| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- Lochner, Michelle, et al.
(författare)
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The Impact of Observing Strategy on Cosmological Constraints with LSST
- 2022
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Ingår i: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 259:2
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Tidskriftsartikel (refereegranskat)abstract
- The generation-defining Vera C. Rubin Observatory will make state-of-the-art measurements of both the static and transient universe through its Legacy Survey for Space and Time (LSST). With such capabilities, it is immensely challenging to optimize the LSST observing strategy across the survey's wide range of science drivers. Many aspects of the LSST observing strategy relevant to the LSST Dark Energy Science Collaboration, such as survey footprint definition, single-visit exposure time, and the cadence of repeat visits in different filters, are yet to be finalized. Here, we present metrics used to assess the impact of observing strategy on the cosmological probes considered most sensitive to survey design; these are large-scale structure, weak lensing, type Ia supernovae, kilonovae, and strong lens systems (as well as photometric redshifts, which enable many of these probes). We evaluate these metrics for over 100 different simulated potential survey designs. Our results show that multiple observing strategy decisions can profoundly impact cosmological constraints with LSST; these include adjusting the survey footprint, ensuring repeat nightly visits are taken in different filters, and enforcing regular cadence. We provide public code for our metrics, which makes them readily available for evaluating further modifications to the survey design. We conclude with a set of recommendations and highlight observing strategy factors that require further research.
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| 5. |
- Acquaviva, Viviana, et al.
(författare)
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THE CURIOUS CASE OF Ly alpha EMITTERS : GROWING YOUNGER FROM z similar to 3 to z similar to 2?
- 2012
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Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 751:2
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Tidskriftsartikel (refereegranskat)abstract
- Ly alpha emitting (LAE) galaxies are thought to be progenitors of present-day L* galaxies. Clustering analyses have suggested that LAEs at z similar to 3 might evolve into LAEs at z similar to 2, but it is unclear whether the physical nature of these galaxies is compatible with this hypothesis. Several groups have investigated the properties of LAEs using spectral energy distribution (SED) fitting, but direct comparison of their results is complicated by inconsistencies in the treatment of the data and in the assumptions made in modeling the stellar populations, which are degenerate with the effects of galaxy evolution. By using the same data analysis pipeline and SED fitting software on two stacked samples of LAEs at z = 3.1 and z = 2.1, and by eliminating several systematic uncertainties that might cause a discrepancy, we determine that the physical properties of these two samples of galaxies are dramatically different. LAEs at z = 3.1 are found to be old (age similar to 1 Gyr) and metal-poor (Z < 0.2 Z(circle dot)), while LAEs at z = 2.1 appear to be young (age similar to 50 Myr) and metal-rich (Z > Z(circle dot)). The difference in the observed stellar ages makes it very unlikely that z = 3.1 LAEs evolve directly into z = 2.1 LAEs. Larger samples of galaxies, studies of individual objects, and spectroscopic measurements of metallicity at these redshifts are needed to confirm this picture, which is difficult to reconcile with the effects of 1 Gyr of cosmological evolution.
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| 6. |
- Berry, Michael, et al.
