THE IDENTIFICATION OF LOW-REDSHIFT DLA, SUBDLA, AND LLS GALAXIES

Here we provide the images, photometry, and photometric redshift fits and stellar population synthesis model parameters for all of our fields from Rao et al. (2011). The paper describes the dataset and observational details. Four examples of the data and details on how the absorbing galaxies are identified are also given in the paper. Here, we provide similar information for the entire dataset. The table below is the observing sample. The quasar name links to the details pertaining to that field.
General Notes:

(1) All magnitudes reported in this paper are in the AB system, and all distance related quantities are calculated using the "737" cosmology with [Omega(Lambda), Omega(M), h] = [0.7,0.3,0.7].

(2) The detection and photometry of sources were carried out using the automated software SExtractor (Bertin \& Arnouts 1996). The SExtractor input parameter that defines the detection threshold for source identification was set to 1sigma above the sky background, and the minimum detection area was set to 5 adjoining pixels. "Adjoining" as implemented in SExtractor refers to any pixels touching at corners or sides. A source is considered to be a confident detection if it was detected at the 2 sigma or higher level through more than one filter. Its position was determined using the image with the best seeing.

(3) Only extended objects within an impact parameter b=100 kpc from the quasar at the absorber redshift (or lowest absorber redshift in the case of multiple absorbers per quasar sightline) are cataloged for each field, since galaxies farther away can statistically be considered background or foreground galaxies (see Rao et al. 2011).

(4) Sources are numbered in order of increasing impact parameter from the quasar, and ellipses are drawn around sources in each image only to guide the eye. Photometry tables give positions relative to the quasar, AB magnitudes, and the detection significance, "DS", which is defined as the number of standard deviations the source is detected above the background. DS = S/(B imes N_{pix}), where S is the net source counts, B is the counts per pixel that correspond to a source detected at 1 sigma above the background, and N_{pix} is the number of pixels within the detection isophote. A source is considered to be a detection if DS >= 2 and N_{pix} >= 5.

(5) Photometric redshifts were determined for galaxies that were detected in four or more filters. We sometimes used SDSS photometry to supplement our IR measurements. Tables describing photometric redshift fits give details of the stellar population templates that best fit the photometry. The information provided includes object number as marked on the images and its projected distance from the quasar in arcsec and kpc assuming that the galaxy is at the absorption redshift, age of the stellar population, star formation rate e-folding time, tau, extinction, E(B-V), metal mass fraction, Z (Z_\odot = 0.2), and the photometric redshift and error.

(6) The absorbing galaxy has not been confirmed spectroscopically for any of the fields presented here. Photometric redshifts, galaxy colors, and proximity to the quasar sightline, in decreasing order of importance, are used to identify galaxies responsible for the absorption. Measured galaxy colors are compared with the colors derived from the redshifted "hyperz" galaxy templates of Hewett et al. (2006, MNRAS, 367, 454), after converting our AB magnitudes to Vega magnitudes, to constrain galaxy redshifts. If more than one galaxy has a photometric redshift or color that matches the absorption redshift, then the one closest to the quasar sightline is selected as the absorber. For sightlines with two absorbers, assignment of the absorbing galaxies was often ambiguous. Depending on the specifics of the field, we were sometimes unable to assign a galaxy to the absorber.

(7) While we cannot be absolutely certain that the correct identification has been made in any individual field, our statistical results are almost certainly reliable. Thus, the strength of this investigation lies in our large statistical sample.

(8) When available, we provide the photometric redshift of an object as listed in the SDSS database. We use the "photozcc2" parameter since this estimator is appropriate for the entire range of magnitudes measured in the SDSS. See Oyaizu et al. (2008, ApJ, 674, 768). Otherwise, the photometric redshift labelled "photoZ" is used.


Viewing the Data Set


To see the associated images and measurements for a given field along with a description of what is available, please click on the field name link in the table below.
Quasar
z-em
z-abs
1.245
0.520
1.245
0.942
3.053
0.863
1.959
0.613
0.738
0.526
1.282
0.913
1.491
0.576
1.491
1.048
1.551
0.869
1.551
1.409
1.340
0.782
1.384
0.683
1.450
0.471
0.589
0.482
0.837
0.771
1.035
0.632
1.349
0.725
1.849
0.212
0.915
0.633
1.343
0.860
1.343
1.153
0.000
0.424
1.877
0.606
1.383
0.638
0.907
0.672
1.244
0.843
1.244
0.887
1.699
0.971
1.319
0.346
1.531
0.632
1.531
0.709
0.740
0.573
1.649
0.720
1.392
0.740
1.392
1.070
0.957
0.418
0.957
0.552
2.193
0.393
2.193
0.629
1.226
0.773
2.305
0.938
1.390
0.716
0.787
0.538
1.095
0.606
2.006
0.859
2.006
0.886
2.006
1.421
0.969
0.624
0.969
0.821
1.333
0.735
1.333
0.842
1.190
0.609
1.190
0.687
1.275
0.738
1.275
0.928
1.090
0.872
1.318
0.959
0.801
0.567
0.927
0.656
0.927
0.891
0.371
0.222
1.252
0.748
0.697
0.558
0.937
0.530
1.215
0.634
1.444
0.945
1.444
1.031
1.342
0.554
1.072
0.998
1.578
0.715
1.578
1.234
1.538
0.911
1.538
1.002
2.706
0.633
1.404
0.847
1.308
0.652
1.040
0.471
0.765
0.604
[1]