regions, and Stars in the z = 2.12 Submillimeter Galaxy ALESS67.1
- 2017
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 846:2
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Tidskriftsartikel (refereegranskat)abstract
- We present detailed studies of a z = 2.12 submillimeter galaxy, ALESS67.1, using sub-arcsecond resolution ALMA, adaptive optics-aided VLT/SINFONI, and Hubble Space Telescope (HST)/CANDELS data to investigate the kinematics and spatial distributions of dust emission (870 ?m continuum), 12CO(J = 3-2), strong optical emission lines, and visible stars. Dynamical modeling of the optical emission lines suggests that ALESS67.1 is not a pure rotating disk but a merger, consistent with the apparent tidal features revealed in the HST imaging. Our sub-arcsecond resolution data set allows us to measure half-light radii for all the tracers, and we find a factor of 4-6 smaller sizes in dust continuum compared to all the other tracers, including 12CO; also, ultraviolet (UV) and H? emission are significantly offset from the dust continuum. The spatial mismatch between the UV continuum and the cold dust and gas reservoir supports the explanation that geometrical effects are responsible for the offset of the dusty galaxy on the IRX-? diagram. Using a dynamical method we derive an , consistent with other submillimeter galaxies (SMGs) that also have resolved CO and dust measurements. Assuming a single value we also derive resolved gas and star formation rate surface densities, and find that the core region of the galaxy ( kpc) follows the trend of mergers on the Schmidt-Kennicutt relationship, whereas the outskirts ( kpc) lie on the locus of normal star-forming galaxies, suggesting different star formation efficiencies within one galaxy. Our results caution against using single size or morphology for different tracers of the star formation activity and gas content of galaxies, and therefore argue the need to use spatially resolved, multi-wavelength observations to interpret the properties of SMGs, and perhaps even for galaxies in general.
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| 4. |
- Coppin, K. E. K., et al.
(författare)
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The SCUBA-2 Cosmology Legacy Survey: the submillimetre properties of Lyman-break galaxies at z=3-5
- 2015
-
Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 446:2, s. 1293-1304
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Tidskriftsartikel (refereegranskat)abstract
- We present detections at 850 mu m of the Lyman-break galaxy (LBG) population at z approximate to 3, 4, and 5 using data from the Submillimetre Common User Bolometer Array 2 Cosmology Legacy Survey in the United Kingdom Infrared Deep Sky Survey 'Ultra Deep Survey' field. We employ stacking to probe beneath the survey limit, measuring the average 850 mu m flux density of LBGs at z approximate to 3, 4, and 5 with typical ultraviolet luminosities of L-1700 approximate to 10(29) erg s(-1) Hz(-1). We measure 850 mu m flux densities of (0.25 +/- 0.03), (0.41 +/- 0.06), and (0.88 +/- 0.23) mJy, respectively, finding that they contribute at most 20 per cent to the cosmic far-infrared (IR) background at 850 mu m. Fitting an appropriate range of spectral energy distributions to the z similar to 3, 4, and 5 LBG stacked 24-850 mu m fluxes, we derive IR luminosities of L8-1000 (mu m) approximate to 3.2, 5.5, and 11.0 x 10(11) L-circle dot [and star formation rates (SFRs) of approximate to 50-200M(circle dot) yr(-1)], respectively. We find that the evolution in the IR luminosity density of LBGs is broadly consistent with model predictions for the expected contribution of luminous-to-ultraluminous IR galaxies at these epochs. We observe a positive correlation between stellar mass and IR luminosity and confirm that, for a fixed mass, the reddest LBGs (UV slope beta -> 0) are redder due to dust extinction, with SFR (IR)/SFR (UV) increasing by about an order of magnitude over -2
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| 5. |
- Fan, Lulu, 1982, et al.
(författare)
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ALMA Detections of CO Emission in the Most Luminous, Heavily Dust-obscured Quasars at z > 3
- 2018
-
Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 856:1
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Tidskriftsartikel (refereegranskat)abstract
- We report the results of a pilot study of CO(4 - 3) emission line of three Wide-field Infrared Survey Explorer (WISE)-selected hyper-luminous, dust-obscured quasars (QSOs) with sensitive ALMA Band 3 observations. These obscured QSOs with L bol > 10 14 L o; are among the most luminous objects in the universe. All three QSO hosts are clearly detected both in continuum and in CO(4 - 3) emission line. Based on CO(4 - 3) emission line detection, we derive the molecular gas masses (∼10 10-11 M o; ), suggesting that these QSOs are gas-rich systems. We find that the obscured QSOs in our sample follow the similar relation as unobscured QSOs at high redshifts. We also find the complex velocity structures of CO(4 - 3) emission line, which provide the possible evidence for a gas-rich merger in W0149+2350 and possible molecular outflow in W0220+0137 and W0410-0913. Massive molecular outflow can blow away the obscured interstellar medium and make obscured QSOs evolve toward the UV/optical bright, unobscured phase. Our result is consistent with the popular active galactic nucleus (AGN) feedback scenario involving the co-evolution between the supermassive black holes and host galaxy.
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| 6. |
- Fan, Lulu, et al.
(författare)
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ALMA Reveals a Gas-rich, Maximum Starburst in the Hyperluminous, Dust-obscured Quasar W0533-3401 at z similar to 2.9
- 2019
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 887:1
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Tidskriftsartikel (refereegranskat)abstract
- We present ALMA observations and multiwavelength spectral energy distribution analysis in a Wide-field Infrared Survey Explorer-selected, hyperluminous dust-obscured quasar W0533-3401 at z = 2.9. We derive the physical properties of each of its components, such as molecular gas, stars, dust, and the central supermassive black hole (SMBH). Both the dust continuum at 3 mm and the CO (3-2) line are detected. The derived molecular gas mass M-gas = 8.4 x 10(10) M-circle dot and its fraction f(gas) = 0.7 suggest that W0533-3401 is gas-rich. The star formation rate (SFR) has been estimated to be similar to 3000-7000M(circle dot) yr(-1) by using different methods. The high values of SFR and specific SFR suggest that W0533-3401 is a maximum starburst. The corresponding gas depletion timescales are very short (t(depl) similar to 12-28 Myr). The CO (3-2) emission line is marginally resolved and has a velocity gradient, which is possibly due to a rotating gas disk, gas outflow, or merger. Finally, we infer the black hole mass growth rate of W0533-3401 ((M)over dot(BH) = 49 M-circle dot yr(-1)), which suggests a rapid growth of the central SMBH. The observed black hole to stellar mass ratio M-BH/M-* of W0533-3401, which is dependent on the adopted Eddington ratio, is over one order of magnitude higher than the local value, and is evolving toward the evolutionary trend of unobscured quasars. Our results are consistent with the scenario that W0533-3401, with both a gas-rich maximum starburst and a rapid black hole growth, is experiencing a short transition phase toward an unobscured quasar.