(författare)
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STACKED REST-FRAME ULTRAVIOLET SPECTRA OF Ly alpha-EMITTING AND CONTINUUM-SELECTED GALAXIES AT 2 < z < 3.5
- 2012
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 749:1, s. 4-
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Tidskriftsartikel (refereegranskat)abstract
- We present properties of individual and composite rest-UV spectra of continuum-and narrowband-selected star-forming galaxies (SFGs) at a redshift of 2 < z < 3.5 discovered by the MUSYC collaboration in the Extended Chandra Deep Field-South. Among our sample of 81 UV-bright SFGs, 59 have R < 25.5, of which 32 have rest-frame equivalent widths of W-Ly alpha > 20 angstrom, the canonical limit to be classified as an Ly alpha-emitting galaxy. We divide our data set into subsamples based on properties that we are able to measure for each individual galaxy: Ly alpha equivalent width, rest-frame UV colors, and redshift. Among our subsample of galaxies with R < 25.5, those with rest frame W-Ly alpha > 20 angstrom have bluer UV continua, weaker low-ionization interstellar absorption lines, weaker C IV absorption, and stronger Si II* nebular emission than those with W-Ly alpha < 20 angstrom. We measure a velocity offset of Delta nu similar to 600 km s(-1) between Ly alpha emission and low-ionization absorption, which does not vary substantially among any of our subsamples. We find that the interstellar component, as opposed to the stellar component, dominates the high-ionization absorption line profiles. We find that the low-and high-ionization Si ionization states have similar kinematic properties, yet the low-ionization absorption is correlated with Ly alpha emission and the high-ionization absorption is not. These trends are consistent with outflowing neutral gas being in the form of neutral clouds embedded in ionized gas as previously suggested by Steidel et al. Moreover, our galaxies with bluer UV colors have stronger Ly alpha emission, weaker low-ionization absorption, and more prominent nebular emission line profiles. From a redshift of 2.7 < z < 3.5 to 2.0 < z < 2.7, our subsample of galaxies with W-Ly alpha < 20 angstrom shows no significant evolution in their physical properties or the nature of their outflows. Among our data set, UV-bright galaxies with W-Ly alpha > 20 angstrom exhibit weaker Ly alpha emission at lower redshifts, although we caution that this could be caused by spectroscopic confirmation of low Ly alpha equivalent width galaxies being harder at z similar to 3 than z similar to 2.
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| 7. |
- Bond, Nicholas A., et al.
(författare)
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EVOLUTION IN THE CONTINUUM MORPHOLOGICAL PROPERTIES OF Ly alpha-EMITTING GALAXIES FROM z=3.1 TO z=2.1
- 2012
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 753:2, s. 95-
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Tidskriftsartikel (refereegranskat)abstract
- We present a rest-frame ultraviolet morphological analysis of 108 z similar or equal to 2.1 Ly alpha emitters (LAEs) in the Extended Chandra Deep Field South and compare it to a similar sample of 171 LAEs at z similar or equal to 3.1. Using Hubble Space Telescope images from the Galaxy Evolution from Morphology and SEDs survey, Great Observatories Origins Deep Survey, and Hubble Ultradeep Field, we measure size and photometric component distributions, where photometric components are defined as distinct clumps of UV-continuum emission. At both redshifts, >80% of LAEs have observed half-light radii < 2 kpc, but the median half-light radius rises from 0.95 +/- 0.04 kpc at z = 3.1 to 1.41 +/- 0.14 kpc at z = 2.1. A similar evolution is seen in the sizes of individual rest-UV components, but there is no evidence for evolution in the number of multi-component systems. In the z = 2.1 sample, we see clear correlations between the size of an LAE and other physical properties derived from its spectral energy distribution (SED). LAEs are found to be larger for galaxies with higher stellar mass, star formation rate, and dust obscuration, but there is no evidence for a trend between equivalent width and half-light radius at either redshift. The presence of these correlations suggests that a wide range of objects are being selected by LAE surveys at z similar or equal to 2, including a significant fraction of objects for which a massive and moderately extended population of old stars underlies the young starburst giving rise to the Ly alpha emission.
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| 8. |
- Feldmeier, John J., et al.
(författare)
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SEARCHING FOR NEUTRAL HYDROGEN HALOS AROUND z similar to 2.1 AND z similar to 3.1 Ly alpha EMITTING GALAXIES
- 2013
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 776:2, s. 75-
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Tidskriftsartikel (refereegranskat)abstract
- We search for evidence of diffuse Ly alpha emission from extended neutral hydrogen surrounding Ly alpha emitting galaxies (LAEs) using deep narrow-band images of the Extended Chandra Deep Field South. By stacking the profiles of 187 LAEs at z = 2.06, 241 LAEs at z = 3.10, and 179 LAEs at z = 3.12, and carefully performing low-surface brightness photometry, we obtain mean surface brightness maps that reach 9.9, 8.7, and 6.2 x 10(-19) erg cm(-2) s(-1) arcsec(-2) in the emission line. We undertake a thorough investigation of systematic uncertainties in our surface brightness measurements and find that our limits are 5-10 times larger than would be expected from Poisson background fluctuations; these uncertainties are often underestimated in the literature. At z similar to 3.1, we find evidence for extended halos with small-scale lengths of 5-8 kpc in some but not all of our sub-samples. We demonstrate that sub-samples of LAEs with low equivalent widths and brighter continuum magnitudes are more likely to possess such halos. At z similar to 2.1, we find no evidence of extended Ly alpha emission down to our detection limits. Through Monte-Carlo simulations, we also show that we would have detected large diffuse LAE halos if they were present in our data sets. We compare these findings to other measurements in the literature and discuss possible instrumental and astrophysical reasons for the discrepancies.
