We present Atacama Large Millimeter/submillimeter Array (ALMA) 860 mu m imaging of four high-redshift (z = 2.8-5.7) dusty sources that were detected using the South Pole Telescope (SPT) at 1.4 mm and ...are not seen in existing radio to far-infrared catalogs. At 1".5 resolution, the ALMA data reveal multiple images of each submillimeter source, separated by l"-3", consistent with strong lensing by intervening galaxies visible in near-IR imaging of these sources. We describe a gravitational lens modeling procedure that operates on the measured visibilities and incorporates self-calibration-like antenna phase corrections as part of the model optimization, which we use to interpret the source structure. Lens models indicate that SPT0346-52, located at z = 5.7, is one of the most luminous and intensely star-forming sources in the universe with a lensing corrected FIR luminosity of 3.7 x 10 super(13) L sub(middot in circle) and star formation surface density of 4200 M sub(middot in circle) yr super(-1) kpc super(-2). We find magnification factors of 5 to 22, with lens Einstein radii of 1".1-2".0 and Einstein enclosed masses of 1.6-7.2 x 10 super(11) M sub(middot in circle). These observations confirm the lensing origin of these objects, allow us to measure their intrinsic sizes and luminosities, and demonstrate the important role that ALMA will play in the interpretation of lensed submillimeter sources.
Euclid preparation Pocino, A.; Tutusaus, I.; Fosalba, P. ...
Astronomy and astrophysics (Berlin),
11/2021, Volume:
655
Journal Article
Peer reviewed
Open access
Photometric redshifts (photo-
z
s) are one of the main ingredients in the analysis of cosmological probes. Their accuracy particularly affects the results of the analyses of galaxy clustering with ...photometrically selected galaxies (GC
ph
) and weak lensing. In the next decade, space missions such as
Euclid
will collect precise and accurate photometric measurements for millions of galaxies. These data should be complemented with upcoming ground-based observations to derive precise and accurate photo-
z
s. In this article we explore how the tomographic redshift binning and depth of ground-based observations will affect the cosmological constraints expected from the
Euclid
mission. We focus on GC
ph
and extend the study to include galaxy-galaxy lensing (GGL). We add a layer of complexity to the analysis by simulating several realistic photo-
z
distributions based on the
Euclid
Consortium Flagship simulation and using a machine learning photo-
z
algorithm. We then use the Fisher matrix formalism together with these galaxy samples to study the cosmological constraining power as a function of redshift binning, survey depth, and photo-
z
accuracy. We find that bins with an equal width in redshift provide a higher figure of merit (FoM) than equipopulated bins and that increasing the number of redshift bins from ten to 13 improves the FoM by 35% and 15% for GC
ph
and its combination with GGL, respectively. For GC
ph
, an increase in the survey depth provides a higher FoM. However, when we include faint galaxies beyond the limit of the spectroscopic training data, the resulting FoM decreases because of the spurious photo-
z
s. When combining GC
ph
and GGL, the number density of the sample, which is set by the survey depth, is the main factor driving the variations in the FoM. Adding galaxies at faint magnitudes and high redshift increases the FoM, even when they are beyond the spectroscopic limit, since the number density increase compensates for the photo-
z
degradation in this case. We conclude that there is more information that can be extracted beyond the nominal ten tomographic redshift bins of
Euclid
and that we should be cautious when adding faint galaxies into our sample since they can degrade the cosmological constraints.