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| 7. |
- Fan, Lulu, 1982, et al.
(författare)
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Infrared Spectral Energy Distribution Decomposition of Wise-Selected, Hyperluminous Hot Dust-Obscured Galaxies
- 2016
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Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 823:2, s. Art. no. 107-
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Tidskriftsartikel (refereegranskat)abstract
- We utilize a Bayesian approach to fit the observed mid-IR-To-submillimeter/millimeter spectral energy distributions (SEDs) of 22 WISE-selected and submillimeter-detected, hyperluminous hot dust-obscured galaxies (Hot DOGs), with spectroscopic redshift ranging from 1.7 to 4.6. We compare the Bayesian evidence of a torus plusgraybody (Torus+GB) model with that of a torus-only (Torus) model and find that the Torus+GB model has higher Bayesian evidence for all 22 Hot DOGs than the torus-only model, which presents strong evidence in favor of the Torus+GB model. By adopting the Torus+GB model, we decompose the observed IR SEDs of Hot DOGs into torus and cold dust components. The main results are as follows. (1) Hot DOGs in our submillimeter-detected sample are hyperluminous , with torus emission dominating the IR energy output. However, cold dust emission is non-negligible, contributing on average of total IR luminosity. (2) Compared to QSO and starburst SED templates, the median SED of Hot DOGs shows the highest luminosity ratio between mid-IR and submillimeter at rest frame, while it is very similar to that of QSOs at , suggesting that the heating sources of Hot DOGs should be buried AGNs. (3) Hot DOGs have high dust temperatures ( K) and high IR luminosity of cold dust. The relation of Hot DOGs suggests that the increase in IR luminosity for Hot DOGs is mostly due to the increase of the dust temperature, rather than dust mass. Hot DOGs have lower dust masses than submillimeter galaxies (SMGs) and QSOs within a similar redshift range. Both high IR luminosity of cold dust and relatively low dust mass in Hot DOGs can be expected by their relatively high dust temperatures. (4) Hot DOGs have high dust-covering factors (CFs), which deviate from the previously proposed trend of the dust CF decreasing with increasing bolometric luminosity. Finally, we can reproduce the observed properties in Hot DOGs by employing a physical model of galaxy evolution. This result suggests that Hot DOGs may lie at or close to peaks of both star formation and black hole growth histories, and represent a transit phase during the evolutions of massive galaxies, transforming them from the dusty starburst-dominated phase to the optically bright QSO phase.
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| 8. |
- Fan, Lulu, 1982, et al.
(författare)
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Panchromatic modeling of the extremely luminous dust-obscured quasars at the cosmic noon
- 2019
-
Ingår i: Proceedings of the International Astronomical Union. - 1743-9213 .- 1743-9221. ; 15:S341, s. 268-270
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Konferensbidrag (refereegranskat)abstract
- The massive galaxies and their central supermassive black holes (SMBHs) co-evolution scenario proposes that a gas-rich major merger can trigger the central starburst and feeding the SMBH accretion, and then star formation is eventually quenched by quasar feedback. In this evolutionary sequence, dust-obscured quasars may represent the critical transition phase between starburst and unobscured quasars. Modeling the panchromatic emission of these hidden monsters provides a unique way to explore their physical properties and therefore the co-evolution between SMBHs and their hosts. However, most of modelling methods are not suitable for the extremely luminous systems with obscured Active Galactic Nucleus (AGN) emission. Here we present two case studies of panchromatic modeling of the extremely luminous dust-obscured quasars at the cosmic noon.
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| 9. |
- Fan, Lulu, 1982, et al.
(författare)
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The SCUBA-2 850 mu m Follow-up of WISE-selected, Luminous Dust-obscured Quasars
- 2017
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Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 129:982
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Tidskriftsartikel (refereegranskat)abstract
- Hot dust-obscured galaxies (Hot DOGs) are a new population recently discovered in the Wide-field Infrared Survey Explorer All-Sky survey. Multiwavelength follow-up observations suggest that they are luminous, dust-obscured quasars at high redshift. Here we present the JCMT SCUBA-2 850 mu m follow-up observations of 10 Hot DOGs. Four out of ten Hot DOGs have been detected at >3 sigma level. Based on the IR SED decomposition approach, we derive the IR luminosities of AGN torus and cold dust components. Hot DOGs in our sample are extremely luminous with most of them having L-IR(tot) > 10(14) L-circle dot. The torus emissions dominate the total IR energy output. However, the cold dust contribution is still non-negligible, with the fraction of the cold dust contribution to the total IR luminosity (similar to 8%-24%) being dependent on the choice of torus model. The derived cold dust temperatures in Hot DOGs are comparable to those in UV bright quasars with similar IR luminosity, but much higher than those in SMGs. Higher dust temperatures in Hot DOGs may be due to the more intense radiation field caused by intense starburst and obscured AGN activities. Fourteen and five submillimeter serendipitous sources in the 10 SCUBA-2 fields around Hot DOGs have been detected at >3 sigma and >3.5 sigma levels, respectively. By estimating their cumulative number counts, we confirm the previous argument that Hot DOGs lie in dense environments. Our results support the scenario in which Hot DOGs are luminous, dust-obscured quasars lying in dense environments, and being in the transition phase between extreme starburst and UV-bright quasars.
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| 10. |
- Fan, Lulu, 1982, et al.
