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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 (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-σz2R2=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). 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) field of the survey due to the availability of Hubble Space Telescope (HST) imaging (Davis et al. 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:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 44 68 Results of dynamical models and multiple population fitting
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
Bytes Format Units Label Explanations
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)
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.
History: From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 20-Jun-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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