J/ApJ/738/136 LAEs between 0.19<z<1.25 with GALEX grism (Cowie+, 2011)
Lyα emitting galaxies as early stages in galaxy formation.
Cowie L.L., Barger A.J., Hu E.M.
<Astrophys. J., 738, 136 (2011)>
=2011ApJ...738..136C 2011ApJ...738..136C
ADC_Keywords: Equivalent widths ; Galaxies, spectra ; Redshifts ; Ultraviolet
Keywords: cosmology: observations - galaxies: abundances - galaxies: starburst -
galaxies: distances and redshifts - galaxies: evolution
Abstract:
We present optical spectroscopy of two samples of Galaxy Evolution
Explorer grism selected Lyα emitters (LAEs): one at z=0.195-0.44
and the other at z=0.65-1.25. We have also observed a comparison
sample of galaxies in the same redshift intervals with the same UV
magnitude distributions but with no detected Lyα. We use the
optical spectroscopy to eliminate active galactic nuclei and to obtain
the optical emission-line properties of the samples. We compare the
luminosities of the LAEs in the two redshift intervals and show that
there is dramatic evolution in the maximum Lyα luminosity over
z=0-1. Focusing on the z=0.195-0.44 samples alone, we show that there
are tightly defined relations between all of the galaxy parameters and
the rest-frame equivalent width (EW) of Hα. The higher
EW(Hα) sources all have lower metallicities, bluer colors,
smaller sizes, and less extinction, consistent with their being in the
early stages of the galaxy formation process.
Description:
For the present study we use the LAE samples with rest-frame
EW(Lyα)>15Å from Cowie et al. (2010; Cat. J/ApJ/711/928),
chosen from the nine blank high-galactic latitude fields with the
deepest GALEX grism spectroscopic observations. The area covered is
just over 8deg2. The samples consist of sources whose grism UV
spectra have a detectable single emission line, which we assume to be
Lyα.
For the CDFS 00 field (53.12779 -27.87137; J2000), we have obtained
much deeper GALEX grism spectroscopic observations from MAST and
analyzed them to search for Lyα emission using the same
procedures as in Cowie et al. (2010; Cat. J/ApJ/711/928). We find a
sample of 100 Lyα selected sources within a 32.5' radius field
(Table 4).
We compiled ancillary data from various archival sources. Just over
82% of the area is covered by deep U-band images obtained with the
MegaPrime camera on the 3.6m Canada-France-Hawaii Telescope (CFHT).
See section 2.1 for the full list of sources.
We obtained optical spectroscopy for a large fraction of the two GALEX
LAE samples using the DEIMOS spectrograph on Keck II in observing runs
throughout 2009 and 2010. The ∼0.5-1.0hr spectra have a resolution of
4.5Å and a wavelength range of approximately 5000Å centered at
6800Å.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 136 61 z=0.195-0.44 LAE sample (EWLyα=20-148)
table2.dat 136 32 z=0.195-0.44 LAE sample (EWLyα=15-19)
table3.dat 123 8 z=0.65-1.25 LAE sample
table4.dat 96 100 GALEX spectral sample identifications: CDFS 00
--------------------------------------------------------------------------------
See also:
J/ApJ/711/928 : Low-redshift Lyα galaxies from GALEX (Cowie+, 2010)
J/A+A/512/A12 : VLT/VIMOS spectroscopy in GOODS-South field (Balestra+, 2010)
J/A+A/478/83 : GOODS-South Field VLT/FORS2 redshifts. III. (Vanzella+, 2008)
J/ApJ/680/1072 : Lyα-emitting galaxies at 0.2<z<0.35 (Deharveng+, 2008)
J/ApJS/161/21 : Extended Chandra Deep Field-South survey (Lehmer+, 2005)
Byte-by-byte Description of file: table[123].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- --- [GALEX]
6- 14 A9 --- GALEX Name (HHMM+DDMM; J2000)
15 A1 --- m_GALEX [abc] Multiplicity index (G1)
16- 25 F10.6 deg RAdeg Right ascension in decimal degrees (J2000)