(författare)
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The Spectral Energy Distribution of the Hyperluminous, Hot Dust-obscured Galaxy W2246-0526
- 2018
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 854:2
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Tidskriftsartikel (refereegranskat)abstract
- Hot dust-obscured galaxies (Hot DOGs) are a luminous, dust-obscured population recently discovered in the WISE All-Sky survey. Multiwavelength follow-up observations suggest that they are mainly powered by accreting supermassive black holes (SMBHs), lying in dense environments, and being in the transition phase between extreme starburst and UV-bright quasars. Therefore, they are good candidates for studying the interplay between SMBHs, star formation, and environment. W2246-0526 (hereafter, W2246), a Hot DOG at z ∼ 4.6, has been taken as the most luminous galaxy known in the universe. Revealed by the multiwavelength images, the previous Herschel SPIRE photometry of W2246 is contaminated by a foreground galaxy (W2246f), resulting in an overestimation of its total IR luminosity by a factor of about two. We perfor m the rest-frame UV/optical-to-far-IR spectral energy distribution (SED) analysis with SED3FIT and re-estimate its physical properties. The derived stellar mass M ∗ = 4.3 × 10 11 M ⊙ makes it among the most massive galaxies with spectroscopic redshift z > 4.5. Its structure is extremely compact and requires an effective mechanism to puff-up. Most of ( > 95%) its IR luminosity is from AGN torus emission, revealing the rapid growth of the central SMBH. We also predict that W2246 may have a significant molecular gas reservoir based on the dust mass estimation.
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| 11. |
- Fogasy, Judit, 1988, et al.
(författare)
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On the frequency of star-forming galaxies in the vicinity of powerful AGNs: The case of SMM J04135+10277
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 597
-
Tidskriftsartikel (refereegranskat)abstract
- Context. In the last decade several massive molecular gas reservoirs were found 108M, and 0.3% have at least one highly star-forming companion (SFR> 100 M yr-1). Conclusions. Our results suggest that quasar-gas-rich companion galaxy systems are common phenomena in the early Universe and the high incidence of companions makes the study of such systems crucial to understand the growth and hierarchical build-up of galaxies and black holes.
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| 12. |
- Geach, J.E., et al.
(författare)
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The SCUBA-2 Cosmology Legacy Survey: 850 μm maps, catalogues and number counts
- 2017
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 465:2, s. 1789-1806
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Tidskriftsartikel (refereegranskat)abstract
- We present a catalogue of similar to 3000 submillimetre sources detected (>= 3.5 sigma) at 850 mu m over similar to 5 deg(2) surveyed as part of the James Clerk Maxwell Telescope (JCMT) SCUBA-2 Cosmology Legacy Survey (S2CLS). This is the largest survey of its kind at 850 mu m, increasing the sample size of 850 mu m selected submillimetre galaxies by an order of magnitude. The wide 850 mu m survey component of S2CLS covers the extragalactic fields: UKIDSS-UDS, COSMOS, Akari-NEP, Extended Groth Strip, Lockman Hole North, SSA22 and GOODS-North. The average 1s depth of S2CLS is 1.2 mJy beam(-1), approaching the SCUBA-2 850 mu m confusion limit, which we determine to be sigma(c) approximate to 0.8 mJy beam(-1). We measure the 850 mu m number counts, reducing the Poisson errors on the differential counts to approximately 4 per cent at S-850 approximate to 3 mJy. With several independent fields, we investigate field-to-field variance, finding that the number counts on 0.5 degrees-1 degrees scales are generally within 50 per cent of the S2CLS mean for S-850 > 3 mJy, with scatter consistent with the Poisson and estimated cosmic variance uncertainties, although there is a marginal (2 sigma) density enhancement in GOODS-North. The observed counts are in reasonable agreement with recent phenomenological and semi-analytic models, although determining the shape of the faint-end slope (S-850 < 3 mJy) remains a key test. The large solid angle of S2CLS allows us to measure the bright-end counts: at S-850 > 10 mJy there are approximately 10 sources per square degree, and we detect the distinctive up-turn in the number counts indicative of the detection of local sources of 850 mu m emission
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| 13. |
- Hashimoto, Takuya, et al.
(författare)
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Big Three Dragons: A z=7.15 Lyman-break galaxy detected in [Oiii] 88 mu m, [Cii] 158 mu m, and dust continuum with ALMA
- 2019
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Ingår i: Publication of the Astronomical Society of Japan. - : Oxford University Press (OUP). - 2053-051X .- 0004-6264. ; 71:4
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Tidskriftsartikel (refereegranskat)abstract
- We present new ALMA observations and physical properties of a Lyman break galaxy at z = 7.15. Our target, B14-65666, has a bright ultra-violet (UV) absolute magnitude, M-UV approximate to -22.4, and has been spectroscopically identified in Ly alpha with a small rest-frame equivalent width of approximate to 4 angstrom. A previous Hubble Space TElescope (HST) image has shown that the target is composed of two spatially separated clumps in the rest-frame UV. With ALMA, we have newly detected spatially resolved [Oiii] 88 mu m, [Cii] 158 mu m, and their underlying dust continuum emission. In the whole system of B14-65666, the [Oiii] and [Cii] lines have consistent redshifts of 7.1520 +/- 0.0003, and the [Oiii] luminosity, (34.4 +/- 4.1)x 10(8)L(circle dot), is about three times higher than the [Cii] luminosity, (11.0 +/- 1.4) x 10(8)L(circle dot). With our two continuum flux densities, the dust temperature is constrained to be T-d approximate to 50-60K under the assumption of a dust emissivity index of beta(d) = 2.0-1.5, leading to a large total infrared luminosity of L-TIR approximate to 1 x 10(12)L(circle dot). Owing to our high spatial resolution data, we show that the [Oiii] and [Cii] emission can be spatially decomposed into two clumps associated with the two rest-frame UV clumps whose spectra are kinematically separated by approximate to 200kms(-1). We also find these two clumps have comparable UV, infrared, [Oiii], and [Cii] luminosities. Based on these results, we argue that B14-65666 is a starburst galaxy induced by a major merger. The merger interpretation is also supported by the large specific star formation rate (defined as the star formation rate per unit stellar mass), sSFR Gyr(-1), inferred from our SED fitting. Probably, a strong UV radiation field caused by intense star formation contributes to its high dust temperature and the [Oiii]-to-[Cii] luminosity ratio.
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| 14. |
- Hodge, J. A., et al.