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| 9. |
- Guaita, Lucia, et al.
(författare)
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Ly alpha-EMITTING GALAXIES AT z=2.1 : STELLAR MASSES, DUST, AND STAR FORMATION HISTORIES FROM SPECTRAL ENERGY DISTRIBUTION FITTING
- 2011
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 733:2, s. 114-
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Tidskriftsartikel (refereegranskat)abstract
- We study the physical properties of 216 z similar or equal to 2.1 Ly alpha-emitting galaxies (LAEs) discovered in an ultra-deep narrow-MUSYC image of the ECDF-S. We fit their stacked spectral energy distribution (SED) using Charlot & Bruzual templates. We consider star formation histories (SFHs) parameterized by the e-folding time parameter tau, allowing for exponentially decreasing (tau > 0), exponentially increasing (tau < 0), and constant star formation rates (SFRs). We estimated the average flux at 5015 angstrom of our LAE sample, finding a non-detection, which translates into negligible He II line emission at z similar or equal to 2.1. In addition to this, the lack of high equivalent width (EW) Ly alpha line objects ruled out the hypothesis of a top-heavy initial mass function in LAEs. The typical LAEs of our sample are characterized by best-fit parameters and 68% confidence intervals of log(M(*)/M(circle dot)) = 8.6[8.4-9.1], E(B - V) = 0.22[0.00-0.31], tau = -0.02[(-4)-18] Gyr, and age(SF) = 0.018[0.009-3] Gyr. Thus, we obtain robust measurements of low stellar mass and dust content, but we cannot place meaningful constraints on the age or SFH of the LAEs. We also calculate the instantaneous SFR to be 35[0.003-170] M(circle dot) yr(-1), with its average over the last 100 Myr before observation giving < SFR >(100) = 4[2-30] M(circle dot) yr(-1). When we compare the results for the same SFH, typical LAEs at z similar or equal to 2.1 appear dustier and show higher instantaneous SFRs than z similar or equal to 3.1 LAEs, while the observed stellar masses of the two samples seem consistent. Because the majority are low-mass galaxies, our typical LAEs appear to occupy the low-mass end of the distribution of star-forming galaxies at z similar or equal to 2. We perform SED fitting on several sub-samples selected based on photometric properties and find that LAE sub-samples at z similar or equal to 2.1 exhibit heterogeneous properties. The typical IRAC-bright, UV-bright, and red LAEs have the largest stellar mass and dust reddening. The typical UV-faint, IRAC-faint, and high EW LAE sub-samples appear less massive (<10(9) M(circle dot)) and less dusty, with E(B - V) consistent with zero.
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| 10. |
- Kuschel, Maxwell, et al.
(författare)
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Investigating the Dominant Environmental Quenching Process in UVCANDELS/COSMOS Groups
- 2023
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 947:1
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Tidskriftsartikel (refereegranskat)abstract
- We explore how the fraction of quenched galaxies changes in groups of galaxies with respect to the distance to the center of the group, redshift, and stellar mass to determine the dominant process of environmental quenching in 0.2 < z < 0.8 groups. We use new UV data from the UVCANDELS project in addition to existing multiband photometry to derive new galaxy physical properties of the group galaxies from the zCOSMOS 20 k group catalog. Limiting our analysis to a complete sample of log (M*/M⊙) > 10.56 group galaxies, we find that the probability of being quenched increases slowly with decreasing redshift, diverging from the stagnant field galaxy population. A corresponding analysis on how the probability of being quenched increases with time within groups suggests that the dominant environmental quenching process is characterized by slow (∼Gyr) timescales. We find a quenching time of approximately Gyr, consistent with the slow processes of strangulation and delayed-then-rapid quenching although more data are needed to confirm this result.
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