J/ApJ/733/74 GALEX - SDSS properties of local galaxies (Lemonias+, 2011)
The space density of extended ultraviolet (XUV) disks in the local universe and
implications for gas accretion onto galaxies.
Lemonias J.J., Schiminovich D., Thilker D., Wyder T.K., Martin D.C.,
Seibert M., Treyer M.A., Bianchi L., Heckman T.M., Madore B.F., Rich R.M.
<Astrophys. J., 733, 74 (2011)>
=2011ApJ...733...74L 2011ApJ...733...74L
ADC_Keywords: Galaxies, nearby ; Photometry, SDSS ; Photometry, ultraviolet
Keywords: galaxies: evolution - galaxies: formation - galaxies: structure -
surveys - ultraviolet: galaxies
Abstract:
We present results of the first unbiased search for extended
ultraviolet (XUV)-disk galaxies undertaken to determine the space
density of such galaxies. Our sample contains 561 local (0.001<z<0.05)
galaxies that lie in the intersection of available Galaxy Evolution
Explorer (GALEX) deep imaging (exposure time >1.5x104s) and Sloan
Digital Sky Survey DR7 footprints. We explore modifications to the
standard classification scheme for our sample that includes both disk-
and bulge-dominated galaxies. Visual classification of each galaxy in
the sample reveals an XUV-disk frequency of up to 20% for the most
nearby portion of our sample. On average over the entire sample (out
to z=0.05) the frequency ranges from a hard limit of 4%-14%. The GALEX
imaging allows us to detect XUV disks beyond 100 Mpc. The XUV regions
around XUV-disk galaxies are consistently bluer than the main bodies.
We find a surprisingly high frequency of XUV emission around luminous
red (NUV-r>5) and green valley (3<NUV-r<5) galaxies. The XUV-disk
space density in the local universe is >(1.5-4.2)x10-3Mpc-3. Using
the XUV emission as an indicator of recent gas accretion, we estimate
that the cold gas accretion rate onto these galaxies is
>(1.7-4.6)x10-3M☉/Mpc3/yr. The number of XUV disks in the
green valley and the estimated accretion rate onto such galaxies
points to the intriguing possibility that 7%-18% of galaxies in this
population are transitioning away from the red sequence.
Description:
Observations of each object were obtained from GALEX deep imaging
collected as part of primary mission surveys. All objects were imaged
by GALEX in the near-UV (NUV; 1750-2750Å) and far-UV (FUV;
1350-1750Å) bands.
Cut-outs of the SDSS r-band FITS images and SDSS gri color composite
images of each GALEX-SDSS matched object were generated using smosaic.
Optical measurements (Petrosian magnitudes, R50, R90, and Galactic
reddening) as well as stellar mass for each object were obtained from
the MPA-JHU SDSS catalogs.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 95 561 Properties of sample galaxies
table2.dat 41 80 Properties of XUV-disks and XUV-ambiguous galaxies
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See also:
J/A+A/544/A65 : GALEX Arecibo SDSS survey. VI. (Catinella+, 2012)
J/ApJ/741/79 : The Spitzer-SDSS-GALEX Spectroscopic Survey (O'Dowd+, 2011)
J/ApJ/731/28 : UV star-forming association in galaxies (Alberts+, 2011)
J/AJ/140/1194 : FUV/HI relations in nearby galaxies (Bigiel+, 2010)
J/AJ/140/1975 : Normal galaxies optical and UV photometry (Smith+, 2010)
J/MNRAS/403/683 : GALEX Arecibo SDSS survey (GASS) (Catinella+, 2010)
J/ApJS/173/538 : XUV-Disk galaxies in the Local Universe (Thilker+, 2007)
J/ApJS/173/293 : UV-Optical galaxy color-magnitude diagram I. (Wyder+, 2007)
J/A+AS/114/527 : UV properties of normal galaxies. III. (Rifatto+, 1995)
http://www.sdss.org/ : SDSS home page
http://galex.stsci.edu/GR6/ : GALEX GR6 archive
http://www.mpa-garching.mpg.de/SDSS/DR7/ : The MPA-JHU DR7 of spectrum web page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [SDSS]
6- 24 A19 --- SDSS SDSS name (JHHMMSS.ss+DDMMSS.s)
26- 33 F8.4 deg RAdeg Right Ascension in decimal degrees (J2000)
34 A1 --- --- [0]
36- 42 F7.4 deg DEdeg Declination in decimal degrees (J2000)
43 A1 --- --- [0]
45- 49 F5.3 --- z [0.003/0.05] Redshift
50 A1 --- --- [0]
52- 56 F5.1 ks NUVexp NUV exposure time
57 A1 --- --- [0]
59- 63 F5.1 ks FUVexp FUV exposure time
64 A1 --- --- [0]
66- 69 F4.2 mag NUV-r [0.04/6.42] The (NUV-r) color index
70 A1 --- --- [0]
72- 75 F4.2 mag FUV-r [0.55/8.7] The (FUV-r) color index
76 A1 --- --- [0]
78- 82 F5.2 mag rmag [12.17/18.51] SDSS r band magnitude
83 A1 --- --- [0]
85- 89 F5.2 [Msun] logM* [8/11.54] Log of the mass
90 A1 --- --- [0]
92- 95 F4.2 --- C Concentration index; C=R90/R50
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [SDSS]
6- 24 A19 --- SDSS SDSS name (JHHMMSS.ss+DDMMSS.s)
26- 31 F6.3 mag FUV-r(XUV) The (FUV-r) color of XUV region
33- 37 F5.2 --- R80/RXUV [0.1/26] The R80/RXUV ratio (1)
39 A1 --- Type [AD] Source type; D=XUV-disk, A=XUV-amb.
41 A1 --- Rej? [NY] Reject; Y=Reject, N=Non-reject
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Note (1): In order to assess why a fraction of XUV disks and XUV-ambiguous
galaxies have remarkably red XUV regions, we found the contour that
includes 80% of the r-band light, R80. We define R80 as the mean
of the projected major and minor axes of this contour. RXUV is the
extent of the XUV threshold (also measured in projection). See section
4.4.2 and Figure 13 for further details.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 09-Nov-2012