J/MNRAS/469/3363 Offset discs and bars in SDSS galaxies (Kruk+, 2017)
Galaxy Zoo: finding offset discs and bars in SDSS galaxies.
Kruk S.J., Lintott C.J., Simmons B.D., Bamford S.P., Cardamone C.N.,
Fortson L., Hart R.E., Haussler B., Masters K.L., Nichol R.C.,
Schawinski K., Smethurst R.J.
<Mon. Not. R. Astron. Soc., 469, 3363-3373 (2017)>
=2017MNRAS.469.3363K 2017MNRAS.469.3363K (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies ; Morphology
Keywords: galaxies: dwarf - galaxies: evolution - galaxies: interactions -
galaxies: irregular - galaxies: structure
Abstract:
We use multiwavelength Sloan Digital Sky Survey (SDSS) images and
Galaxy Zoo morphologies to identify a sample of ∼270 late-type
galaxies with an off-centre bar. We measure offsets in the range
0.2-2.5kpc between the photometric centres of the stellar disc and
stellar bar. The measured offsets correlate with global asymmetries of
the galaxies, with those with largest offsets showing higher
lopsidedness. These findings are in good agreement with predictions
from simulations of dwarf-dwarf tidal interactions producing
off-centre bars. We find that the majority of galaxies with off-centre
bars are of Magellanic type, with a median mass of 109.6M☉,
and 91 per cent of them having M*<3x1010M☉, the characteristic
mass at which galaxies start having higher central concentrations
attributed to the presence of bulges. We conduct a search for
companions to test the hypothesis of tidal interactions, but find that
a similar fraction of galaxies with offset bars have companions within
100kpc as galaxies with centred bars. Although this may be due to the
incompleteness of the SDSS spectroscopic survey at the faint end,
alternative scenarios that give rise to offset bars such as
interactions with dark companions or the effect of lopsided halo
potentials should be considered. Future observations are needed to
confirm possible low-mass companion candidates and to determine the
shape of the dark matter halo, in order to find the explanation for
the off-centre bars in these galaxies.
Description:
All the galaxies used in the study are drawn from the SDSS DR7
(Strauss et al. 2002AJ....124.1810S 2002AJ....124.1810S; Abazajian et al.
2009ApJS..182..543A 2009ApJS..182..543A). We use visual classifications of galaxy
morphologies from the Galaxy Zoo 21 project (GZ2; Willett et al.,
2013, Cat. J/MNRAS/435/2835), which asked citizen scientists to
provide detailed information about the visual appearance of galaxies.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 84 271 Properties of the 271 galaxies in the offset sample,
fitted with disc+bar or disc+bar+bulge components
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See also:
J/ApJ/711/284 : Galaxy Zoo: AGN host galaxies (Schawinski+, 2010)
J/MNRAS/396/818 : Blue early-type galaxies in Galaxy Zoo (Schawinski+, 2009)
J/MNRAS/405/783 : Passive red spirals in Galaxy Zoo (Masters+, 2010)
J/MNRAS/410/166 : Morphological types from Galaxy Zoo 1 (Lintott+, 2011)
J/MNRAS/420/1684 : End of red sequence galaxies in Galaxy Zoo (Wong+, 2012)
J/MNRAS/435/2835 : Morphological types from Galaxy Zoo 2 (Willett+, 2013)
J/MNRAS/461/3663 : Galaxy Zoo 2: new classification (Hart+, 2016)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- Name SDSS name (JHHMMSS.ss+DDMMSS.s)
21- 26 F6.4 --- z Redshift (from SDSS DR7)
28- 32 F5.2 mag rmag r-band apparent Petrosian magnitude
(from SDSS DR7)
34- 38 F5.2 kpc ReDisc Disc effective radius
40- 43 F4.2 --- nDisc Disk Sersic index (1)
44- 48 F5.2 kpc ReBar Bar effective radius
50- 53 F4.2 --- nbar Bar Sersic index (1)
55- 58 F4.2 kpc ReBulge Bulge effective radius
60- 63 F4.2 --- nbulge Bulge Sersic index (1)
65- 69 F5.2 [Msun] logMass ?=-1 Average stellar mass (from the MPA-JHU
catalogue (Kauffmann et al.,
2003MNRAS.341...33K 2003MNRAS.341...33K))
71- 74 F4.2 --- A1 Amplitude of the first Fourier mode (m=1) (2)
76- 79 F4.2 arcsec Off1 Offset between the photometric centres of the
disc and of the bar in arcsec
81- 84 F4.2 kpc Off2 Offset between the photometric centres of the
disc and of the bar deprojected using
equation (1) (in kpc)
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Note (1): The disc component was fitted with an exponential profile (n=1),
while the bar and bulge were each fitted with a free Sersic profile.
Note (2): quantifies the lopsidedness of the galaxy disc, the variation in the
size of the effective radius on opposing sides of the galaxy.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 15-Apr-2020