THE IMPRINT OF DISSIPATION ON THE SHAPES OF MERGER REMNANT LOSVDs

Journal Article · Sun Nov 01 04:00:00 EST 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/705/1/920· OSTI ID:21378305

Hoffman, Loren ^[1]; Cox, Thomas J; Dutta, Suvendra; Hernquist, Lars ^[2]

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1. Department of Physics and Astronomy, Northwestern University, Dearborn Observatory, 2131 Tech Drive, Evanston, IL 60208 (United States)
2. Department of Astronomy, Harvard University, 60 Garden Street, Cambridge, MA 02138 (United States)

The properties of elliptical galaxies are broadly consistent with simulated remnants of gas-rich mergers between spirals, motivating more detailed studies of the imprint of this formation mechanism on the remnant distribution function. Gas has a strong impact on the non-Gaussian shapes of the line-of-sight velocity distributions (LOSVDs) of the merger remnant, owing to the embedded disk that forms out of the gas that retains its angular momentum during the merger, and the strong central mass concentration from the gas that falls to the center. The deviations from Gaussianity are effectively parameterized by the Gauss-Hermite moments h {sub 3} and h {sub 4}, which are related to the skewness and kurtosis of the LOSVDs. We quantify the dependence of the (h {sub 3}, h {sub 4})-v/sigma relations on the initial gas fraction f {sub gas} of the progenitor disks in 1:1 mergers, using Gadget-2 simulations including star formation, radiative cooling, and feedback from supernovae and active galactic nuclei. For f {sub gas} approx< 15%, the overall correlation between h {sub 3} and v/sigma is weak, consisting of a flat negatively correlated component arising from edge-on viewing angles plus a steep positively correlated part from more face-on projections. The spread in v/sigma values decreases toward high positive h {sub 4}, and there is a trend toward lower h {sub 4} values as f {sub gas} increases from 0% to 15%. For f {sub gas} approx> 20%, the (h {sub 3}, h {sub 4})-v/sigma distributions look quite different-there is a tight negative h {sub 3}-v/sigma correlation, and a wide spread in v/sigma values at all h {sub 4}, in much better agreement with observations. Re-mergers of the high-f {sub gas} remnants (representing dry mergers) produce slowly rotating systems with near-Gaussian LOSVDs. We explain all of these trends in terms of the underlying orbit structure of the remnants, as molded by their dissipative formation histories.

• OSTI ID: 21378305
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 705; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ANGULAR MOMENTUM
ASYMMETRY
BINARY STARS
COOLING
CORRELATIONS
DISTRIBUTION FUNCTIONS
ERUPTIVE VARIABLE STARS
FEEDBACK
FUNCTIONS
GALAXIES
GALAXY NUCLEI
MATHEMATICS
ORBITS
RADIATIVE COOLING
SIMULATION
STARS
STATISTICS
SUPERNOVAE
VARIABLE STARS