(författare)
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ALMA Reveals Potential Evidence for Spiral Arms, Bars, and Rings in High-redshift Submillimeter Galaxies
- 2019
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 876:2
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Tidskriftsartikel (refereegranskat)abstract
- We present subkiloparsec-scale mapping of the 870 mu m ALMA continuum emission in six luminous (LIR similar to 5 x 10(12 )L(circle dot)) submillimeter galaxies (SMGs) from the ALESS survey of the Extended Chandra Deep Field South. Our high-fidelity 0 ''.07-resolution imaging (similar to 500 pc) reveals robust evidence for structures with deconvolved sizes of less than or similar to 0.5-1 kpc embedded within (dominant) exponential dust disks. The large-scale morphologies of the structures within some of the galaxies show clear curvature and/or clump-like structures bracketing elongated nuclear emission, suggestive of bars, star-forming rings, and spiral arms. In this interpretation, the ratio of the "ring" and "bar" radii (1.9 +/- 0.3) agrees with that measured for such features in local galaxies. These potential spiral/ring/bar structures would be consistent with the idea of tidal disturbances, with their detailed properties implying flat inner rotation curves and Toomre-unstable disks (Q < 1). The inferred one-dimensional velocity dispersions (sigma(r) less than or similar to 70-160 km s(-1)) are marginally consistent with the limits implied if the sizes of the largest structures are comparable to the Jeans length. We create maps of the star formation rate density (Sigma(SFR)) on similar to 500 pc scales and show that the SMGs are able to sustain a given (galaxy-averaged) E-SFR over much larger physical scales than local (ultra)luminous infrared galaxies. However, on 500 pc scales, they do not exceed the Eddington limit set by radiation pressure on dust. If confirmed by kinematics, the potential presence of nonaxisymmetric structures would provide a means for net angular momentum loss and efficient star formation, helping to explain the very high star formation rates measured in SMGs.
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| 15. |
- Hodge, J. A., et al.
(författare)
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Kiloparsec-Scale Dust Disks in High-Redshift Luminous Submillimeter Galaxies
- 2016
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 833:1
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Tidskriftsartikel (refereegranskat)abstract
- We present high-resolution (0 ''.6) 870 mu m Atacama Large Millimeter/submillimeter Array (ALMA) imaging of 16 luminous (LIR similar to 4 x 10(12) L-circle dot) submillimeter galaxies (SMGs) from the ALESS survey of the Extended Chandra Deep Field South. This dust imaging traces the dust-obscured star formation in these z similar to 2.5 galaxies on similar to 1.3 kpc scales. The emission has a median effective radius of R-e = 0 ''.24 +/- 0 ''.02, corresponding to a typical physical size of R-e= 1.8 +/- 0.2 kpc. We derive a median Sersic index of n = 0.9 +/- 0.2, implying that the dust emission is remarkably disk-like at the current resolution and sensitivity. We use different weighting schemes with the visibilities to search for clumps on 0 ''.12. (similar to 1.0 kpc) scales, but we find no significant evidence for clumping in the majority of cases. Indeed, we demonstrate using simulations that the observed morphologies are generally consistent with smooth exponential disks, suggesting that caution should be exercised when identifying candidate clumps in even moderate signal-to-noise ratio interferometric data. We compare our maps to comparable-resolution Hubble Space Telescope H-160-band images, finding that the stellar morphologies appear significantly more extended and disturbed, and suggesting that major mergers may be responsible for driving the formation of the compact dust disks we observe. The stark contrast between the obscured and unobscured morphologies may also have implications for SED fitting routines that assume the dust is co-located with the optical/near-IR continuum emission. Finally, we discuss the potential of the current bursts of star formation to transform the observed galaxy sizes and light profiles, showing that the z similar to 0 descendants of these SMGs are expected to have stellar masses, effective radii, and gas surface densities consistent with the most compact massive (M* similar to 1-2 x 10(11) M-circle dot) early-type galaxies observed locally.
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| 16. |
- Knudsen, Kirsten Kraiberg, 1976, et al.
(författare)
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A merger in the dusty, z=7.5 galaxy A1689-zD1?
- 2017
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 466:1, s. 138-146
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Tidskriftsartikel (refereegranskat)abstract
- The gravitationally lensed galaxy A1689-zD1 is one of the most distant spectroscopically confirmed sources (z = 7.5). It is the earliest known galaxy where the interstellar medium (ISM) has been detected; dust emission was detected with the Atacama Large Millimetre Array (ALMA). A1689-zD1 is also unusual among high-redshift dust emitters as it is a sub-L* galaxy and is therefore a good prospect for the detection of gaseous ISM in a more typical galaxy at this redshift. We observed A1689-zD1 with ALMA in bands 6 and 7 and with the Green Bank Telescope (GBT) in band Q. To study the structure of A1689-zD1, we map the mm-thermal dust emission and find two spatial components with sizes about 0.4 - 1.7 kpc (lensing-corrected). The rough spatial morphology is similar to what is observed in the near-infrared with HST and points to a perturbed dynamical state, perhaps indicative of a major merger or a disc in early formation. The ALMA photometry is used to constrain the far-infrared spectral energy distribution, yielding a dust temperature (T-dust similar to 35-45 K for beta = 1.5 - 2). We do not detect the CO(3-2) line in the GBT data with a 95 per cent upper limit of 0.3 mJy observed. We find a slight excess emission in ALMA band 6 at 220.9 GHz. If this excess is real, it is likely due to emission from the [C Pi] 158.8 mu m line at z([C II]) = 7.603. The stringent upper limits on the [C coproduct] L-FIR luminosity ratio suggest a [C coproduct] deficit similar to several bright quasars and massive starbursts.
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| 17. |
- Knudsen, Kirsten Kraiberg, 1976, et al.
(författare)
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C II emission in z similar to 6 strongly lensed, star-forming galaxies
- 2016
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966 .- 1745-3925 .- 1745-3933. ; 462:1, s. L6-L10
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Tidskriftsartikel (refereegranskat)abstract
- The far-infrared fine-structure line [C II] at 1900.5 GHz is known to be one of the brightest cooling lines in local galaxies, and therefore it has been suggested to be an efficient tracer for star formation in very high redshift galaxies. However, recent results for galaxies at z > 6 have yielded numerous non-detections in star-forming galaxies, except for quasars and submillimetre galaxies. We report the results of ALMA observations of two lensed, star-forming galaxies at z = 6.029 and z = 6.703. The galaxy A383-5.1 (star formation rate [SFR] of 3.2 M-circle dot yr(-1) and magnification of mu = 11.4 +/- 1.9) shows a line detection with L-[C II] = 8.9 x 10(6) L-circle dot, making it the lowest L-[C II] detection at z > 6. For MS0451-H (SFR = 0.4 M-circle dot yr(-1) and mu = 100 +/- 20) we provide an upper limit of L-[C II] 6; however, other effects could also play a role in terms of decreasing L-[CII]. The detection of A383-5.1 is encouraging and suggests that detections are possible, but much fainter than initially predicted.
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| 18. |
- Knudsen, Kirsten Kraiberg, 1976, et al.
