| 1. |
- Spinoglio, L., et al.
(författare)
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- 2017
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Ingår i: Publications Astronomical Society of Australia. - : Cambridge University Press (CUP). - 1323-3580 .- 1448-6083. ; 34
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Tidskriftsartikel (refereegranskat)abstract
- IR spectroscopy in the range 12-230 mu m with the SPace IR telescope for Cosmology and Astrophysics (SPICA) will reveal the physical processes governing the formation and evolution of galaxies and black holes through cosmic time, bridging the gap between the James Webb Space Telescope and the upcoming Extremely Large Telescopes at shorter wavelengths and the Atacama Large Millimeter Array at longer wavelengths. The SPICA, with its 2.5-m telescope actively cooled to below 8 K, will obtain the first spectroscopic determination, in the mid-IR rest-frame, of both the star-formation rate and black hole accretion rate histories of galaxies, reaching lookback times of 12 Gyr, for large statistically significant samples. Densities, temperatures, radiation fields, and gas-phase metallicities will be measured in dust-obscured galaxies and active galactic nuclei, sampling a large range in mass and luminosity, from faint local dwarf galaxies to luminous quasars in the distant Universe. Active galactic nuclei and starburst feedback and feeding mechanisms in distant galaxies will be uncovered through detailed measurements of molecular and atomic line profiles. The SPICA's large-area deep spectrophotometric surveys will provide mid-IR spectra and continuum fluxes for unbiased samples of tens of thousands of galaxies, out to redshifts of z similar to 6.
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| 2. |
- Pallottini, A., et al.
(författare)
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Deep into the structure of the first galaxies : SERRA views
- 2019
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 487:2, s. 1689-1708
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Tidskriftsartikel (refereegranskat)abstract
- We study the formation and evolution of a sample of Lyman break galaxies in the epoch of reionization by using high-resolution (similar to 10 pc), cosmological zoom-in simulations part of the SERRA suite. In SERRA, we follow the interstellar medium thermochemical non-equilibrium evolution and perform on-the-fly radiative transfer of the interstellar radiation field (ISRF). The simulation outputs are post-processed to compute the emission of far infrared lines ([C II], [N II], and [O III]). At z = 8, the most massive galaxy, 'Freesia', has an age t(star) similar or equal to 409 Myr, stellar mass M-star similar or equal to 4.2 x 10(9)M(circle dot), and a star formation rate (SFR), SFR similar or equal to 11.5M(circle dot) yr(-1), due to a recent burst. Freesia has two stellar components (A and B) separated by similar or equal to 2.5 kpc; other 11 galaxies are found within 56.9 +/- 21.6 kpc. The mean ISRF in the Habing band is G = 7.9G(0) and is spatially uniform; in contrast, the ionization parameter is U = 2(-2)(+20) x 10(-3), and has a patchy distribution peaked at the location of star-forming sites. The resulting ionizing escape fraction from Freesia is f(esc) similar or equal to 2 per cent. While [C II] emission is extended (radius 1.54 kpc), [O III] is concentrated in Freesia-Lambda (0.85 kpc), where the ratio Sigma([O III])/Sigma([C II]) similar or equal to 10. As many high-z galaxies, Freesia lies below the local [C II]-SFR relation. We show that this is the general consequence of a starburst phase (pushing the galaxy above the Kennicutt-Schmidt relation) that disrupts/photodissociates the emitting molecular clouds around star-forming sites. Metallicity has a sub-dominant impact on the amplitude of [C II]-SFR deviations.
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| 3. |
- Pallottini, A., et al.
(författare)
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The impact of chemistry on the structure of high-z galaxies
- 2017
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Ingår i: Monthly notices of the Royal Astronomical Society. - : OXFORD UNIV PRESS. - 0035-8711 .- 1365-2966. ; 471:4, s. 4128-4143
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Tidskriftsartikel (refereegranskat)abstract
- To improve our understanding of high-z galaxies, we study the impact of H-2 chemistry on their evolution, morphology and observed properties. We compare two zoom-in high-resolution (30 pc) simulations of prototypical M-star similar to 1010M(circle dot) galaxies at z = 6. The first, 'Dahlia', adopts an equilibrium model for H-2 formation, while the second, 'Alth ae a', features an improved non-equilibrium chemistry network. The star formation rate (SFR) of the two galaxies is similar (within 50 per cent), and increases with time reaching values close to 100M(circle dot) yr(-1) at z = 6. They both have SFR-stellar mass relation consistent with observations, and a specific SFR of similar or equal to 5Gyr(-1). The main differences arise in the gas properties. The non-equilibrium chemistry determines the H -> H-2 transition to occur at densities > 300 cm(-3), i.e. about 10 times larger than predicted by the equilibrium model used for Dahlia. As a result, Alth ae a features a more clumpy and fragmented morphology, in turn makingSNfeedback more effective. Also, because of the lower density and weaker feedback, Dahlia sits 3 sigma away from the Schmidt-Kennicutt relation; Alth ae a, instead nicely agrees with observations. The different gas properties result in widely different observables. Alth ae a outshines Dahlia by a factor of 7 (15) in [C (II)] 157.74 mu m (H(2)17.03 mu m) line emission. Yet, Alth ae a is underluminous with respect to the locally observed [C (II)]-SFR relation. Whether this relation does not apply at high-z or the line luminosity is reduced by cosmic microwave background and metallicity effects remain as an open question.
