The effects of a hot gaseous halo in galaxy major mergers

Benjamin P. Moster, Andrea Maccio, Rachel S. Somerville, Thorsten Naab, T. J. Cox

Research output: Contribution to journalArticle

Abstract

Cosmological hydrodynamical simulations as well as observations indicate that spiral galaxies comprise five different components: dark matter halo, stellar disc, stellar bulge, gaseous disc and gaseous halo. While the first four components have been extensively considered in numerical simulations of binary galaxy mergers, the effect of a hot gaseous halo has usually been neglected even though it can contain up to 80 per cent of the total gas within the galaxy virial radius. We present a series of hydrodynamic simulations of major mergers of disc galaxies, that for the first time include a diffuse, rotating, hot gaseous halo. Through cooling and accretion, the hot halo can dissipate and refuel the cold gas disc before and after a merger. This cold gas can subsequently form stars, thus impacting the morphology and kinematics of the remnant. Simulations of isolated systems with total mass M~ 1012M show a nearly constant star formation rate of ~5Myr-1 if the hot gaseous halo is included, while the star formation rate declines exponentially if it is neglected. We conduct a detailed study of the star formation efficiency during mergers and find that the presence of a hot gaseous halo reduces the starburst efficiency (e= 0.5) compared to simulations without a hot halo (e= 0.68). The ratio of the peak star formation rate in mergers compared to isolated galaxies is reduced by almost an order of magnitude (from 30 to 5). Moreover, we find cases where the stellar mass of the merger remnant is lower than the sum of the stellar mass of the two progenitor galaxies when evolved in isolation. This suggests a revision to semi-analytic galaxy formation models which assume that a merger always leads to enhanced star formation. In addition, the bulge-to-total ratio after a major merger is decreased if hot gas is included in the halo, due to the formation of a more massive stellar disc in the remnant. We show that adding the hot gas component has a significant effect on the kinematics and internal structure of the merger remnants, like an increased abundance of fast rotators and an r1/4 surface brightness profile at small scales. The consequences on the population of elliptical galaxies formed by disc mergers are discussed.

Original languageEnglish (US)
Pages (from-to)3750-3770
Number of pages21
JournalMonthly Notices of the Royal Astronomical Society
Volume415
Issue number4
DOIs
StatePublished - Aug 1 2011

Fingerprint

merger
halos
galaxies
star formation rate
cold gas
gas
high temperature gases
stellar mass
simulation
star formation
kinematics
effect
disk galaxies
elliptical galaxies
galactic evolution
spiral galaxies
dark matter
isolation
brightness
hydrodynamics

Keywords

  • Galaxies: elliptical and lenticular, cD
  • Galaxies: haloes
  • Galaxies: interactions
  • Galaxies: starburst
  • Galaxies: structure
  • Methods: numerical

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

The effects of a hot gaseous halo in galaxy major mergers. / Moster, Benjamin P.; Maccio, Andrea; Somerville, Rachel S.; Naab, Thorsten; Cox, T. J.

In: Monthly Notices of the Royal Astronomical Society, Vol. 415, No. 4, 01.08.2011, p. 3750-3770.

Research output: Contribution to journalArticle

Moster, Benjamin P. ; Maccio, Andrea ; Somerville, Rachel S. ; Naab, Thorsten ; Cox, T. J. / The effects of a hot gaseous halo in galaxy major mergers. In: Monthly Notices of the Royal Astronomical Society. 2011 ; Vol. 415, No. 4. pp. 3750-3770.
@article{622e9b06fc984e13ba1a7be17a261229,
title = "The effects of a hot gaseous halo in galaxy major mergers",
abstract = "Cosmological hydrodynamical simulations as well as observations indicate that spiral galaxies comprise five different components: dark matter halo, stellar disc, stellar bulge, gaseous disc and gaseous halo. While the first four components have been extensively considered in numerical simulations of binary galaxy mergers, the effect of a hot gaseous halo has usually been neglected even though it can contain up to 80 per cent of the total gas within the galaxy virial radius. We present a series of hydrodynamic simulations of major mergers of disc galaxies, that for the first time include a diffuse, rotating, hot gaseous halo. Through cooling and accretion, the hot halo can dissipate and refuel the cold gas disc before and after a merger. This cold gas can subsequently form stars, thus impacting the morphology and kinematics of the remnant. Simulations of isolated systems with total mass M~ 1012M⊙ show a nearly constant star formation rate of ~5M⊙yr-1 if the hot gaseous halo is included, while the star formation rate declines exponentially if it is neglected. We conduct a detailed study of the star formation efficiency during mergers and find that the presence of a hot gaseous halo reduces the starburst efficiency (e= 0.5) compared to simulations without a hot halo (e= 0.68). The ratio of the peak star formation rate in mergers compared to isolated galaxies is reduced by almost an order of magnitude (from 30 to 5). Moreover, we find cases where the stellar mass of the merger remnant is lower than the sum of the stellar mass of the two progenitor galaxies when evolved in isolation. This suggests a revision to semi-analytic galaxy formation models which assume that a merger always leads to enhanced star formation. In addition, the bulge-to-total ratio after a major merger is decreased if hot gas is included in the halo, due to the formation of a more massive stellar disc in the remnant. We show that adding the hot gas component has a significant effect on the kinematics and internal structure of the merger remnants, like an increased abundance of fast rotators and an r1/4 surface brightness profile at small scales. The consequences on the population of elliptical galaxies formed by disc mergers are discussed.",
keywords = "Galaxies: elliptical and lenticular, cD, Galaxies: haloes, Galaxies: interactions, Galaxies: starburst, Galaxies: structure, Methods: numerical",
author = "Moster, {Benjamin P.} and Andrea Maccio and Somerville, {Rachel S.} and Thorsten Naab and Cox, {T. J.}",
year = "2011",
month = "8",
day = "1",
doi = "10.1111/j.1365-2966.2011.18984.x",
language = "English (US)",
volume = "415",
pages = "3750--3770",
journal = "Monthly Notices of the Royal Astronomical Society",
issn = "0035-8711",
publisher = "Oxford University Press",
number = "4",