(författare)
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Stacking of Interferometric Data: New Tools for Stacking of ALMA Data
- 2015
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Ingår i: 4th ALMA Science Conference on Revolution in Astronomy with ALMA: The Third Year, Tokyo, Japan, 8-11 December. - 9781583818831 ; 499, s. 81-82
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Radio and mm observations play an important role in determining the star formation properties of high-redshift galaxies. With the unprecedented sensitivity, ALMA now enable studies of faint, distant star-forming galaxies. However, most galaxies with low star formation rates at high redshift are too faint to be detected individually at these wavelengths. A way to study such galaxies is to use stacking. By averaging the emission of a large number of galaxies detected in optical or near-infrared surveys, we can achieve statistical detection. We investigate methods for stacking data from interferometric surveys. Interferometry poses unique challenges in stacking due to the nature of this data. We have compared stacking of uv-data with stacking of imaged data, the latter being the commonly used approach. Using simulated data, we find that uv-stacking may provide up to 50% less noise and that image based stacking systematically loses around 10% of the flux. More importantly, we find that the uv-stacking yield more robust results, especially in the case of (marginally) resolved sources and mosaicked data.
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| 19. |
- Knudsen, Kirsten Kraiberg, 1976, et al.
(författare)
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Stacking of SKA data: comparing uv-plane and and image-plane stacking
- 2015
-
Ingår i: Proceedings of Science. - Trieste, Italy : Sissa Medialab. - 1824-8039. ; 9-13-June-2014
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Konferensbidrag (refereegranskat)abstract
- Stacking as a tool for studying objects that are not individually detected is becoming popular even for radio interferometric data, and will be widely used in the SKA era. Stacking is typically done using imaged data rather than directly using the visibilities (the uv-data). We have investigated and developed a novel algorithm to do stacking using the uv-data. We have performed exten- sive simulations comparing to image-stacking, and summarize the results of these simulations. Furthermore, we disuss the implications in light of the vast data volume produced by the SKA. Having access to the uv-stacked data provides a great advantage, as it allows the possibility to properly analyse the result with respect to calibration artifacts as well as source properties such as size. For SKA the main challenge lies in archiving the uv-data. For purposes of robust stacking analysis, it would be strongly desirable to either keep the calibrated uv-data at least in an aver- age form, or implement a stacking queue where stacking positions could be provided prior to the observations and the uv-stacking is done almost in real time.
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| 20. |
- Koprowski, M. P., et al.
(författare)
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A direct calibration of thtae IRX-β relation in Lyman-break Galaxies at z = 3-5
- 2018
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 479:4, s. 4355-4366
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Tidskriftsartikel (refereegranskat)abstract
- We use a sample of 4209 Lyman-break galaxies (LBGs) at z ≃ 3, 4, and 5 in the UKIRT Infrared Deep Sky Survey Ultra Deep Survey field to investigate the relationship between the observed slope of the stellar continuum emission in the ultraviolet, β, and the thermal dust emission, as quantified via the so-called 'infrared excess' (IRX=LIR/LUV). Through a stacking analysis, we directly measure the 850-μm flux density of LBGs in our deep (0.9 mJy) James Clerk Maxwell Telescope SCUBA-2 850-μm map as well as deep public Herschel/SPIRE 250-, 350-, and 500-μm imaging. We establish functional forms for the IRX-β relation to z ~ 5, confirming that there is no significant redshift evolution of the relation, and that the resulting average IRX-β curve is consistent with a Calzetti-like attenuation law. Comparing our results with recent works in the literature, we confirm that discrepancies in the slope of the IRX-β relation are driven by biases in the methodology used to determine the ultraviolet slopes. Consistent results are found when IRX-β is evaluated by stacking in bins of stellar mass, and we argue that the near-linear IRX-M* relationship is a better proxy for correcting observed ultraviolet luminosities to total star formation rates, provided an accurate handle on M* and also gives clues as to the physical driver of the role of dust-obscured star formation in high-redshift galaxies.
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| 21. |
- Koprowski, M. P., et al.
(författare)
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A resolved map of the infrared excess in a Lyman Break Galaxy at z= 3
- 2016
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 828:2
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Tidskriftsartikel (refereegranskat)abstract
- We have observed the dust continuum of 10 z = 3.1 Lyman break galaxies with the Atacama Large Millimeter/submillimeter Array at similar to 450 mas resolution in Band 7. We detect and resolve the 870 mu m emission in one of the targets with a flux density of S-870 = 192 +/- 57 mu Jy, and measure a stacked 3 sigma signal of S-870 = 67 +/- 23 mu Jy for the remaining nine. The total infrared luminosities are L8-1000 = (8.4 +/- 2.3) x 10(10) L-circle dot for the detection and L8-1000 = (2.9 +/- 0.9) x 10(10) L-circle dot for the stack. With Hubble Space Telescope Advanced Camera for Surveys I-band imaging we map the rest-frame UV emission on the same scale as the dust, effectively resolving the "infrared excess" (IRX = L-FIR/L-UV) in a normal galaxy at z = 3. Integrated over the galaxy we measure IRX = 0.56 +/- 0.15, and the galaxy-averaged UV slope is beta = -1.25 +/- 0.03. This puts the galaxy a factor of similar to 10 below the IRX-beta relation for local starburst nuclei of Meurer et al. However, IRX varies by more than a factor of 3 across the galaxy, and we conclude that the complex relative morphology of the dust relative to UV emission is largely responsible for the scatter in the IRX-beta relation at high-z. A naive application of a Meurer-like dust correction based on the UV slope would dramatically overestimate the total star formation rate, and our results support growing evidence that when integrated over the galaxy, the typical conditions in high-z star-forming galaxies are not analogous to those in the local starburst nuclei used to establish the Meurer relation.
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| 22. |
- Lindroos, Lukas, 1986, et al.