27- 36 F10.6 deg DEdeg Declination in decimal degrees (J2000)
38- 43 F6.4 --- z GALEX redshift
45- 49 F5.2 [10-7W] logLnu Log of the bolometric continuum luminosity,
above 1216Å
51- 55 F5.2 [10-7W] logLa Log of the Lyα luminosity
57- 59 I3 0.1nm EWLya Rest-frame equivalent width(Lyα) in Å
61- 62 I2 0.1nm e_EWLya EWLya uncertainty
64- 70 F7.5 --- zOpt ? Optical ground-based redshift
71 A1 --- f_zOpt [ABD] Flag on optical data (1)
73- 77 A5 --- OType Optical type (Sy1.8, Sy1.5 or STAR)
79- 83 F5.1 0.1nm EWHa ? Rest-frame Hα equivalent width
in Å (or Hβ EW for table 3)
85- 88 F4.1 0.1nm e_EWHa ? EWHa uncertainty
90- 94 F5.3 --- [NII]/Ha ? [NII]6584 to Hα(6563) ratio
96-100 F5.3 --- e_[NII]/Ha ? [NII]/Ha uncertainty
102-106 F5.3 --- [OIII]/Hb ? [OIII]5007 to Hβ(4861) ratio
108-112 F5.3 --- e_[OIII]/Hb ? [OIII]/Hb uncertainty
114-118 F5.3 --- [OIII]/Hg ? [OIII]4363 to Hγ(4341) ratio
120-124 F5.3 --- e_[OIII]/Hg ? [OIII]/Hg uncertainty
126-130 F5.1 [mW/m2] logFHa ? Log of Hα flux (erg/cm2/s) (2)
132-136 F5.1 [mW/m2] logFHb ? Log of Hβ flux (erg/cm2/s) (2)
--------------------------------------------------------------------------------
Note (1): Flag as follows:
D = The optical redshift does not agree with the GALEX redshift.
B = AGN identified in the BPT diagram (Baldwin, Phillips and Terlevich.
1981PASP...93....5B 1981PASP...93....5B): [NII]/Hα versus [OIII]/Hβ
A = Galaxies with weak optical emission lines.
Note (2): The logarithm of the Hα and Hβ fluxes for the sources
with optical continuum magnitudes in the Sloan Digital Sky Survey
(SDSS; see Section 2.1).
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq [1/100] Running sequential number
(<[CBH2011] NNN> in Simbad)
5- 9 A5 --- --- [GALEX]
10- 18 A9 --- GALEX Name (HHMM+DDMM; J2000)
19 A1 --- m_GALEX [abc*] Multiplicity index (G1)
20- 29 F10.6 deg RAdeg Right ascension in decimal degrees (J2000)
31- 40 F10.6 deg DEdeg Declination in decimal degrees (J2000)
42- 48 F7.2 mag NUV ?=-999 NUV band magnitude
50- 56 F7.2 mag FUV ?=-999 FUV band magnitude
58- 62 F5.3 --- z [0.202/1.235] GALEX redshift from Lyα
emission line
64- 68 I5 km/s Width Lyα line width
70- 72 I3 km/s e_Width Width uncertainty
74- 76 A3 --- UVT [AGN] UV classification (AGN) (1)
78- 83 F6.4 --- zOpt ? Optical redshift
84 A1 --- r_zOpt [l] l = optical redshift from litterature (2)
86- 89 A4 --- OType [star] Optical type (star)
91 A1 --- f_logLX [E] Source within ECDF-S (3)
93- 96 F4.1 [10-7W] logLX [40.9/44]? Log of the rest-frame 2-8keV
luminosity (3)
--------------------------------------------------------------------------------
Note (1): The galaxy is classified as an AGN based on the presence of
high-excitation lines in the UV spectrum.
Note (2): The optical redshifts are primarily taken from our DEIMOS
spectroscopy, but we also include redshifts from Balestra et al.
(2010, Cat. J/A+A/512/A12) and Vanzella et al. (2008,
Cat. J/A+A/478/83).
Note (3): E = Where a source lies within the X-ray observations of the Extended
Chandra Deep Field-South (ECDF-S) and is not detected in X-rays
(Lehmer et al. 2005, Cat. J/ApJS/161/21). If the source is detected in
X-rays, the logarithm of the rest-frame 2-8keV luminosity is given.
--------------------------------------------------------------------------------
Global Notes:
Note (G1): GALEX names being ambiguous, the multiplicity index m_GALEX
was added at CDS (blank for unambiguous names; a, b or c in order
of increasing right ascension). The asterisk (*) flags the duplicate
sources in table2 (GALEX0331-2809 and GALEX1420+5250)
Nomenclature Notes:
In tables 1-4: objects are <[CBH2010] DDD.dddddd+DD.dddddd> in Simbad.
History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 16-Jan-2013