}

TY - JOUR

T1 - The effects of a hot gaseous halo in galaxy major mergers

AU - Moster, Benjamin P.

AU - Maccio, Andrea

AU - Somerville, Rachel S.

AU - Naab, Thorsten

AU - Cox, T. J.

PY - 2011/8/1

Y1 - 2011/8/1

N2 - Cosmological hydrodynamical simulations as well as observations indicate that spiral galaxies comprise five different components: dark matter halo, stellar disc, stellar bulge, gaseous disc and gaseous halo. While the first four components have been extensively considered in numerical simulations of binary galaxy mergers, the effect of a hot gaseous halo has usually been neglected even though it can contain up to 80 per cent of the total gas within the galaxy virial radius. We present a series of hydrodynamic simulations of major mergers of disc galaxies, that for the first time include a diffuse, rotating, hot gaseous halo. Through cooling and accretion, the hot halo can dissipate and refuel the cold gas disc before and after a merger. This cold gas can subsequently form stars, thus impacting the morphology and kinematics of the remnant. Simulations of isolated systems with total mass M~ 1012M⊙ show a nearly constant star formation rate of ~5M⊙yr-1 if the hot gaseous halo is included, while the star formation rate declines exponentially if it is neglected. We conduct a detailed study of the star formation efficiency during mergers and find that the presence of a hot gaseous halo reduces the starburst efficiency (e= 0.5) compared to simulations without a hot halo (e= 0.68). The ratio of the peak star formation rate in mergers compared to isolated galaxies is reduced by almost an order of magnitude (from 30 to 5). Moreover, we find cases where the stellar mass of the merger remnant is lower than the sum of the stellar mass of the two progenitor galaxies when evolved in isolation. This suggests a revision to semi-analytic galaxy formation models which assume that a merger always leads to enhanced star formation. In addition, the bulge-to-total ratio after a major merger is decreased if hot gas is included in the halo, due to the formation of a more massive stellar disc in the remnant. We show that adding the hot gas component has a significant effect on the kinematics and internal structure of the merger remnants, like an increased abundance of fast rotators and an r1/4 surface brightness profile at small scales. The consequences on the population of elliptical galaxies formed by disc mergers are discussed.

AB - Cosmological hydrodynamical simulations as well as observations indicate that spiral galaxies comprise five different components: dark matter halo, stellar disc, stellar bulge, gaseous disc and gaseous halo. While the first four components have been extensively considered in numerical simulations of binary galaxy mergers, the effect of a hot gaseous halo has usually been neglected even though it can contain up to 80 per cent of the total gas within the galaxy virial radius. We present a series of hydrodynamic simulations of major mergers of disc galaxies, that for the first time include a diffuse, rotating, hot gaseous halo. Through cooling and accretion, the hot halo can dissipate and refuel the cold gas disc before and after a merger. This cold gas can subsequently form stars, thus impacting the morphology and kinematics of the remnant. Simulations of isolated systems with total mass M~ 1012M⊙ show a nearly constant star formation rate of ~5M⊙yr-1 if the hot gaseous halo is included, while the star formation rate declines exponentially if it is neglected. We conduct a detailed study of the star formation efficiency during mergers and find that the presence of a hot gaseous halo reduces the starburst efficiency (e= 0.5) compared to simulations without a hot halo (e= 0.68). The ratio of the peak star formation rate in mergers compared to isolated galaxies is reduced by almost an order of magnitude (from 30 to 5). Moreover, we find cases where the stellar mass of the merger remnant is lower than the sum of the stellar mass of the two progenitor galaxies when evolved in isolation. This suggests a revision to semi-analytic galaxy formation models which assume that a merger always leads to enhanced star formation. In addition, the bulge-to-total ratio after a major merger is decreased if hot gas is included in the halo, due to the formation of a more massive stellar disc in the remnant. We show that adding the hot gas component has a significant effect on the kinematics and internal structure of the merger remnants, like an increased abundance of fast rotators and an r1/4 surface brightness profile at small scales. The consequences on the population of elliptical galaxies formed by disc mergers are discussed.

KW - Galaxies: elliptical and lenticular, cD

KW - Galaxies: haloes

KW - Galaxies: interactions

KW - Galaxies: starburst

KW - Galaxies: structure

KW - Methods: numerical

UR - http://www.scopus.com/inward/record.url?scp=80051809571&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=80051809571&partnerID=8YFLogxK

U2 - 10.1111/j.1365-2966.2011.18984.x

DO - 10.1111/j.1365-2966.2011.18984.x

M3 - Article

VL - 415

SP - 3750

EP - 3770

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 4

ER -