J/MNRAS/444/2571 Early-Type Galaxies in SDSS and GALEX (Hernandez-Perez+, 2014)
Binary stars and the UVX in early-type galaxies.
Hernandez-Perez F., Bruzual G.
<Mon. Not. R. Astron. Soc., 444, 2571-2579 (2014)>
=2014MNRAS.444.2571H 2014MNRAS.444.2571H
ADC_Keywords: Galaxy catalogs ; Ultraviolet ; Photometry, SDSS ;
Spectroscopy
Keywords: stars: horizontal branch - galaxies: elliptical and lenticular -
ultraviolet: galaxies
Abstract:
We use the Hernandez-Perez and Bruzual stellar population synthesis
models to study the role of interacting binary pairs as progenitors of
extreme horizontal branch (EHB) stars. We assemble a sample of 3417
early-type galaxies observed both in the optical (SDSS-DR8) and the UV
(GALEX-GR6). The galaxies in our sample can be classified according to
their position in the colour-colour diagram as UV-weak or red-sequence
galaxies (∼48%), UV-strong or UVX galaxies (∼9%), and recent
star-forming galaxies (∼43%). Analysing this sample using the models
for various choices of basic model parameters, we conclude that (a)
the UVr colours of UV-weak and UV-strong galaxies are reproduced by
the models as long as the fraction of binary stars is at least 15%.
(b) Higher metallicity models (Z=0.02 and 0.03) reproduce the colours
of UV-weak and UV-strong galaxies better than lower Z models. The
Z=0.03 model is slightly bluer than the Z=0.02 model in the UV-strong
region, indicating a weak relationship between UVX and Z. (c) The
strength of UVX increases with age in the model population. This is at
variance with the results of other models that include binary stars as
progenitors of EHB stars.
Description:
To study the UVX phenomenon in ETGs using the Hernandez-Perez &
Bruzual (2013MNRAS.431.2612H 2013MNRAS.431.2612H) models, we must build a sample of
galaxies observed both in the UV and optical ranges. The SDSS and the
GALEX Medium Imaging Survey (GALEX-MIS) overlap over 1000 square
degrees in the sky and contain a considerable number of objects in
common. We use SDSS pipeline parameters to select ETG candidates from
the SDSS-DR8 (Aihara et al., 2011ApJS..193...29A 2011ApJS..193...29A), which will then
matched to their GALEX counterparts.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 362 3417 *Photometric and spectroscopic information of
the 3417 early-type galaxies (ETG) sample
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Note on table2.dat: This catalogue contains UV GALEX and optical SDSS
photometry of ETGs with no signs of nuclear activity and/or important
events of recent star formation.
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See also:
II/312 : GALEX-DR5 (GR5) sources from AIS and MIS (Bianchi+ 2011)
http://skyserver.sdss.org/dr8/en : SDSS DR8 Home Page
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 6 F6.3 mag umag Petrosian u magnitude (petroMag_u)
8- 13 F6.3 mag gmag Petrosian g magnitude (petroMag_g)
15- 20 F6.3 mag imag Petrosian i magnitude (petroMag_i)
22- 30 F9.5 deg RAdeg SDSS right ascension (J2000) (ra_sdss)
32- 40 F9.5 deg DEdeg SDSS declination (J2000) (dec_1)