Aims. The role of galaxy mergers in massive galaxy evolution, and in particular to mass assembly and size growth, remains an open question. In this paper we measure the merger fraction and rate, both ...minor and major, of massive early-type galaxies (M ⋆ ≥ 1011 M⊙) in the COSMOS field, and study their role in mass and size evolution. Methods. We used the 30-band photometric catalogue in COSMOS, complemented with the spectroscopy of the zCOSMOS survey, to define close pairs with a separation on the sky plane 10 h-1 kpc ≤ rp ≤ 30 h-1 kpc and a relative velocity Δv ≤ 500 km s-1 in redshift space. We measured both major (stellar mass ratio μ ≡ M ⋆ ,2/M ⋆ ,1 ≥ 1/4) and minor (1/10 ≤ μ < 1/4) merger fractions of massive galaxies, and studied their dependence on redshift and on morphology (early types vs. late types). Results. The merger fraction and rate of massive galaxies evolves as a power-law (1 + z)n, with major mergers increasing with redshift, nMM = 1.4, and minor mergers showing little evolution, nmm ~ 0. When split by their morphology, the minor merger fraction for early-type galaxies (ETGs) is higher by a factor of three than that for late-type galaxies (LTGs), and both are nearly constant with redshift. The fraction of major mergers for massive LTGs evolves faster (nMMLT ~ 4 ) than for ETGs (nMMET= 1.8). Conclusions. Our results show that massive ETGs have undergone 0.89 mergers (0.43 major and 0.46 minor) since z ~ 1, leading to a mass growth of ~30%. We find that μ ≥ 1/10 mergers can explain ~55% of the observed size evolution of these galaxies since z ~ 1. Another ~20% is due to the progenitor bias (younger galaxies are more extended) and we estimate that very minor mergers (μ < 1/10) could contribute with an extra ~20%. The remaining ~5% should come from other processes (e.g., adiabatic expansion or observational effects). This picture also reproduces the mass growth and the velocity dispersion evolution of these galaxies. We conclude from these results, and after exploring all the possible uncertainties in our picture, that merging is the main contributor to the size evolution of massive ETGs at z ≲ 1, accounting for ~50−75% of that evolution in the last 8 Gyr. Nearly half of the evolution due to mergers is related to minor (μ < 1/4) events.
Context. The standard cosmological model is based on the fundamental assumptions of a spatially homogeneous and isotropic universe on large scales. An observational detection of a violation of these ...assumptions at any redshift would immediately indicate the presence of new physics.
Aims. We quantify the ability of the Euclid mission, together with contemporary surveys, to improve the current sensitivity of null tests of the canonical cosmological constant Λ and the cold dark matter (ΛCDM) model in the redshift range 0 < z < 1.8.
Methods. We considered both currently available data and simulated Euclid and external data products based on a ΛCDM fiducial model, an evolving dark energy model assuming the Chevallier-Polarski-Linder parameterization or an inhomogeneous Lemaître-Tolman-Bondi model with a cosmological constant Λ, and carried out two separate but complementary analyses: a machine learning reconstruction of the null tests based on genetic algorithms, and a theory-agnostic parametric approach based on Taylor expansion and binning of the data, in order to avoid assumptions about any particular model.
Results. We find that in combination with external probes, Euclid can improve current constraints on null tests of the ΛCDM by approximately a factor of three when using the machine learning approach and by a further factor of two in the case of the parametric approach. However, we also find that in certain cases, the parametric approach may be biased against or missing some features of models far from ΛCDM.
Conclusions. Our analysis highlights the importance of synergies between Euclid and other surveys. These synergies are crucial for providing tighter constraints over an extended redshift range for a plethora of different consistency tests of some of the main assumptions of the current cosmological paradigm.
