J/ApJ/671/1227 Lyα galaxies at z∼4.5 (Dawson+, 2007)
A luminosity function of Lyα-emitting galaxies at z ∼ 4.5.
Dawson S., Rhoads J.E., Malhotra S., Stern D., Wang J., Dey A., Spinrad H.,
Jannuzi B.T.
<Astrophys. J., 671, 1227-1240 (2007)>
=2007ApJ...671.1227D 2007ApJ...671.1227D
ADC_Keywords: Galaxies, spectra ; Ultraviolet ; Redshifts ; Equivalent widths
Keywords: cosmology: observations - early universe - galaxies: evolution -
galaxies: formation - galaxies: high-redshift
Abstract:
We present a catalog of 59 z∼4.5 Lyα-emitting galaxies
spectroscopically confirmed in a campaign of Keck DEIMOS follow-up
observations to candidates selected in the Large Area Lyα (LALA)
narrowband imaging survey. We targeted 97 candidates for spectroscopic
follow-up; by accounting for the variety of conditions under which we
performed spectroscopy, we estimate a selection reliability of ∼76%.
Together with our previous sample of Keck LRIS confirmations, the 59
sources confirmed herein bring the total catalog to 73
spectroscopically confirmed z∼4.5 Lyα-emitting galaxies in the
∼0.7deg2 covered by the LALA imaging.
Description:
The LALA survey concentrates on two primary fields, "Bootes"
(14:25:57+35:32 [J2000.0]) and "Cetus" (02:05:20-04:5 [J2000.0]).
Observations were made with the Mosaic CCD cameras on the 4m Mayall
Telescope at Kitt Peak National Observatory and on the 4m Blanco
Telescope at Cerro Tololo Inter-American Observatory.
Between 2003 March and 2004 May we obtained spectroscopy of 97 z∼4.5
candidate Lyα-emitters with DEIMOS.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 89 59 Spectroscopic properties of the sample
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See also:
J/AJ/127/213 : LALA Bootes field X-ray source catalog (Wang+, 2004)
J/ApJ/669/765 : Chandra X-ray sources in LALA Cetus field (Wang+, 2007)
J/A+A/461/823 : Candidate Lyα emitting galaxies (Venemans+, 2007)
J/ApJ/614/75 : Lyα emitting galaxies at z=2.38 (Francis+, 2004)
J/ApJ/667/79 : Lyα emission-line galaxies at z=3.1 (Gronwall+, 2007)
J/ApJ/680/1072 : Lyα-emitting galaxies at 0.2<z<0.35 (Deharveng+, 2008)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- Target Target name (JHHMMSS.s+DDMMSS),
LALA JHHMMSS+DDMMSS in Simbad
18- 22 F5.3 --- z Redshift (1)
24- 28 F5.2 10-20W/m2 FLya Lyα flux (2)
30- 33 F4.2 10-20W/m2 e_FLya rms uncertainty on FLya
35 A1 --- l_EW Limit flag on EW
36- 38 I3 0.1nm EW Rest-frame equivalent width (3)
39 A1 --- n_EW [g] Note on EW limit value (7)
41- 44 I4 0.1nm E_EW ? Error on EW (upper value)
46- 48 I3 0.1nm e_EW ? Error on EW (lower value)
50- 53 F4.1 0.1nm FWHM FWHM of emission line (4)
55- 57 F3.1 0.1nm e_FWHM rms uncertainty on FWHM
59 A1 --- l_Dv Limit flag on Dv
60- 62 I3 km/s Dv Velocity width (5)
63 A1 --- n_Dv [h] h: This line is unresolved
65- 70 F6.3 uJy Cblue Blue-side continuum measurement (6)
72- 76 F5.3 uJy e_Cblue rms uncertainty on Cblue
78- 83 F6.3 uJy Cred Red-side continuum measurement (6)
85- 89 F5.3 uJy e_Cred rms uncertainty on Cred
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Note (1): The redshift was derived from the wavelength of the peak pixel in
the line profile smoothed with a 3 pixel boxcar average. We estimate
the error in this measurement to be δz∼0.0005, based on Monte
Carlo simulations in which we added random noise to each pixel of
every spectrum according to the photon counting statistics, and then
remeasured the redshift in each case. This measurement may
overestimate the true redshift of the system since the blue wing of
the Lyα emission is absorbed by foreground neutral hydrogen.
Note (2): The line flux was determined by totaling the flux of the pixels
that fall within the line profile. No attempt was made to model the
emission line or to account for the very minor contribution of the
continuum to the line. Quoted uncertainties account for photon
counting errors alone, excluding possible systematic errors. Despite
these caveats, the Lyα line fluxes measured from the pectra
agree with narrowband imaging to 1σ in all but three cases.
Note (3): The rest-frame equivalent widths were determined with
EW=(Fl/flambda,r)/(1+z), where Fl is the flux in the emission
line and flambda,r is the measured red-side continuum flux density.
The error bars δEW+ and δEW- are 1σ confidence
intervals determined by integrating over the probability density
functions Pi(EW) described in Sect. 4.1. The error bars are
symmetric in probability density space in the sense that
∫(EW,EW,dEW)Pi(EW')dEW'=∫(EW+dEW,EW)Pi(EW')dEW'=0.34
Note (4): The FWHM was measured directly from the emission line by counting
the number of pixels in the unsmoothed spectrum that exceed a flux
equal to half the flux in the peak pixel. No attempt was made to
account for the minor contribution of the continuum to the height of
the peak pixel. The error bars were determined with Monte Carlo
simulations in which we modeled each emission line with the truncated
Gaussian profile described in Hu et al. (2004AJ....127..563H 2004AJ....127..563H) and
Rhoads et al. (2004ApJ...611...59R 2004ApJ...611...59R) added random noise in each pixel
according to the photon counting errors and then measured the widths
σ(FWHM) of the resulting distribution of FWHM for the given line.
Note (5): The velocity width was determined by subtracting in quadrature
the effective instrumental resolution for a point source and is
therefore an upper limit, as the target may have angular size
comparable to the ≳1" seeing of these data. Where the emission line
is unresolved, the velocity width is an upper limit set by the
effective width of the resolution element itself.
Note (6): Red- and blue-side continuum measurements are variance-weighted
averages made in 1200Å wide windows beginning 30Å from the
wavelength of the peak pixel in the emission line. We employed a 10
iteration, 2σ clipping algorithm to reduce the effect of
spurious outliers occurring at long wavelength, where the sky noise is
large. In some cases, a small correction factor was subtracted from
the variance-weighted averages based on the detection of residual
signal remaining in extractions of source-free, sky-subtracted regions
of the two-dimensional spectra (see text, Sect. 2.2). Quoted
uncertainties account for photon counting errors in the source
extractions added in quadrature to the photon-counting errors derived
in the blank-sky extractions.
Note (7): A 2σ lower limit. The measurement of the red-side continuum
for this source is formally consistent with no observable flux. The
equivalent width limit was then set by using a 2σ upper limit to
flambda,r in the expression given in note (3).
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History:
From electronic version of the journal
References:
Dawson et al., Paper I 2004ApJ...617..707D 2004ApJ...617..707D
(End) Patricia Vannier [CDS] 24-Mar-2010