| 1. |
- Bianco, Federica B., et al.
(författare)
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Optimization of the Observing Cadence for the Rubin Observatory Legacy Survey of Space and Time : A Pioneering Process of Community-focused Experimental Design
- 2022
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Ingår i: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 258:1
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Tidskriftsartikel (refereegranskat)abstract
- Vera C. Rubin Observatory is a ground-based astronomical facility under construction, a joint project of the National Science Foundation and the U.S. Department of Energy, designed to conduct a multipurpose 10 yr optical survey of the Southern Hemisphere sky: the Legacy Survey of Space and Time. Significant flexibility in survey strategy remains within the constraints imposed by the core science goals of probing dark energy and dark matter, cataloging the solar system, exploring the transient optical sky, and mapping the Milky Way. The survey's massive data throughput will be transformational for many other astrophysics domains and Rubin's data access policy sets the stage for a huge community of potential users. To ensure that the survey science potential is maximized while serving as broad a community as possible, Rubin Observatory has involved the scientific community at large in the process of setting and refining the details of the observing strategy. The motivation, history, and decision-making process of this strategy optimization are detailed in this paper, giving context to the science-driven proposals and recommendations for the survey strategy included in this Focus Issue.
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| 2. |
- Ade, Peter, et al.
(författare)
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The Simons Observatory : science goals and forecasts
- 2019
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Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :2
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Tidskriftsartikel (refereegranskat)abstract
- The Simons Observatory (SO) is a new cosmic microwave background experiment being built on Cerro Toco in Chile, due to begin observations in the early 2020s. We describe the scientific goals of the experiment, motivate the design, and forecast its performance. SO will measure the temperature and polarization anisotropy of the cosmic microwave background in six frequency bands centered at: 27, 39, 93, 145, 225 and 280 GHz. The initial con figuration of SO will have three small-aperture 0.5-m telescopes and one large-aperture 6-m telescope, with a total of 60,000 cryogenic bolometers. Our key science goals are to characterize the primordial perturbations, measure the number of relativistic species and the mass of neutrinos, test for deviations from a cosmological constant, improve our understanding of galaxy evolution, and constrain the duration of reionization. The small aperture telescopes will target the largest angular scales observable from Chile, mapping approximate to 10% of the sky to a white noise level of 2 mu K-arcmin in combined 93 and 145 GHz bands, to measure the primordial tensor-to-scalar ratio, r, at a target level of sigma(r) = 0.003. The large aperture telescope will map approximate to 40% of the sky at arcminute angular resolution to an expected white noise level of 6 mu K-arcmin in combined 93 and 145 GHz bands, overlapping with the majority of the Large Synoptic Survey Telescope sky region and partially with the Dark Energy Spectroscopic Instrument. With up to an order of magnitude lower polarization noise than maps from the Planck satellite, the high-resolution sky maps will constrain cosmological parameters derived from the damping tail, gravitational lensing of the microwave background, the primordial bispectrum, and the thermal and kinematic Sunyaev-Zel'dovich effects, and will aid in delensing the large-angle polarization signal to measure the tensor-to-scalar ratio. The survey will also provide a legacy catalog of 16,000 galaxy clusters and more than 20,000 extragalactic sources.
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| 3. |
- Guaita, Lucia, et al.