(författare)
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Estimating sizes of faint, distant galaxies in the submillimetre regime
- 2016
-
Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 462:2, s. 1192-1202
-
Tidskriftsartikel (refereegranskat)abstract
- We measure the sizes of redshift similar to 2 star-forming galaxies by stacking data from the At-acama Large Millimeter/submillimeter Array (ALMA). We use a uv-stacking algorithm in combination with model fitting in the uv-domain and show that this allows for robust measures of the sizes of marginally resolved sources. The analysis is primarily based on the 344 GHz ALMA continuum observations centred on 88 submillimetre galaxies in the LABOCA ECDFS Submillimeter Survey (ALESS). We study several samples of galaxies at z approximate to 2 with M-* approximate to 5 x 10(10) M-circle dot, selected using near-infrared photometry (distant red galaxies, extremely red objects, sBzK-galaxies, and galaxies selected on photometric redshift). We find that the typical sizes of these galaxies are similar to 0.6 arcsec which corresponds to similar to 5 kpc at z = 2, this agrees well with the median sizes measured in the near-infrared z band (similar to 0.6 arcsec). We find errors on our size estimates of similar to 0.1-0.2 arcsec, which agree well with the expected errors for model fitting at the given signal-to-noise ratio. With the uv-coverage of our observations (18-160 m), the size and flux density measurements are sensitive to scales out to 2 arcsec. We compare this to a simulated ALMA Cycle 3 data set with intermediate length baseline coverage, and we find that, using only these baselines, the measured stacked flux density would be an order of magnitude fainter. This highlights the importance of short baselines to recover the full flux density of high-redshift galaxies.
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| 23. |
- Lindroos, Lukas, 1986, et al.
(författare)
-
Measuring size evolution of distant, faint galaxies in the radio regime
- 2018
-
Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 476:3, s. 3544-3554
-
Tidskriftsartikel (refereegranskat)abstract
- We measure the evolution of sizes for star-forming galaxies as seen in 1.4 GHz continuum radio for z = 0-3. The measurements are based on combined VLA+MERLIN data of the Hubble Deep Field, and using a uv-stacking algorithm combined with model fitting to estimate the average sizes of galaxies. A sample of similar to 1000 star-forming galaxies is selected from optical and near-infrared catalogues, with stellar masses Me-circle dot approximate to 10(10)-10(11) M-circle dot and photometric redshifts 0-3. The median sizes are parametrized for stellar mass M-* = 5 x 10(10) M-circle dot as R-e = A x (H(z)/H(1.5))(alpha z). We find that the median radio sizes evolve towards larger sizes at later times with alpha(z) = 1.1 +/- 0.6, and A (the median size at z approximate to 1.5) is found to be 0 ''.26 +/- 0 ''.07 or 2.3 +/- 0.6 kpc. The measured radio sizes are typically a factor of 2 smaller than those measure in the optical, and are also smaller than the typical H alpha sizes in the literature. This indicates that star formation, as traced by the radio continuum, is typically concentrated towards the centre of galaxies, for the sampled redshift range. Furthermore, the discrepancy of measured sizes from different tracers of star formation, indicates the need for models of size evolution to adopt a multiwavelength approach in the measurement of the sizes star-forming regions.
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| 24. |
- Lindroos, Lukas, 1986, et al.
(författare)
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Stacking of large interferometric data sets in the image- and uv-domain - a comparative study
- 2015
-
Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 446:4, s. 3502-3515
-
Tidskriftsartikel (refereegranskat)abstract
- We present a new algorithm for stacking radio interferometric data in the uv-domain. The performance of uv-stacking is compared to the stacking of fully imaged data using simulated Atacama Large Millimeter/submillimeter Array and the Karl G. Jansky Very Large Array (VLA) deep extragalactic surveys. We find that image-and uv-stacking produce similar results, however, uv-stacking is typically the more robust method. An advantage of the uv-stacking algorithm is the availability of uv-data post-stacking, which makes it possible to identify and remove problematic baselines. For deep VLA surveys uv-stacking yields a signal-to-noise ratio that is up to 20 per cent higher than image-stacking. Furthermore, we have investigated stacking of resolved sources with a simulated VLA data set where 1.5 arcsec (10-12 kpc at z similar to 1-4) sources are stacked. We find that uv-stacking, where a model is fitted directly to the visibilities, significantly improves the accuracy and robustness of the size estimates. While scientific motivation for this work is studying faint, high-z galaxies, the algorithm analysed here would also be applicable in other fields of astronomy. Stacking of radio interferometric data is also expected to play a big role for future surveys with telescopes such as Low-Frequency Array and Square Kilometre Array.
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| 25. |
- Primas, F., et al.
(författare)
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Shaping ESO2020+ Together: Feedback from the Community Poll
- 2015
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Ingår i: The Messenger. - 0722-6691. ; 161, s. 6-14
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A thorough evaluation and prioritisation of the ESO science programme into the 2020+ timeframe took place under the auspices of a working group, comprising astronomers drawn from ESO’s advisory structure and from within ESO. This group reported to ESO’s Scientific Technical Committee, and to ESO Council, concluding the exercise with the publication of a report, “Science Priorities at ESO”. A community poll and a dedicated workshop, held in January 2015, formed part of the information gathering process. The community poll was designed to probe the demographics of the user community, its scientific interests, use of observing facilities and plans for use of future telescopes and instruments, its views on types of observing programmes and on the provision of data processing and archiving. A total of 1775 full responses to the poll were received and an analysis of the results is presented here. Foremost is the importance of regular observing programmes on all ESO observing facilities, in addition to Large Programmes and Public Surveys. There was also a strong community requirement for ESO to process and archive data obtained at ESO facilities. Other aspects, especially those related to future facilities, are more challenging to interpret because of biases related to the distribution of science expertise and favoured wavelength regime amongst the targeted audience. The results of the poll formed a fundamental component of the report and pro-vide useful data to guide the evolution of ESO’s science programme.
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| 26. |
- Rivera, Gabriela Calistro, et al.
(författare)
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Resolving the ISM at the Peak of Cosmic Star Formation with ALMA: The Distribution of CO and Dust Continuum in z ∼2.5 Submillimeter Galaxies
- 2018
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 863:1
-
Tidskriftsartikel (refereegranskat)abstract
- We use Atacama Large Millimeter Array (ALMA) observations of four submillimeter galaxies (SMGs) at z ∼2-3 to investigate the spatially resolved properties of the interstellar medium (ISM) at scales of 1-5 kpc (0.″1-0.″6). The velocity fields of our sources, traced by the12CO(J =3-2) emission, are consistent with disk rotation to the first order, implying average dynamical masses of ∼3 1011within two half-light radii. Through a Bayesian approach we investigate the uncertainties inherent to dynamically constraining total gas masses. We explore the covariance between the stellar mass-to-light ratio and CO-to-H2conversion factor, αCO, finding values of for dark matter fractions of 15%. We show that the resolved spatial distribution of the gas and dust continuum can be uncorrelated to the stellar emission, challenging energy balance assumptions in global SED fitting. Through a stacking analysis of the resolved radial profiles of the CO(3-2), stellar, and dust continuum emission in SMG samples, we find that the cool molecular gas emission in these sources (radii ∼5-14 kpc) is clearly more extended than the rest-frame ∼250 μm dust continuum by a factor >2. We propose that assuming a constant dust-to-gas ratio, this apparent difference in sizes can be explained by temperature and optical depth gradients alone. Our results suggest that caution must be exercised when extrapolating morphological properties of dust continuum observations to conclusions about the molecular gas phase of the interstellar medium (ISM).
