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Title: AN INVENTORY OF THE STELLAR INITIAL MASS FUNCTION IN EARLY-TYPE GALAXIES

Abstract

Given a flurry of recent claims for systematic variations in the stellar initial mass function (IMF), we carry out the first inventory of the observational evidence using different approaches. This includes literature results, as well as our own new findings from combined stellar population synthesis (SPS) and Jeans dynamical analyses of data on {approx}4500 early-type galaxies (ETGs) from the SPIDER project. We focus on the mass-to-light ratio mismatch relative to the Milky Way IMF, {delta}{sub IMF}, correlated against the central stellar velocity dispersion, {sigma}{sub *}. We find a strong correlation between {delta}{sub IMF} and {sigma}{sub *}, for a wide set of dark matter (DM) model profiles. These results are robust if a uniform halo response to baryons is adopted across the sample. The overall normalization of {delta}{sub IMF} and the detailed DM profile are less certain, but the data are consistent with standard cold DM halos and a central DM fraction that is roughly constant with {sigma}{sub *}. For a variety of related studies in the literature, using SPS, dynamics, and gravitational lensing, similar results are found. Studies based solely on spectroscopic line diagnostics agree on a Salpeter-like IMF at high {sigma}{sub *} but differ at low {sigma}{sub *}. Overall,more » we find that multiple independent lines of evidence appear to be converging on a systematic variation in the IMF, such that high-{sigma}{sub *} ETGs have an excess of low-mass stars relative to spirals and low-{sigma}{sub *} ETGs. Robust verification of super-Salpeter IMFs in the highest-{sigma}{sub *} galaxies will require additional scrutiny of scatter and systematic uncertainties. The implications for the distribution of DM are still inconclusive.« less

Authors:
 [1];  [2];  [3]
  1. Institut fuer Theoretische Physik, Universitaet Zuerich, Winterthurerstrasse 190, CH-8057 Zuerich (Switzerland)
  2. University of California Observatories, 1156 High Street, Santa Cruz, CA 95064 (United States)
  3. INAF-Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, I-80131 Napoli (Italy)
Publication Date:
OSTI Identifier:
22167667
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 765; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTRONOMY; ASTROPHYSICS; BARYONS; CORRELATIONS; GALACTIC EVOLUTION; GRAVITATIONAL LENSES; MASS; MILKY WAY; NONLUMINOUS MATTER; STAR EVOLUTION; STARS; SYNTHESIS; VARIATIONS; VISIBLE RADIATION

Citation Formats

Tortora, C., Romanowsky, A. J., and Napolitano, N. R., E-mail: ctortora@physik.uzh.ch. AN INVENTORY OF THE STELLAR INITIAL MASS FUNCTION IN EARLY-TYPE GALAXIES. United States: N. p., 2013. Web. doi:10.1088/0004-637X/765/1/8.
Tortora, C., Romanowsky, A. J., & Napolitano, N. R., E-mail: ctortora@physik.uzh.ch. AN INVENTORY OF THE STELLAR INITIAL MASS FUNCTION IN EARLY-TYPE GALAXIES. United States. doi:10.1088/0004-637X/765/1/8.
Tortora, C., Romanowsky, A. J., and Napolitano, N. R., E-mail: ctortora@physik.uzh.ch. Fri . "AN INVENTORY OF THE STELLAR INITIAL MASS FUNCTION IN EARLY-TYPE GALAXIES". United States. doi:10.1088/0004-637X/765/1/8.
@article{osti_22167667,
title = {AN INVENTORY OF THE STELLAR INITIAL MASS FUNCTION IN EARLY-TYPE GALAXIES},
author = {Tortora, C. and Romanowsky, A. J. and Napolitano, N. R., E-mail: ctortora@physik.uzh.ch},
abstractNote = {Given a flurry of recent claims for systematic variations in the stellar initial mass function (IMF), we carry out the first inventory of the observational evidence using different approaches. This includes literature results, as well as our own new findings from combined stellar population synthesis (SPS) and Jeans dynamical analyses of data on {approx}4500 early-type galaxies (ETGs) from the SPIDER project. We focus on the mass-to-light ratio mismatch relative to the Milky Way IMF, {delta}{sub IMF}, correlated against the central stellar velocity dispersion, {sigma}{sub *}. We find a strong correlation between {delta}{sub IMF} and {sigma}{sub *}, for a wide set of dark matter (DM) model profiles. These results are robust if a uniform halo response to baryons is adopted across the sample. The overall normalization of {delta}{sub IMF} and the detailed DM profile are less certain, but the data are consistent with standard cold DM halos and a central DM fraction that is roughly constant with {sigma}{sub *}. For a variety of related studies in the literature, using SPS, dynamics, and gravitational lensing, similar results are found. Studies based solely on spectroscopic line diagnostics agree on a Salpeter-like IMF at high {sigma}{sub *} but differ at low {sigma}{sub *}. Overall, we find that multiple independent lines of evidence appear to be converging on a systematic variation in the IMF, such that high-{sigma}{sub *} ETGs have an excess of low-mass stars relative to spirals and low-{sigma}{sub *} ETGs. Robust verification of super-Salpeter IMFs in the highest-{sigma}{sub *} galaxies will require additional scrutiny of scatter and systematic uncertainties. The implications for the distribution of DM are still inconclusive.},
doi = {10.1088/0004-637X/765/1/8},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 765,
place = {United States},
year = {2013},
month = {3}
}