(författare)
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Magellan/MMIRS near-infrared multi-object spectroscopy of nebular emission from star-forming galaxies at 2 < z < 3
- 2013
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 551, s. A93-
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Tidskriftsartikel (refereegranskat)abstract
- Aims. To investigate the ingredients, which allow star-forming galaxies to present Ly alpha line in emission, we studied the kinematics and gas phase metallicity of the interstellar medium. Methods. We used multi-object near-infrared spectroscopy with Magellan/MMIRS to study nebular emission from z similar or equal to 2-3 star-forming galaxies discovered in three MUSYC fields. Results. We detected emission lines from four active galactic nuclei and 13 high-redshift star-forming galaxies, including H alpha lines down to a flux of (4 +/- 1)E-17 erg s(-1) cm(-2). This yielded seven new redshifts. The most common emission line detected is [OIII]5007, which is sensitive to metallicity. We were able to measure metallicity (Z) for two galaxies and to set upper (lower) limits for another two (two). The metallicity values are consistent with 0.3 < Z/Z(circle dot) < 1.2, 12 + log (O/H) similar to 8.2-8.8. Comparing the Ly alpha central wavelength with the systemic redshift, we find Delta(vLy alpha-[OIII]5007) = 70 270 km s(-1). Conclusions. High-redshift star-forming galaxies, Ly alpha emitting (LAE) galaxies, and H alpha emitters appear to be located in the low mass, high star-formation rate (SFR) region of the SFR versus stellar mass diagram, confirming that they are experiencing burst episodes of star formation, which are building up their stellar mass. Their metallicities are consistent with the relation found for z <= 2.2 galaxies in the Z versus stellar mass plane. The measured Delta(vLy alpha[OIII]5007) values imply that outflows of material, driven by star formation, could be present in the z similar to 2 3 LAEs of our sample. Comparing with the literature, we note that galaxies with lower metallicity than ours are also characterized by similar Delta(vLy alpha[OIII]5007) velocity off sets. Strong F([OIII]5007) is detected in many Ly alpha emitters. Therefore, we propose the F(Ly alpha)/F([OIII]5007) flux ratio as a tool for the study of high-redshift galaxies; while influenced by metallicity, ionization, and Ly alpha radiative transfer in the ISM, it may be possible to calibrate this ratio to primarily trace one of these effects.
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| 4. |
- Wardlow, J. L., et al.
(författare)
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The LABOCA survey of the Extended Chandra Deep Field-South: a photometric redshift survey of submillimetre galaxies
- 2011
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 415:2, s. 1479-1508
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Tidskriftsartikel (refereegranskat)abstract
- We derive photometric redshifts from 17-band optical to mid-infrared photometry of 78 robust radio, 24-mu m and Spitzer IRAC counterparts to 72 of the 126 submillimetre galaxies (SMGs) selected at 870 mu m by LABOCA observations in the Extended Chandra Deep Field-South (ECDF-S). We test the photometric redshifts of the SMGs against the extensive archival spectroscopy in the ECDF-S. The median photometric redshift of identified SMGs is z = 2.2 +/- 0.1, the standard deviation is sigma(z) = 0.9 and we identify 11 (similar to 15 per cent) high-redshift (z >= 3) SMGs. A statistical analysis of sources in the error circles of unidentified SMGs identifies a population of possible counterparts with a redshift distribution peaking at z = 2.5 +/- 0.2, which likely comprises similar to 60 per cent of the unidentified SMGs. This confirms that the bulk of the undetected SMGs are coeval with those detected in the radio/mid-infrared. We conclude that at most similar to 15 per cent of all the SMGs are below the flux limits of our IRAC observations and thus may lie at z greater than or similar to 3 and hence at most similar to 30 per cent of all SMGs have z greater than or similar to 3. We estimate that the full S(870 mu m) > 4mJy SMG population has a median redshift of 2.5 +/- 0.5. In contrast to previous suggestions, we find no significant correlation between submillimetre flux and redshift. The median stellar mass of the SMGs derived from spectral energy distribution fitting is (9.1 +/- 0.5) x 10(10)M(circle dot) although we caution that the uncertainty in the star formation histories results in a factor of similar to 5 uncertainty in these stellarmasses. Using a single temperature modified blackbody fit with beta = 1.5, the median characteristic dust temperature of SMGs is 37.4 +/- 1.4K. The infrared luminosity function shows that SMGs at z = 2-3 typically have higher far-infrared luminosities and luminosity density than those at z = 1-2. This is mirrored in the evolution of the star formation rate density (SFRD) for SMGs which peaks at z similar to 2. The maximum contribution of bright SMGs to the global SFRD (similar to 5 per cent for SMGs with S(870 mu m) greater than or similar to 4mJy or similar to 50 per cent extrapolated to SMGs with S(870 mu m) > 1mJy) also occurs at z similar to 2.
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| 5. |
- Abolfathi, Bela, et al.