42- 50 F9.5 deg GLON Galactic longitude (l)
52- 60 F9.5 deg GLAT Galactic latitude (b)
62- 67 F6.3 mag rmag Petrosian r magnitude (petroMag_r)
69- 75 F7.3 mag rMAG Absolute r magnitude (Mr)
77- 83 F7.3 mag iMAG Absolute i magnitude (Mi)
85- 91 F7.3 mag gMAG Absolute g magnitude (Mg)
93- 99 F7.3 mag uMAG Absolute u magnitude (Mu)
101-106 F6.3 [-] NII/Ha [-3.4/2.9]?=- log([NII]/Hα) line ratio
(log10([NII]/Ha)
107 A1 --- f_NII/Ha [I] for Infinity in [NII]/Hα
109-114 F6.3 [-] OIII/Hb [-2.5/1.6]?=- log([OIII]/Hβ) line ratio
(log10([OIII]/Hb))
116-134 I19 --- GALEX GALEX objId (ObjID_GALEX)
136-144 F9.5 deg RAGdeg GALEX right ascension (J2000) (ra_galex)
146-154 F9.5 deg DEGdeg GALEX declination (J2000) (dec_galex)
156-161 F6.3 mag NUV NUV magnitude (nuv_mag)
163-167 F5.3 mag e_NUV rms uncertainty on NUV (nuv_magerr)
169-174 F6.3 mag FUV FUV magnitude (fuv_mag)
176-180 F5.3 mag e_FUV rms uncertainty on FUV (fuv_magerr)
182-187 F6.3 mag NUV-r NUV-r colour index
189-194 F6.3 mag FUV-r FUV-r colour index
196-201 F6.3 mag FUV-NUV FUV-NUV colour index
203-208 F6.3 mag FUV-i FUV-i colour index
210-215 F6.3 mag NUV-i NUV-i colour index
217-235 I19 --- SDSS SDSS objId (objid_SDSS)
237-255 I19 --- SpID SDSS specobjid (specobjid)
257-262 F6.3 mag DM [34.9/39.9] Distance modulus (distMod)
264-270 F7.3 0.1nm REW5007 [-17/1.5] [OIII] 5007 equivalent width
(oiii5007reqw_2) (1)
272-277 F6.3 0.1nm e_REW5007 [0.06/0.6] rms uncertainty on REW5007
279-284 F6.2 10-20W/m2 F5007 [-21/708] [OIII] 5007 flux (10-17erg/cm
(oiii5007flux_2) (2)
286-291 F6.3 0.1nm REW(Hb) [-1/1.8] Hβ equivalent width
(hbetareqw_2) (1)
293-297 F5.3 0.1nm e_REW(Hb) [0.05/0.6] rms uncertainty on REW(Hb)
299-304 F6.1 10-20W/m2 FHb [-2/520] Hβ flux (hbetaflux_2) (2)
306-310 F5.1 10-20W/m2 e_FHb [1/28] rms uncertainty on FHB
312-317 F6.2 0.1nm REW(Ha) [-26/2] Hα equivalent width
(halphareqw_2) (1)
319-323 F5.2 0.1nm e_REW(Ha) [0.05/1.2] rms uncertainty on REW(Ha)
325-330 F6.1 10-20W/m2 FHa [-38/2520] Hα flux (halphaflux_2) (2)
332-336 F5.1 10-20W/m2 e_FHa [-1/59] rms uncertainty on FHA
338-343 F6.2 0.1nm REW6584 [-17/2] [NII] 6584 equivalent width
(nii6584reqw_2) (1)
345-349 F5.2 0.1nm e_REW6584 [0.05/1.1] rms uncertainty on REW6584
351-356 F6.1 10-20W/m2 F6584 [-82/1600] [NII] flux (nii6584flux_2) (2)
358-362 F5.1 10-20W/m2 e_F6584 [-1/239] rms uncertainty on FNII
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Note (1): The equivalent width of the continuum-subtracted emission line
computed from straight integration over the bandpasses (emission is
negative). In general the EQW measurements provide a better measure of the
true equivalent width. The purpose of this measurement is to help
characterize the stellar absorption effecting the line.
(EWstellar=REW-EW), from SDSS.
Note (2): Flux from Gaussian fit to continuum subtracted data, in
10-17erg/s/cm2, from SDSS.
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History:
* 28-Apr-2015: From electronic version of the journal
* 07-Oct-2015: Reformatted for realistic significant figures.
(End) Patricia Vannier [CDS] 28-Apr-2015