ABSTRACT To understand cosmic mass assembly in the universe at early epochs, we primarily rely on measurements of the stellar masses and star formation rates (SFRs) of distant galaxies. In this ...paper, we present stellar masses and SFRs of six high-redshift (2.8 ≤ z ≤ 5.7) dusty, star-forming galaxies (DSFGs) that are strongly gravitationally lensed by foreground galaxies. These sources were first discovered by the South Pole Telescope (SPT) at millimeter wavelengths and all have spectroscopic redshifts and robust lens models derived from Atacama Large Millimeter/submillimeter Array observations. We have conducted follow-up observations to obtain multi-wavelength imaging data using the Hubble Space Telescope (HST), Spitzer, Herschel, and the Atacama Pathfinder EXperiment. We use the high-resolution HST/Wide Field Camera 3 images to disentangle the background source from the foreground lens in Spitzer/IRAC data. The detections and upper limits provide important constraints on the spectral energy distributions (SEDs) for these DSFGs, yielding stellar masses, IR luminosities, and SFRs. The SED fits of six SPT sources show that the intrinsic stellar masses span a range more than one order of magnitude with a median value ∼5 ×1010 M . The intrinsic IR luminosities range from 4 × 1012 L to 4 × 1013 L . They all have prodigious intrinsic SFRs of 510-4800 M yr−1. Compared to the star-forming main sequence (MS), these six DSFGs have specific SFRs that all lie above the MS, including two galaxies that are a factor of 10 higher than the MS. Our results suggest that we are witnessing ongoing strong starburst events that may be driven by major mergers.
We present ALMA detections of the NII 205 μm and CO(12−11) emission lines, and the tentative detection of CI 3P1–3P0 for the strongly lensed (μ = 5.7 ± 0.5) dusty, star-forming galaxy SPT-S ...J213242-5802.9 (hereafter SPT2132-58) at z = 4.77. The NII and CO(12−11) lines are detected at 11.5 and 8.5σ levels, respectively, by our band 6 observations. The CI line is detected at 3.2σ after a reanalysis of existing band 3 data. The CI luminosity implies a gas mass of (3.8 ± 1.2) × 1010M⊙, and, consequently, a very short depletion timescale of 34 ± 13 Myr and a CO luminosity to gas mass conversion factor αCO of 1.0 ± 0.3 M⊙ (K km s-1 pc2)-1. SPT2132-58 is an extreme starburst with an intrinsic star formation rate of 1100 ± 200 M⊙/yr. We find a CII/NII ratio of 26 ± 6, which is the highest ratio reported at z > 4. This suggests that SPT2132-58 hosts an evolved interstellar medium (0.5 Z⊙< Z < 1.5 Z⊙), which may be dominated by photodissociation regions. The CO(2−1) and CO(5−4) transitions have lower CO to far-infrared ratios than local and high-redshift samples, while CO(12−11) is similar to these samples, suggesting the presence of an additional very excited component or an active galactic nucleus.
Spot the difference Noresco, M; Pozzetti, L; Cimatti, A ...
Astronomy and astrophysics (Berlin),
10/2013, Volume:
558
Journal Article
Peer reviewed
Open access
We present the analysis of photometric, spectroscopic, and morphological properties for differently selected samples of passive galaxies up to z=1 extracted from the zCOSMOS-20k spectroscopic survey. ...This analysis intends to explore the dependence of galaxy properties on the selection criterion adopted, study the degree of contamination due to star-forming outliers, and provide a comparison between different commonly used selection criteria. This work is a first step fully investigating the selection effects of passive galaxies for future massive surveys such as Euclid. By studying the restframe color-mass and color diagrams, we provided two revised definitions of passive galaxies based on these criteria that better reproduce the observed bimodality in the properties of zCOSMOS -20k galaxies.
Euclid preparation Saglia, R.; Galametz, A.; Paltani, S. ...
