J/ApJ/765/26 Very low-z SDSS galaxies with Hα emission (Shim+, 2013)
Dissection of Hα emitters : low-z analogs of z > 4 star-forming galaxies.
Shim H., Chary R.-R.
<Astrophys. J., 765, 26 (2013)>
=2013ApJ...765...26S 2013ApJ...765...26S
ADC_Keywords: Galaxies, spectra ; Equivalent widths ; Redshifts ; Ultraviolet
Keywords: cosmology: observations; galaxies: evolution; galaxies: starburst
Abstract:
Strong Hα emitters (HAEs) dominate the z∼4 Lyman-break galaxy
(LBG) population. We have identified local analogs of these HAEs using
the Sloan Digital Sky Survey. At z<0.4, only 0.04% of the galaxies are
classified as HAEs with Hα equivalent widths (≳500Å)
comparable to that of z∼4 HAEs. Local HAEs have lower stellar mass and
lower ultraviolet (UV) luminosity than z∼4 HAEs, yet the
Hα-to-UV luminosity ratio, as well as their specific star
formation rate, is consistent with that of z∼4 HAEs, indicating that
they are scaled-down versions of high-z star-forming galaxies.
Compared to the previously studied local analogs of LBGs selected
using rest-frame UV properties, local HAEs show similar UV luminosity
surface density, weaker Dn(4000) break, lower metallicity, and lower
stellar mass. This implies that the local HAEs are less evolved
galaxies than the traditional Lyman break analogs. In the stacked
spectrum, local HAEs show a significant He IIλ4686 emission
line suggesting a population of hot, massive stars similar to that
seen in some Wolf-Rayet galaxies. Low [N II]/[O III] line flux ratios
imply that local HAEs are inconsistent with being systems that host
bright active galactic nuclei. Instead, it is highly likely that local
HAEs are galaxies with an elevated ionization parameter, either due to
a high electron density or large escape fraction of hydrogen ionizing
photons as in the case of Wolf-Rayet galaxies.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 99 299 Local strong Hα emitters (HAEs)
--------------------------------------------------------------------------------
See also:
II/311 : WISE All-Sky Data Release (Cutri+ 2012)
II/312 : GALEX-DR5 (GR5) sources from AIS and MIS (Bianchi+ 2011)
J/MNRAS/421/1043 : Emission-line galaxies from SDSS DR7 (Shirazi+, 2012)
J/ApJS/173/441 : UV-Luminous galaxies discovered by GALEX (Hoopes+, 2007)
J/ApJ/655/851 : Wolf-Rayet galaxies in the SDSS (Zhang+, 2007)
J/ApJ/647/128 : Hα observations of UV-selected galaxies (Erb, 2006)
J/ApJS/161/240 : High-ionization emission in metal-deficient BCD (Thuan+, 2005)
J/ApJS/132/37 : Spectroscopy of Southern warm IR galaxies (Kewley+, 2001)
http://www.mpa-garching.mpg.de/SDSS/DR7 : MPA-JHU catalog for SDSS-DR7
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 I18 --- objID SDSS identifier
20- 29 F10.6 deg RAdeg Right Ascension in decimal degrees (J2000)
31- 39 F9.6 deg DEdeg Declination in decimal degrees (J2000)
41- 48 F8.6 --- z [0.0009/0.4] Redshift (1)
50- 55 F6.1 0.1nm W(Ha) [500/2271] Hα equivalent width;
in Angstroms (1)
57- 63 F7.1 10-20W/m2 f(Ha) Hα line flux (10-17erg/s/cm2) (1)
65- 70 F6.3 [Lsun/kpc2] logIFUV ? FUV luminosity surface density (2)
72- 77 F6.3 [Msun/yr] logSFR Star formation rate (1)
79- 83 F5.3 [Msun] logM* [6/9.8]? Log of stellar mass (1)
85- 89 F5.3 [-] [O/H] [7.6/9.3]? Oxygen abundance 12+log[O/H] (1)
91- 96 F6.4 --- Dn4000 Strength of the 4000Å break (1)
98- 99 A2 --- WR [WR ] if matched with Wolf-Rayet galaxies
(Brinchmann et al. 2008MNRAS.385..769B 2008MNRAS.385..769B)
--------------------------------------------------------------------------------
Note (1): from MPA-JHU value added catalog for SDSS DR7 at
http://www.mpa-garching.mpg.de/SDSS/DR7/
Note (2): FUV luminosity is derived using GALEX FUV magnitude, and is divided
by 2πrhl2, where rhl is half-light radius in SDSS u-band.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 29-Oct-2014