J/A+A/438/507 Degree of lopsidedness for galaxies (Bournaud+, 2005)
Lopsided spiral galaxies: evidence for gas accretion.
Bournaud F., Combes F., Jog C.J., Puerari I.
<Astron. Astrophys., 438, 507-520 (2005)>
=2005A&A...438..507B 2005A&A...438..507B
ADC_Keywords: Galaxies, IR ; Morphology
Keywords: galaxies: evolution - galaxies: formation - galaxies: structure -
galaxies: spiral
Abstract:
We quantify the degree of lopsidedness for a sample of 149 galaxies
observed in the near-infrared from the Ohio State University Bright
Galaxy Survey (OSUBGS, Eskridge et al. 2002, Cat. J/ApJS/143/73)
sample, and try to explain the physical origin of the observed disk
lopsidedness. We confirm previous studies, but for a larger sample,
that a large fraction of galaxies have significant lopsidedness in
their stellar disks, measured as the Fourier amplitude of the m=1
component normalised to the average or m=0 component in the surface
density. Late-type galaxies are found to be more lopsided, while the
presence of m=2 spiral arms and bars is correlated with disk
lopsidedness. We also show that the m=1 amplitude is uncorrelated with
the presence of companions. Numerical simulations were carried out to
study the generation of m=1 via different processes: galaxy tidal
encounters, galaxy mergers, and external gas accretion with subsequent
star formation. These simulations show that galaxy interactions and
mergers can trigger strong lopsidedness, but do not explain several
independent statistical properties of observed galaxies. To explain
all the observational results, it is required that a large fraction of
lopsidedness results from cosmological accretion of gas on galactic
disks, which can create strongly lopsided disks when this accretion is
asymmetrical enough.
Description:
To quantify the amplitude of the m=1 mode both in the disk surface
density and in the potential, we use near-infrared images from the
Ohio State University Bright Galaxy Survey (OSUBGS, Eskridge et al.
2002, Cat. J/ApJS/143/73).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 32 171 Inclination and values of and for
galaxies in our sample
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See also:
J/ApJS/143/73 : OSUBGS, Morphology of spiral galaxies (Eskridge+, 2002)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- Name Galaxy name
12- 16 F5.2 deg incl Inclination
20- 24 F5.3 --- m=1 asymmetry in the OSUBGS sample (1)
28- 32 F5.3 --- m=2 asymmetry in the OSUBGS sample (1)
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Note (1): Ohio State University Bright Galaxy Survey, Cat. J/ApJS/143/73
The m-valu corresponds to the number of arm pairs.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 28-Dec-2006