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| 4. |
- Carniani, S., et al.
(författare)
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Constraints on high-J CO emission lines in z similar to 6 quasars
- 2019
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Ingår i: Monthly notices of the Royal Astronomical Society. - : OXFORD UNIV PRESS. - 0035-8711 .- 1365-2966. ; 489:3, s. 3939-3952
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Tidskriftsartikel (refereegranskat)abstract
- We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of eight highly excited CO (J(up) > 8) lines and continuum emission in two z similar to 6 quasars: SDSS J231038.88+185519.7 (hereafter J2310), for which CO(8-7), CO(9-8), and CO(17-16) lines have been observed, and ULAS J131911.29+095951.4 (J1319), observed in the CO(14-13), CO(17-16), and CO(19-18) lines. The continuum emission of both quasars arises from a compact region (<0.9 kpc). By assuming a modified blackbody law, we estimate dust masses of log(M-dust/M-circle dot) = 8.75 +/- 0.07 and log(M-dust/M-circle dot) = 8.8 +/- 0.2 and dust temperatures of T-dust = 76 +/- 3 K and T-dust = 66(-10)(+15) K, respectively, for J2310 and J1319. Only CO(8-7) and CO(9-8) in J2310 are detected, while 3 sigma upper limits on luminosities are reported for the other lines of both quasars. The CO line luminosities and upper limits measured in J2310 and J1319 are consistent with those observed in local active galactic nuclei and starburst galaxies, and other z similar to 6 quasars, except for SDSS J1148+5251 (J1148), the only quasar at z = 6.4 with a previous CO(17-16) line detection. By computing the CO spectral line energy distributions normalized to the CO(6-5) line and far-infrared luminosities for J2310, J1319, and J1148, we conclude that different gas heating mechanisms (X-ray radiation and/or shocks) may explain the different CO luminosities observed in these z similar to 6 quasar. Future J(up) > 8 CO observations will be crucial to understand the processes responsible for molecular gas excitation in luminous high-z quasars.
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| 5. |
- Carniani, S., et al.
(författare)
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Extended ionised and clumpy gas in a normal galaxy at z=7.1 revealed by ALMA
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 605
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Tidskriftsartikel (refereegranskat)abstract
- We present new ALMA observations of the [O III] 88 mu m line and high angular resolution observations of the [C II] 158 mu m line in a normal star forming galaxy at z = 7.1. Previous [C II] observations of this galaxy had detected [C II] emission consistent with the Ly alpha redshift but spatially slightly off set relative to the optical (UV-rest frame) emission. The new [C II] observations reveal that the [C II] emission is partly clumpy and partly diffuse on scales larger than about 1 kpc. [O III] emission is also detected at high significance, off set relative to the optical counterpart in the same direction as the [C II] clumps, but mostly not overlapping with the bulk of the [C II] emission. The off set between different emission components (optical/UV and different far-IR tracers) is similar to that which is observed in much more powerful starbursts at high redshift. We show that the [O III] emitting clump cannot be explained in terms of diffuse gas excited by the UV radiation emitted by the optical galaxy, but it requires excitation by in-situ (slightly dust obscured) star formation, at a rate of about 7 M circle dot yr(-1). Within 20 kpc from the optical galaxy the ALMA data reveal two additional [O III] emitting systems, which must be star forming companions. We discuss that the complex properties revealed by ALMA in the z similar to 7.1 galaxy are consistent with expectations by recent models and cosmological simulations, in which differential dust extinction, differential excitation and different metal enrichment levels, associated with different subsystems assembling a galaxy, are responsible for the various appearance of the system when observed with distinct tracers.
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| 6. |
- Ferrara, A., et al.
(författare)
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A physical model for [C II] line emission from galaxies
- 2019
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Ingår i: Monthly notices of the Royal Astronomical Society. - : OXFORD UNIV PRESS. - 0035-8711 .- 1365-2966. ; 489:1, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- A tight relation between the [C II] 158 mu m line luminosity and star formation rate is measured in local galaxies. At high redshift (z > 5), though, a much larger scatter is observed, with a considerable (15-20 per cent) fraction of the outliers being [C II]-deficient. Moreover, the [C II] surface brightness (Sigma([C II])) of these sources is systematically lower than expected from the local relation. To clarify the origin of such [C II]-deficiency, we have developed an analytical model that fits local [C II] data and has been validated against radiative transfer simulations performed with CLOUDY. The model predicts an overall increase of Sigma([C II]) with Sigma(SFR). However, for Sigma(SFR) greater than or similar to 1M(circle dot) yr(-1) kpc(-2), Sigma([C II]) saturates. We conclude that underluminous [C II] systems can result from a combination of three factors: (a) large upward deviations from theKennicutt-Schmidt relation (kappa(s) >> 1), parametrized by the 'burstiness' parameter kappa(s); (b) low metallicity; (e.g. CR7). Observations of [C II] emission alone cannot break the degeneracy among the above three parameters; this requires additional information coming from other emission lines (e.g. [OIII]88 mu m, C III]1909 degrees, CO lines). Simple formulae are given to interpret available data for low- and high- z galaxies.