(författare)
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The LSST DESC DC2 Simulated Sky Survey
- 2021
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Ingår i: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 253:31
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Tidskriftsartikel (refereegranskat)abstract
- We describe the simulated sky survey underlying the second data challenge (DC2) carried out in preparation for analysis of the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) by the LSST Dark Energy Science Collaboration (LSST DESC). Significant connections across multiple science domains will be a hallmark of LSST; the DC2 program represents a unique modeling effort that stresses this interconnectivity in a way that has not been attempted before. This effort encompasses a full end-to-end approach: starting from a large N-body simulation, through setting up LSST-like observations including realistic cadences, through image simulations, and finally processing with Rubin's LSST Science Pipelines. This last step ensures that we generate data products resembling those to be delivered by the Rubin Observatory as closely as is currently possible. The simulated DC2 sky survey covers six optical bands in a wide-fast-deep area of approximately 300 deg2, as well as a deep drilling field of approximately 1 deg2. We simulate 5 yr of the planned 10 yr survey. The DC2 sky survey has multiple purposes. First, the LSST DESC working groups can use the data set to develop a range of DESC analysis pipelines to prepare for the advent of actual data. Second, it serves as a realistic test bed for the image processing software under development for LSST by the Rubin Observatory. In particular, simulated data provide a controlled way to investigate certain image-level systematic effects. Finally, the DC2 sky survey enables the exploration of new scientific ideas in both static and time domain cosmology.
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| 6. |
- Martin, Alec, et al.
(författare)
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UV-bright Star-forming Clumps and Their Host Galaxies in UVCANDELS at 0.5 ≤ z ≤ 1
- 2023
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 955:2
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Tidskriftsartikel (refereegranskat)abstract
- Giant star-forming clumps are a prominent feature of star-forming galaxies (SFGs) and contain important clues on galaxy formation and evolution. However, the basic demographics of clumps and their host galaxies remain uncertain. Using the Hubble Space Telescope/Wide Field Camera 3 F275W images from the Ultraviolet Imaging of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, we detect and analyze giant star-forming clumps in galaxies at 0.5 ≤ z ≤ 1, connecting two epochs when clumps are common (at cosmic high noon, z ∼ 2) and rare (in the local Universe). We construct a clump sample whose rest-frame 1600 Å luminosity is 3 times higher than the most luminous local H ii regions (MUV ≤ −16 AB). In our sample, 35% ± 3% of low-mass galaxies (log[M∗/M⊙] < 10) are clumpy (i.e., containing at least one off-center clump). This fraction changes to 22% ± 3% and 22% ± 4% for intermediate (10 ≤ log[M∗/M⊙] ≤ 10.5) and high-mass (log[M∗/M⊙] > 10.5) galaxies, in agreement with previous studies. When compared to similar-mass nonclumpy SFGs, low- and intermediate-mass clumpy SFGs tend to have higher star formation rates (SFRs) and bluer rest-frame U − V colors, while high-mass clumpy SFGs tend to be larger than nonclumpy SFGs. However, clumpy and nonclumpy SFGs have similar Sérsic index, indicating a similar underlying density profile. Furthermore, we investigate how the UV luminosity of star-forming regions correlates with the physical properties of host galaxies. On average, more luminous star-forming regions reside in more luminous, smaller, and/or higher specific SFR galaxies and are found closer to their hosts' galactic centers.
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| 7. |
- Mehta, Vihang, et al.
(författare)
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A Spatially Resolved Analysis of Star Formation Burstiness by Comparing UV and Hα in Galaxies at z ∼ 1 with UVCANDELS
- 2023
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 952:2
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Tidskriftsartikel (refereegranskat)abstract
- The UltraViolet imaging of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey Fields (UVCANDELS) program provides Hubble Space Telescope (HST)/UVIS F275W imaging for four CANDELS fields. We combine this UV imaging with existing HST/near-IR grism spectroscopy from 3D-HST+AGHAST to directly compare the resolved rest-frame UV and Hα emission for a sample of 979 galaxies at 0.7 < z < 1.5, spanning a range in stellar mass of 108−11.5M⊙. Using a stacking analysis, we perform a resolved comparison between homogenized maps of rest-UV and Hα to compute the average UV-to-Hα luminosity ratio (an indicator of burstiness in star formation) as a function of galactocentric radius. We find that galaxies below stellar mass of ∼109.5M⊙, at all radii, have a UV-to-Hα ratio higher than the equilibrium value expected from constant star formation, indicating a significant contribution from bursty star formation. Even for galaxies with stellar mass ≳109.5M⊙, the UV-to-Hα ratio is elevated toward their outskirts (R/Reff > 1.5), suggesting that bursty star formation is likely prevalent in the outskirts of even the most massive galaxies, but is likely overshadowed by their brighter cores. Furthermore, we present the UV-to-Hα ratio as a function of galaxy surface brightness, a proxy for stellar mass surface density, and find that regions below ∼107.5M⊙ kpc−2 are consistent with bursty star formation, regardless of their galaxy stellar mass, potentially suggesting that local star formation is independent of global galaxy properties at the smallest scales. Last, we find galaxies at z > 1.1 to have bursty star formation, regardless of radius or surface brightness.
