J/ApJ/927/164 Stellar population properties from LEGA-C DR2 (Borghi+, 2022)
Toward a better understanding of cosmic chronometers: stellar population
properties of passive galaxies at intermediate redshift.
Borghi N., Moresco M., Cimatti A., Huchet A., Quai S., Pozzetti L.
<Astrophys. J., 927, 164 (2022)>
=2022ApJ...927..164B 2022ApJ...927..164B
ADC_Keywords: Galaxies, spectra; Abundances; Stars, ages; Optical
Keywords: Galaxy evolution ; Galaxy abundances ; Galaxy ages ;
Observational cosmology
Abstract:
We take advantage of the publicly available LEGA-C spectroscopic
survey to measure the stellar population properties of 140 individual
massive and passive galaxies at z∼0.7. We develop and publicly release
PyLick, a flexible Python code to measure UV to near-IR spectral
indices. With PyLick we study the H/K ratio as a new diagnostic based
on the pseudo-Lick CaII H and K indices and find that a cut in H/K<1.1
can be used jointly with other criteria to select (or verify the
purity of) samples of passive galaxies. By combining photometric and
spectroscopic criteria, we select a reliable sample of passively
evolving galaxies. We constrain single-burst stellar ages,
metallicities [Z/H], and [α/Fe] with an optimized set of Lick
indices, exploring in detail the robustness of our measurement against
different combinations. Even without imposing cosmological priors, the
derived ages follow a clear trend compatible with the expected
cosmological aging of the universe. We observe no significant redshift
evolution for the metal abundance with respect to the values derived
at z=0, with median [Z/H]=0.08±0.18 and [α/Fe]=0.13±0.11.
Finally, we analyze the relations between log age, [Z/H],
[α/Fe], and the stellar velocity dispersion, finding slopes of
(0.5±0.1), (0.3±0.2), and (0.2±0.1), respectively; the small
scatter of <0.2dex points to rather homogeneous and short star
formation histories. Overall, these results confirm and extend low-
redshift findings of a mass-downsizing evolution. This work further
strengthens the possibility of selecting pure samples of passive
galaxies to be exploited reliably as cosmic chronometers to place
independent cosmological constraints.
Description:
The data used in this study are drawn from the second data release of
LEGA-C (see Straatman+ 2018, J/ApJS/239/27), a recently completed ESO
Public Spectroscopic Survey targeting ∼3000 Ks-band-selected galaxies
at 0.6≲z≲1 in the COSMOS field. The observations were carried out
with the Visible Multi-Object Spectrograph (VIMOS) on the VLT at
Paranal Observatory. The flux-calibrated spectra span a wavelength
range of 6300<λ<8800Å with a spectral resolution of R∼3500
and a median signal-to-noise ratio (S/N) of ∼15 per pixel (0.6Å).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table4.dat 80 140 *Stellar ages, metallicities [Z/H], and
[α/Fe] for 140 massive and passive galaxies
at z∼0.7
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Note on table4.dat: The work is based on data products from observations
made with ESO Telescopes at the La Silla Paranal Observatory under
program ID 194.AF2005(A-N). See also: van der Wel+ (2016ApJS..223...29V 2016ApJS..223...29V)
and Straatman+ (2018, J/ApJS/239/27).
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See also:
J/ApJS/82/197 : Mean UV Spectra of Stellar Groups (Fanelli+ 1992)
J/ApJS/94/687 : Old stellar populations. V. (Worthey+, 1994)
J/ApJS/111/377 : Hγ & Hδ absorption features (Worthey+ 1997)
J/ApJS/116/1 : Old Stellar Populations. VI. Absorption-Line (Trager+ 1998)
J/ApJS/122/51 : Sp. catalog of 10 rich galaxy clusters (Dressler+ 1999)
J/A+A/345/419 : Star formation in early-type galaxies (Longhetti+ 1999)
J/MNRAS/326/959 : Empirical calibration of the NIR Ca triplet (Cenarro+ 2001)
J/ApJ/621/673 : Line indices for 124 early-type galaxies (Thomas+, 2005)
J/ApJ/633/174 : Spheroidals and bulge dominated galaxies (Treu+, 2005)
J/MNRAS/371/703 : MILES library of empirical spectra (Sanchez-Blazquez+, 2006)
J/ApJ/690/1236 : COSMOS photometric redshift catalog (Ilbert+, 2009)
J/AJ/145/77 : Imaging and sp. in 3 galaxy clusters (Jorgensen+, 2013)
J/ApJ/777/18 : Stellar mass functions of galaxies to z=4 (Muzzin+, 2013)
J/ApJS/206/8 : COSMOS/UltraVISTA Ks-selected catalogs v4.1 (Muzzin+, 2013)
J/ApJ/788/72 : Observed sample of z∼0.7 massive galaxies (Gallazzi+, 2014)
J/MNRAS/448/3484 : ATLAS3D Project. XXX (McDermid+, 2015)
J/ApJS/224/24 : The COSMOS2015 catalog (Laigle+, 2016)
J/ApJS/239/27 : LEGA-C DR2: galaxies in the COSMOS field (Straatman+, 2018)
J/MNRAS/490/417 : VANDELS massive quiescent gal. at 1.0<z<1.3 (Carnall+, 2019)
Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- [MMS2013] [26438/259363] Object identifier
(Muzzin+ 2013, J/ApJS/206/8)
8- 16 F9.5 deg RAdeg [149.7/150.8] Right Ascension (J2000)
18- 24 F7.5 deg DEdeg [1.7/2.8] Declination (J2000)
26- 30 F5.3 Gyr Age [1.2/6.1] Mean stellar age
(single-burst star formation history) (1)
32- 36 F5.3 Gyr e16-Age [0.05/1.1] 16th percentile uncertainty in Age
38- 42 F5.3 Gyr e84-Age [0.05/1.4] 84th percentile uncertainty in Age
44- 49 F6.3 [-] [Z/H] [-0.24/0.6] Mean stellar metallicity [Z/H] (1)
51- 55 F5.3 [-] e16-[Z/H] [0.01/0.15] 16th percentile uncertainty in [Z/H]
57- 61 F5.3 [-] e84-[Z/H] [0.01/0.2] 84th percentile uncertainty in [Z/H]
63- 68 F6.3 [-] [a/Fe] [-0.2/0.42] Mean stellar alpha-to-iron (1)
70- 74 F5.3 [-] e16-[a/Fe] [0.007/0.11] 16th percentile uncertainty in
[a/Fe]
76- 80 F5.3 [-] e84-[a/Fe] [0.009/0.12] 84th percentile uncertainty in
[a/Fe]
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Note (1): Stellar population properties age, [Z/H], [a/Fe] were derived
comparing an optimized set of observed Lick indices with Thomas,
Maraston & Johannson (2011MNRAS.412.2183T 2011MNRAS.412.2183T) simple stellar population
models.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 17-Jan-2024