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| 27. |
- Sharon, C. E., et al.
(författare)
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A Total Molecular Gas Mass Census in z~ 2-3 Star-forming Galaxies: Low-J CO Excitation Probes of Galaxies' Evolutionary States
- 2016
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 827:1
-
Tidskriftsartikel (refereegranskat)abstract
- We present CO(1-0) observations obtained at the Karl G. Jansky Very Large Array for 14 z similar to 2 galaxies with existing CO(3-2) measurements, including 11 galaxies that. contain active galactic nuclei (AGNs) and three submillimeter galaxies (SMGs). We combine this sample with an additional 15 z similar to 2 galaxies from the literature that have both CO(1-0) and CO(3-2) measurements in order to evaluate differences in CO excitation between SMGs and AGN host galaxies, to. measure the effects of CO excitation on the derived molecular gas properties of these populations, and to look for correlations between the molecular gas excitation and other physical parameters. With our expanded sample of CO(3-2)/CO(1-0) line ratio measurements, we do not find a statistically significant difference in the mean line ratio between SMGs and AGN host galaxies as can be found in the literature; we instead find r(3,1) = 1.03. 0.50 for AGN host galaxies and r(3,1) = 0.78. 0.27 for SMGs (or r(3,1) = 0.90 +/- 0.40 for both populations combined). We also do not measure a statistically significant difference between the distributions of the line ratios for these populations at the p = 0.05 level, although this result is less robust. We find no excitation dependence on the index or offset of the integrated Schmidt-Kennicutt relation for the two CO lines, and we. obtain indices consistent with N = 1 for the various subpopulations. However, including low-z "normal" galaxies increases our best-fit Schmidt-Kennicutt index to N similar to 1.2. While we do not reproduce correlations between the CO line width and luminosity, we do reproduce correlations between CO excitation and star-formation efficiency.
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| 28. |
- Simpson, J. M., et al.
(författare)
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THE SCUBA-2 COSMOLOGY LEGACY SURVEY: ALMA RESOLVES the BRIGHT-END of the SUB-MILLIMETER NUMBER COUNTS
- 2015
-
Ingår i: Astrophysical Journal. - 1538-4357 .- 0004-637X. ; 807:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present high-resolution 870 μm Atacama Large Millimeter/sub-millimeter Array (ALMA) continuum maps of 30 bright sub-millimeter sources in the UKIDSS UDS field. These sources are selected from deep, 1 degree2 850 μm maps from the SCUBA-2 Cosmology Legacy Survey, and are representative of the brightest sources in the field (median SSCUBA-2= 8.7 ± 0.4 mJy). We detect 52 sub-millimeter galaxies (SMGs) at >4σ significance in our 30 ALMA maps. In 61-15+19% of the ALMA maps the single-dish source comprises a blend of ≥2 SMGs, where the secondary SMGs are Ultra-luminous Infrared Galaxies (ULIRGs) with LIR ≳ 1012 L⊙. The brightest SMG contributes on average 80-2+6% of the single-dish flux density, and in the ALMA maps containing ≥2 SMGs the secondary SMG contributes 25-5+1% of the integrated ALMA flux. We construct source counts and show that multiplicity boosts the apparent single-dish cumulative counts by 20% at S870 > 7.5 mJy, and by 60% at S870 > 12 mJy. We combine our sample with previous ALMA studies of fainter SMGs and show that the counts are well-described by a double power law with a break at 8.5 ± 0.6 mJy. The break corresponds to a luminosity of ∼6 × 1012 L⊙ or a star formation rate (SFR) of ∼103 M⊙ yr-1. For the typical sizes of these SMGs, which are resolved in our ALMA data with Re = 1.2 ± 0.1 kpc, this yields a limiting SFR density of ∼100 M⊙ yr-1 kpc-2 Finally, the number density of S870 ≳ 2 mJy SMGs is 80 ± 30 times higher than that derived from blank-field counts. An over-abundance of faint SMGs is inconsistent with line-of-sight projections dominating multiplicity in the brightest SMGs, and indicates that a significant proportion of these high-redshift ULIRGs are likely to be physically associated.
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| 29. |
- Stanley, Flora, 1990, et al.
(författare)
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A spectral stacking analysis to search for faint outflow signatures in z ∼6 quasars
- 2019
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 631
-
Tidskriftsartikel (refereegranskat)abstract
- Aims. Outflows in quasars during the early epochs of galaxy evolution are an important part of the feedback mechanisms that potentially affect the evolution of the host galaxy. However, systematic millimetre (mm) observations of outflows are only now becoming possible with the advent of sensitive mm telescopes. In this study we used spectral stacking methods to search for a faint high-velocity outflow signal in a sample of [C II] detected, z ∼ 6 quasars. Methods. We searched for broad emission line signatures from high-velocity outflows for a sample of 26 ∼ 6 quasars observed with the Atacama Large Millimeter Array (ALMA), with a detection of the [C II] line. The observed emission lines of the sources are dominated by the host galaxy, and outflow emission is not detected for the individual sources. We used a spectral line stacking analysis developed for interferometric data to search for outflow emission. We stacked both extracted spectra and the full spectral cubes. We also investigated the possibility that only a sub-set of our sample contributes to the stacked outflow emission. Results. We find only a tentative detection of a broad emission line component in the stacked spectra. When taking a region of about 2″ around the central position of the stacked cubes, the stacked line shows an excess emission due to a broad component of 1.1-1.5σ, but the significance drops to 0.4-0.7σ when stacking the extracted spectra from a smaller region. The broad component can be characterised by a line width of full width at half-maximum FWHM > 700 km s-1. Furthermore, we find a sub-sample of 12 sources, the stack of which maximises the broad component emission. The stack of this sub-sample shows an excess emission due to a broad component of 1.2-2.5σ. The stacked line of these sources has a broad component of FWHM > 775 km s-1. Conclusions. We find evidence suggesting the presence of outflows in a sub-sample of 12 out of 26 sources, which demonstrates the importance of spectral stacking techniques in tracing faint signal in galaxy samples. However, deeper ALMA observations are necessary to confirm the presence of a broad component in the individual spectra.