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| 8. |
- Sattari, Zahra, et al.
(författare)
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Fraction of Clumpy Star-forming Galaxies at 0.5 ≤ z ≤ 3 in UVCANDELS : Dependence on Stellar Mass and Environment
- 2023
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 951:2
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Tidskriftsartikel (refereegranskat)abstract
- High-resolution imaging of galaxies in rest-frame UV has revealed the existence of giant star-forming clumps prevalent in high-redshift galaxies. Studying these substructures provides important information about their formation and evolution and informs theoretical galaxy evolution models. We present a new method to identify clumps in galaxies' high-resolution rest-frame UV images. Using imaging data from CANDELS and UVCANDELS, we identify star-forming clumps in an HST/F160W ≤ 25 AB mag sample of 6767 galaxies at 0.5 ≤ z ≤ 3 in four fields, GOODS-N, GOODS-S, EGS, and COSMOS. We use a low-passband filter in Fourier space to reconstruct the background image of a galaxy and detect small-scale features (clumps) on the background-subtracted image. Clumpy galaxies are defined as those having at least one off-center clump that contributes a minimum of 10% of the galaxy's total rest-frame UV flux. We measure the fraction of clumpy galaxies (fclumpy) as a function of stellar mass, redshift, and galaxy environment. Our results indicate that fclumpy increases with redshift, reaching ∼65% at z ∼ 1.5. We also find that fclumpy in low-mass galaxies () is 10% higher compared to that of their high-mass counterparts (). Moreover, we find no evidence of significant environmental dependence of fclumpy for galaxies at the redshift range of this study. Our results suggest that the fragmentation of gas clouds under violent disk instability remains the primary driving mechanism for clump formation, and incidents common in dense environments, such as mergers, are not the dominant processes.
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| 9. |
- Zheng, Zhen-Ya, et al.
(författare)
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X-RAY CONSTRAINTS ON THE Ly alpha ESCAPE FRACTION
- 2012
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 746:1
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Tidskriftsartikel (refereegranskat)abstract
- We have co-added the X-ray flux of all known Lya emitters (LAEs) in the 4 Ms Chandra Deep Field South (CDF-S) region, achieving the tightest upper limits yet on the X-ray to Lya ratio. We use the X-ray data to place sensitive upper limits on the average unobscured star formation rate (SFRX) in these galaxies. A very small fraction of Lya galaxies in the field are individually detected in the X-rays, implying a low fraction of active galactic nucleus activity. After excluding the few X-ray-detected LAEs, we stack the undetected LAEs located in the 4 Ms CDF-S data and 250 ks Extended CDF-S (ECDF-S) data, and compute a 1 sigma upper limit on SFRX < 1.6, 14, 28, 28, 140, 440, 880M(circle dot) yr(-1) for LAEs located at z similar to 0.3 and z = 2.1, 3.1, 3.2, 4.5, 5.7, and 6.5, respectively. The upper limit of SFRX in LAEs can be then compared to SFRLy alpha derived from Lya line and thus can constrain on the Lya escape fraction (f(Ly alpha)(Esc)). The f(Ly alpha)(Esc) from X-ray at z similar to 0.3 is substantially larger than that from UV or H alpha. Three X-ray-detected LAE galaxies at z similar to 0.3 show f(Ly alpha)(Esc) similar to 3%-22%, and the average Ly alpha escape fraction from stacking the X-ray-undetected LAEs show f(Ly alpha)(Esc) > 28% at 3 sigma significance level at the same redshift. We derive a lower limit on f(Ly alpha)(Esc) > 14% (84% confidence level, 1 sigma lower limit) for LAEs at redshift z similar to 2.1 and z similar to 3.1-3.2. At z > 4, the current LAE samples are not of sufficient size to constrain SFRX well. By averaging all the LAEs at z > 2, the X-ray non-detection constrains f(Ly alpha)(Esc)17% (84% confidence level, 1 sigma lower limit), and rejects f(Ly alpha)(Esc) < 5.7% at the 99.87% confidence level from 2.1 < z < 6.5.
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