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| 7. |
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| 8. |
- Kohandel, M., et al.
(författare)
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Kinematics of z ≥ 6 galaxies from [C II] line emission
- 2019
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 487:3, s. 3007-3020
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Tidskriftsartikel (refereegranskat)abstract
- We study the kinematical properties of galaxies in the Epoch of Reionization via the [C ii]158 μm line emission. The line profile provides information on the kinematics as well as structural properties such as the presence of a disc and satellites. To understand how these properties are encoded in the line profile, first we develop analytical models from which we identify disc inclination and gas turbulent motions as the key parameters affecting the line profile. To gain further insights, we use 'Althæa', a highly resolved (30\, \rm pc) simulated prototypical Lyman-break galaxy, in the redshift range z = 6-7, when the galaxy is in a very active assembling phase. Based on morphology, we select three main dynamical stages: (I) merger, (II) spiral disc, and (III) disturbed disc. We identify spectral signatures of merger events, spiral arms, and extra-planar flows in (I), (II), and (III), respectively. We derive a generalized dynamical mass versus [C ii]-line FWHM relation. If precise information on the galaxy inclination is (not) available, the returned mass estimate is accurate within a factor 2 (4). A Tully-Fisher relation is found for the observed high-z galaxies, i.e. L[C ii] (FWHM)1.80 ± 0.35 for which we provide a simple, physically based interpretation. Finally, we perform mock ALMA simulations to check the detectability of [C ii]. When seen face-on, Althæa is always detected at >5σ; in the edge-on case it remains undetected because the larger intrinsic FWHM pushes the line peak flux below detection limit. This suggests that some of the reported non-detections might be due to inclination effects.
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| 9. |
- Behrens, C., et al.
(författare)
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Dusty galaxies in the Epoch of Reionization : simulations
- 2018
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 477:1, s. 552-565
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Tidskriftsartikel (refereegranskat)abstract
- The recent discovery of dusty galaxies well into the Epoch of Reionization (redshift z > 6) poses challenging questions about the properties of the interstellar medium in these pristine systems. By combining state-of-the-art hydrodynamic and dust radiative transfer simulations, we address these questions focusing on the recently discovered dusty galaxy A2744_YD4 (z = 8.38, Laporte et al.). We show that we can reproduce the observed spectral energy distribution (SED) only using different physical values with respect to the inferred ones by Laporte et al., i.e. a star formation rate of SFR = 78 M(circle dot)yr(-1), a factor approximate to 4 higher than deduced from simple SED fitting. In this case, we find: (i) dust attenuation (corresponding to tau(v) = 1.4) is consistent with a Milky Way (MW) extinction curve; (ii) the dust-to-metal ratio is low, f(d) similar to 0.08, implying that early dust formation is rather inefficient;(iii) the luminosity-weighted dust temperature is high, T-d = 91 23 K, as a result of the intense (approximate to 100 x MW) interstellar radiation field; and (iv) due to the high T-d, the Atacama Large Millimeter/submillimeter Array Band 7 detection can be explained by a limited dust mass, M-d = 1.6 x 10(6) M-circle dot. Finally, the high dust temperatures might solve the puzzling low infrared excess (IRX) recently deduced for high-z galaxies from the IRX-beta relation.
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| 10. |
- Behrens, C., et al.
(författare)
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Ly alpha emission from galaxies in the Epoch of eionization
- 2019
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 486:2, s. 2197-2209
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Tidskriftsartikel (refereegranskat)abstract
- The intrinsic strength of the Ly alpha line in young, star-forming systems makes it a special tool for studying high-redshift galaxies. However, interpreting observations remains challenging due to the complex radiative transfer involved. Here, we combine state-of-the-art hydrodynamical simulations of 'Althaea', a prototypical Lyman Break Galaxy (LBG; stellar mass M-star similar or equal to 10(10) M-circle dot) at z = 7.2, with detailed radiative transfer computations of dust/continuum, [C II] 158 mu m, and Ly alpha to clarify the relation between the galaxy properties and its Ly alpha emission. Althaea exhibits low (f(alpha) < 1 per cent) Ly alpha escape fractions and equivalent widths, EW less than or similar to 6 angstrom for the simulated lines of sight, with a large scatter. The correlation between escape fraction and inclination is weak, as a result of the rather chaotic structure of high-redshift galaxies. Low f(alpha) values persist even if we artificially remove neutral gas around star-forming regions to mimic the presence of H II regions. The high attenuation is primarily caused by dust clumps co-located with young stellar clusters. We can turn Althaea into a Lyman Alpha Emitter (LAE) only if we artificially remove dust from the clumps, yielding EWs up to 22 angstrom. Our study suggests that the LBG-LAE duty-cycle required by recent clustering measurements poses the challenging problem of a dynamically changing dust attenuation. Finally, we find an anticorrelation between the magnitude of Ly alpha-[C II] line velocity shift and Ly alpha luminosity.
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