Astronomy and astrophysics (Berlin),
10/2020, Volume:
642
Journal Article
Peer reviewed
Open access
The Complete Calibration of the Colour–Redshift Relation survey (C3R2) is a spectroscopic effort involving ESO and Keck facilities designed specifically to empirically calibrate the galaxy ...colour–redshift relation –
P
(
z
|
C
) to the
Euclid
depth (
i
AB
= 24.5) and is intimately linked to the success of upcoming Stage IV dark energy missions based on weak lensing cosmology. The aim is to build a spectroscopic calibration sample that is as representative as possible of the galaxies of the
Euclid
weak lensing sample. In order to minimise the number of spectroscopic observations necessary to fill the gaps in current knowledge of the
P
(
z
|
C
), self-organising map (SOM) representations of the galaxy colour space have been constructed. Here we present the first results of an ESO@VLT Large Programme approved in the context of C3R2, which makes use of the two VLT optical and near-infrared multi-object spectrographs, FORS2 and KMOS. This data release paper focuses on high-quality spectroscopic redshifts of high-redshift galaxies observed with the KMOS spectrograph in the near-infrared
H
- and
K
-bands. A total of 424 highly-reliable redshifts are measured in the 1.3 ≤
z
≤ 2.5 range, with total success rates of 60.7% in the
H
-band and 32.8% in the
K
-band. The newly determined redshifts fill 55% of high (mainly regions with no spectroscopic measurements) and 35% of lower (regions with low-resolution/low-quality spectroscopic measurements) priority empty SOM grid cells. We measured H
α
fluxes in a 1.″2 radius aperture from the spectra of the spectroscopically confirmed galaxies and converted them into star formation rates. In addition, we performed an SED fitting analysis on the same sample in order to derive stellar masses,
E
(
B
−
V
), total magnitudes, and SFRs. We combine the results obtained from the spectra with those derived via SED fitting, and we show that the spectroscopic failures come from either weakly star-forming galaxies (at
z
< 1.7, i.e. in the
H
-band) or low S/N spectra (in the
K
-band) of
z
> 2 galaxies.
Context.
The standard cosmological model is based on the fundamental assumptions of a spatially homogeneous and isotropic universe on large scales. An observational detection of a violation of these ...assumptions at any redshift would immediately indicate the presence of new physics.
Aims.
We quantify the ability of the
Euclid
mission, together with contemporary surveys, to improve the current sensitivity of null tests of the canonical cosmological constant Λ and the cold dark matter (ΛCDM) model in the redshift range 0 <
z
< 1.8.
Methods.
We considered both currently available data and simulated
Euclid
and external data products based on a ΛCDM fiducial model, an evolving dark energy model assuming the Chevallier-Polarski-Linder parameterization or an inhomogeneous Lemaître-Tolman-Bondi model with a cosmological constant Λ, and carried out two separate but complementary analyses: a machine learning reconstruction of the null tests based on genetic algorithms, and a theory-agnostic parametric approach based on Taylor expansion and binning of the data, in order to avoid assumptions about any particular model.
Results.
We find that in combination with external probes,
Euclid
can improve current constraints on null tests of the ΛCDM by approximately a factor of three when using the machine learning approach and by a further factor of two in the case of the parametric approach. However, we also find that in certain cases, the parametric approach may be biased against or missing some features of models far from ΛCDM.
Conclusions.
Our analysis highlights the importance of synergies between
Euclid
and other surveys. These synergies are crucial for providing tighter constraints over an extended redshift range for a plethora of different consistency tests of some of the main assumptions of the current cosmological paradigm.
The application of multi-wavelength selection techniques is essential for obtaining a complete and unbiased census of active galactic nuclei (AGN). We present here a method for selecting zeta similar ...1 obscured AGN from optical spectroscopic surveys. A sample of 94 narrow-line AGN with 0:65 lessthan zeta lessthan 1:20 was selected from the 20k-Bright zCOSMOS galaxy sample by detection of the high-ionization Nev lambda3426 line. The presence of this emission line in a galaxy spectrum is indicative of nuclear activity, although the selection is biased toward low absorbing column densities on narrow-line region or galactic scales. A similar sample of unobscured was collected applying the same analysis to zCOSMOS broad-line objects. This paper presents and compares the optical spectral properties of the two AGN samples. Finally, a previously developed diagnostic, based on the X-ray-to-Nev luminosity ratio, was exploited to search for the more heavily obscured AGN. We found that Nev-selected narrow-line AGN have Seyfert 2-like optical spectra, although their emission line ratios are diluted by a star-forming component.
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