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EVIDENCE FOR A CONSTANT INITIAL MASS FUNCTION IN EARLY-TYPE GALAXIES BASED ON THEIR X-RAY BINARY POPULATIONS
- Source :
- Peacock, M B, Zepf, S E, Maccarone, T J, Kundu, A, Gonzalez, A H, Lehmer, B D & Maraston, C 2014, ' Evidence for a constant initial mass function in early-type galaxies based on their X-ray binary populations ', The Astrophysical Journal, vol. 784, no. 2, pp. 1-11 . https://doi.org/10.1088/0004-637X/784/2/162
- Publication Year :
- 2014
- Publisher :
- American Astronomical Society, 2014.
-
Abstract
- A number of recent studies have proposed that the stellar initial mass function (IMF) of early type galaxies varies systematically as a function of galaxy mass, with higher mass galaxies having bottom heavy IMFs. These bottom heavy IMFs have more low-mass stars relative to the number of high mass stars, and therefore naturally result in proportionally fewer neutron stars and black holes. In this paper, we specifically predict the variation in the number of black holes and neutron stars based on the power-law IMF variation required to reproduce the observed mass-to-light ratio trends with galaxy mass. We then test whether such variations are observed by studying the field low-mass X-ray binary populations (LMXBs) of nearby early-type galaxies. In these binaries, a neutron star or black hole accretes matter from a low-mass donor star. Their number is therefore expected to scale with the number of black holes and neutron stars present in a galaxy. We find that the number of LMXBs per K-band light is similar among the galaxies in our sample. These data therefore demonstrate the uniformity of the slope of the IMF from massive stars down to those now dominating the K-band light, and are consistent with an invariant IMF. Our results are inconsistent with an IMF which varies from a Kroupa/Chabrier like IMF for low mass galaxies to a steep power-law IMF (with slope $x$=2.8) for high mass galaxies. We discuss how these observations constrain the possible forms of the IMF variations and how future Chandra observations can enable sharper tests of the IMF.
- Subjects :
- Physics
Initial mass function
Astrophysics::High Energy Astrophysical Phenomena
X-ray binary
Binary number
Astronomy and Astrophysics
Astrophysics::Cosmology and Extragalactic Astrophysics
Astrophysics
stellar content [galaxies]
Galaxy
Black hole
Neutron star
Stars
luminosity function [stars]
mass function
Space and Planetary Science
binaries [X-rays]
Low Mass
elliptical and lenticular, cD [galaxies]
Astrophysics::Galaxy Astrophysics
Subjects
Details
- ISSN :
- 15384357 and 0004637X
- Volume :
- 784
- Database :
- OpenAIRE
- Journal :
- The Astrophysical Journal
- Accession number :
- edsair.doi.dedup.....37c68744f92cd45c14fa90fddb00e0a7