J/ApJ/786/L10 Stellar IMF mass normalization for z∼1 galaxies (Shetty+, 2014)
Salpeter normalization of the stellar initial mass function for massive galaxies
at z∼1.
Shetty S., Cappellari M.
<Astrophys. J., 786, L10 (2014)>
=2014ApJ...786L..10S 2014ApJ...786L..10S (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, photometry ; Models ; Redshifts ; Velocity dispersion
Keywords: galaxies: evolution - galaxies: formation - galaxies: high-redshift -
galaxies: kinematics and dynamics - galaxies: structure
Abstract:
The stellar initial mass function (IMF) is a key parameter for
studying galaxy evolution. Here we measure the IMF mass normalization
for a sample of 68 field galaxies in the redshift range 0.7-0.9 within
the Extended Groth Strip. To do this we derive the total (stellar +
dark matter) mass-to-light [(M/L)] ratio using axisymmetric dynamical
models. Within the region where we have kinematics (about one
half-light radius), the models assume (1) that mass follows light,
implying negligible differences between the slope of the stellar and
total density profiles, (2) constant velocity anisotropy
(βz=1-σz2/σR2=0.2), and (3) that galaxies are
seen at the average inclination for random orientations (i.e., i=60°,
where i=90° represents edge-on). The dynamical models are based
on anisotropic Jeans equations, constrained by Hubble Space
Telescope/Advanced Camera for Surveys imaging and the central velocity
dispersion of the galaxies, extracted from good-quality spectra taken
by the DEEP2 survey. The population (M/L) are derived from full-spectrum
fitting of the same spectra with a grid of simple stellar population
models. Recent dynamical modeling results from the ATLAS3D project
and numerical simulations of galaxy evolution indicate that the dark
matter fraction within the central regions of our galaxies should be
small. This suggests that our derived total (M/L) should closely
approximate the stellar M/L. Our comparison of the dynamical (M/L) and
the population (M/L) then implies that for galaxies with stellar mass
M*≳1011 M☉, the average normalization of the IMF is
consistent with a Salpeter slope, with a substantial scatter. This is
similar to what is found within a similar mass range for nearby galaxies.
Description:
The one-dimensional (1D) spectrum of our galaxies was obtained from
the DEEP2 spectrographic survey (Newman et al. 2013ApJS..208....5N 2013ApJS..208....5N).
It is a magnitude-limited, RAB≤24.1, galaxy redshift survey. In
this study, we use the Extended Groth Strip (EGS; Groth et al.
1994BAAS...26.1403W 1994BAAS...26.1403W) field of the survey due to the availability of
Hubble Space Telescope (HST) imaging (Davis et al. 2007ApJ...660L...1D 2007ApJ...660L...1D).
The data was taken by the DEIMOS multi-object spectrograph, mounted on
the Keck-2 Telescope, with a observed wavelength range of 6500-9100 Å,
in a spectral resolution of R∼6000 at 7800 Å. The typical total
exposure time for each galaxy is 1 hr, with average seeing of 0.85".
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 44 68 Results of dynamical models and multiple
population fitting
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See also:
II/301 : The DEEP2-DR1 Photometric Catalog (Coil+ 2004)
J/ApJ/625/6 : Galaxy groups in the DEEP2 Galaxy Redshift Survey (Gerke+, 2005)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 I8 --- ID DEEP2 identifier (DEEP2-GRS NNNNNNNN
in Simbad)
10- 14 F5.3 --- z DEEP2 estimated redshift
16- 21 F6.2 mag BMag Absolute B-band Vega magnitude (1)
23- 26 F4.2 arcsec Reff Effective radius (2)
28- 30 I3 km/s sigma Aperture velocity dispersion
32- 33 I2 km/s e_sigma Error in sigma
35- 39 F5.2 Msun/Lsun (M/L)JAM Jeans Anisotropic multi-Gaussian expansion
(JAM) dynamical mass-to-light ratio (3)
41- 44 F4.2 Msun/Lsun (M/L)Sal Salpeter population mass-to-light ratio (4)
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Note (1): Derived using multi-Gaussian expansion (MGE).
Note (2): As derived from multi-Gaussian expansion (MGE) (without re-scaling).
Note (3): With a median error of 0.11dex.
Note (4): With a scatter of 0.08dex.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 20-Jun-2017