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| 30. |
- Stanley, Flora, 1990, et al.
(författare)
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Deep ALMA photometry of distant X-ray AGN: improvements in star formation rate constraints, and AGN identification
- 2018
-
Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 478:3, s. 3721-3739
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Tidskriftsartikel (refereegranskat)abstract
- We present the star formation rates (SFRs) of a sample of 109 galaxies with X-ray selected active galactic nuclei (AGN) with moderate to high X-ray luminosities (L(2-8keV) = 10^42 - 10^45 erg/s), at redshifts 1 < z <4.7, that were selected to be faint or undetected in the Herschel bands. We combine our deep ALMA continuum observations with deblended 8-500um photometry from Spitzer and Herschel , and use infrared (IR) SED fitting and AGN - star formation decomposition methods. The addition of the ALMA photometry results in an order of magnitude more X-ray AGN in our sample with a measured SFR (now 37%). The remaining 63% of the sources have SFR upper limits that are typically a factor of ~2-10 times lower than the pre-ALMA constraints. With the improved constraints on the IR SEDs, we can now identify a mid-IR (MIR) AGN component in 50% of our sample, compared to only ~1% previously. We further explore the F(870um)/F(24um)--redshift plane as a tool for the identification of MIR emitting AGN, for three different samples representing AGN dominated, star formation dominated, and composite sources. We demonstrate that the F(870um)/F(24um)--redshift plane can successfully split between AGN and star formation dominated sources, and can be used as an AGN identification method.
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| 31. |
- Stanley, Flora, 1990, et al.
(författare)
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The mean star formation rates of unobscured QSOs: searching for evidence of suppressed or enhanced star formation
- 2017
-
Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 472:2, s. 2221-2240
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the mean star formation rates (SFRs) in the host galaxies of similar to 3000 optically selected quasi-stellar objects (QSOs) from the Sloan Digital Sky Survey within the Herschel-ATLAS fields, and a radio-luminous subsample covering the redshift range of z = 0.2-2.5. Using Wide-field Infrared Survey Explorer (WISE) and Herschel photometry (12-500 mu m) we construct composite spectral energy distributions (SEDs) in bins of redshift and active galactic nucleus (AGN) luminosity. We perform SED fitting to measure the mean infrared luminosity due to star formation, removing the contamination from AGN emission. We find that the mean SFRs show a weak positive trend with increasing AGN luminosity. However, we demonstrate that the observed trend could be due to an increase in black hole (BH) mass (and a consequent increase of inferred stellar mass) with increasing AGN luminosity. We compare to a sample of X-ray selected AGN and find that the two populations have consistent mean SFRs when matched in AGN luminosity and redshift. On the basis of the available virial BH masses, and the evolving BH mass to stellar mass relationship, we find that the mean SFRs of our QSO sample are consistent with those of main sequence star-forming galaxies. Similarly the radio-luminous QSOs have mean SFRs that are consistent with both the overall QSO sample and with star-forming galaxies on the main sequence. In conclusion, on average QSOs reside on the main sequence of star-forming galaxies, and the observed positive trend between the mean SFRs and AGN luminosity can be attributed to BH mass and redshift dependencies.
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| 32. |
- Wardlow, J. L., et al.
(författare)
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An ALMA survey of CO in submillimetre galaxies: Companions, triggering, and the environment in blended sources
- 2018
-
Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 479:3, s. 3879-3891
-
Tidskriftsartikel (refereegranskat)abstract
- We present ALMA observations of the mid-J 12CO emission from six single-dish selected 870-μm sources in the Extended Chandra Deep Field-South and UKIDSS Ultra-Deep Survey fields. These six single-dish submillimetre sources were selected based on previous ALMA continuum observations, which showed that each comprised a blend of emission from two or more individual submillimetre galaxies (SMGs), separated on 5-10 arcsec scales. The six single-dish submillimetre sources targeted correspond to a total of 14 individual SMGs, of which seven have previously measured robust optical/near-infrared spectroscopic redshifts, which were used to tune our ALMA observations.We detect CO(3-2) or CO(4-3) at z = 2.3- 3.7 in 7 of the 14 SMGs, and in addition serendipitously detect line emission from three gas-rich companion galaxies, as well as identify four new 3.3 mm selected continuum sources in the six fields. Joint analysis of ourCOspectroscopy and existing data suggests that 64(±18) per cent of the SMGs in blended submillimetre sources are unlikely to be physically associated. However, three of the SMG fields (50 per cent) contain new, serendipitously detected CO-emitting (but submillimetre-faint) sources at similar redshifts to the 870 μm selected SMGs we targeted. These data suggest that the SMGs inhabit overdense regions, but that these are not sufficiently overdense on ∼100 kpc scales to influence the source blending given the short lifetimes of SMGs. We find that 21 ± 12 per cent of SMGs have spatially distinct and kinematically close companion galaxies (∼8-150 kpc and ≲ 300 km s-1), which may have enhanced their star formation via gravitational interactions.
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| 33. |
- Watson, D., et al.
(författare)
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A dusty, normal galaxy in the epoch of reionization
- 2015
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 519:7543, s. 327-330
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Tidskriftsartikel (refereegranskat)abstract
- Candidates for the modest galaxies that formed most of the stars in the early Universe, at redshifts z> 7, have been found in large numbers with extremely deep restframe-ultraviolet imaging. But it has proved difficult for existing spectrographs to characterize them using their ultraviolet light. The detailed properties of these galaxies could be measured from dust and cool gas emission at far-infrared wavelengths if the galaxies have become sufficiently enriched in dust and metals. So far, however, the most distant galaxy discovered via its ultraviolet emission and subsequently detected in dust emission is only at z = 3.2, and recent results have cast doubt on whether dust and molecules can be found in typical galaxies at z >= 7. Here we report thermal dust emission from an archetypal early Universe star-forming galaxy, A1689-zDI. We detect its stellar continuum in spectroscopy and determine its redshift to be z = 7.5 +/- 0.2 from a spectroscopic detection of the Lyman-a break. A1689-zD1 is representative of the star-forming population during the epoch of reionization, with a total star-formation rate of about 12 solar masses per year. The galaxy is highly evolved: it has a large stellar mass and is heavily enriched in dust, with a dust-to-gas ratio close to that of the Milky Way. Dusty, evolved galaxies are thus present among the fainter star-forming population at z> 7.
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