J/ApJ/679/156 Extra central light in galactic nuclei. I. (Hopkins+, 2008)
Dissipation and extra light in galactic nuclei.
I. Gas-rich merger remnants.
Hopkins P.F., Hernquist L., Cox T.J., Dutta S.N., Rothberg B.
<Astrophys. J., 679, 156-181 (2008)>
=2008ApJ...679..156H 2008ApJ...679..156H
ADC_Keywords: Active gal. nuclei ; Morphology ; Magnitudes, absolute
Keywords: cosmology: theory - galaxies: active - galaxies: evolution -
galaxies: nuclei - quasars: general
Abstract:
We study the origin and properties of "extra" or "excess" central
light in the surface brightness profiles of remnants of gas-rich
mergers. By combining a large set of hydrodynamical simulations with
data on observed mergers that span a broad range of profiles at
various masses and degrees of relaxation, we show how to robustly
separate the physically meaningful extra light (i.e., the stellar
population formed in a compact central starburst during a gas-rich
merger) from the outer profile established by violent relaxation
acting on stars already present in the progenitor galaxies prior to
the final stages of the merger. This separation is sensitive to the
treatment of the profile, and we demonstrate that certain fitting
procedures can yield physically misleading results. We show that our
method reliably recovers the younger starburst population, and examine
how the properties and mass of this component scale with the mass, gas
content, and other aspects of the progenitors. We consider the time
evolution of the profiles in different bands, and estimate the biases
introduced by observational studies at different phases and
wavelengths. We show that, when appropriately quantified, extra light
is ubiquitous in both observed and simulated gas-rich merger remnants,
with sufficient mass (∼3%-30% of the stellar mass) to explain the
apparent discrepancy in the maximum phase-space densities of
ellipticals and their progenitor spirals.
Description:
We compare our simulations with the sample of local remnants of recent
gas-rich mergers from Rothberg & Joseph (RJ04, 2004AJ....128.2098R 2004AJ....128.2098R) which
compile K-band imaging, surface brightness, ellipticity, and a4/a
profiles, where the profiles typically range from ∼100pc to ∼10-20kpc.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 91 52 Fits to Rothberg & Joseph (RJ04,
2004AJ....128.2098R 2004AJ....128.2098R) merger remnants
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Source name
12 A1 --- f_Name [078] Source peculiarities (1)
14- 15 I2 h RAh Hour of Right Ascension (J2000)
17- 18 I2 min RAm Minute of Right Ascension (J2000)
20- 21 I2 s RAs Second of Right Ascension (J2000)
23 A1 --- DE- Sign of the Declination (J2000)
24- 25 I2 deg DEd Degree of Declination (J2000)
27- 28 I2 arcmin DEm Arcminute of Declination (J2000)
30- 31 I2 arcsec DEs Arcsecond of Declination (J2000)
33- 38 F6.2 mag KMAG Absolute K band magnitude
40- 42 F3.1 --- nsfit Outer Sersic index of two-component best-fit
profile
44- 46 F3.1 --- nssim Outer Sersic index fit in the same manner to
the best-fit simulations (2)
48- 50 F3.1 --- e_nssim Range in nssim
52- 56 F5.2 --- nsRJ04 Sersic index fit to the entire profile (3)
58- 61 F4.2 --- fe Fraction of light in "extra light"
component of fit
63- 66 F4.2 --- fsb Fraction of light from stars produced in
central, merger-induced starburst (4)
68- 71 F4.2 --- e_fsb Approximate interquartile range in fsb
73- 76 F4.2 --- fgas Initial gas fraction in the best-fitting
simulation (5)
78- 81 F4.2 --- e_fgas Approximate interquartile range in fgas
83- 86 F4.2 --- Dmufit Variance about the fit
88- 91 F4.2 --- Dmusim Variance about the simulation
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Note (1): Flag as follows:
0 = normal object.
7 = AGN contamination affects the central regions (i.e. estimated extra
light) and prevents a good simulation fit (we only model the stellar
profile here).
8 = Unrelaxed or prominent disk/bar features make the comparison with
these objects uncertain.
Note (2): At t∼1-3Gyr after the merger when the system has relaxed.
Note (3): i.e. not decomposed into an outer Sersic and inner extra light
component. Note the authors impose a maximum ns=10.0.
Note (4): Note that this may be biased to high values for actively
star-forming (especially LIRG and ULIRG) systems.
Note (5): This is less robust (note the large interquartile range),
representing a rough gas fraction of the systems ∼a few Gyr before the
final merger, if they evolved in isolation.
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History:
From electronic version of the journal
References:
Hopkins et al. Paper II. 2009ApJS..181..135H 2009ApJS..181..135H.
Hopkins et al. Paper III. 2009ApJS..181..486H 2009ApJS..181..486H.
Hopkins et al. Paper IV. 2009ApJ...691.1424H 2009ApJ...691.1424H.
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 23-Sep-2010