15 research outputs found
Spectroscopy of KISS Emission-Line Galaxy Candidates. I. MDM Observations
Spectroscopic observations for 351 emission-line galaxy candidates from the KPNO International Spectroscopic Survey (KISS) have been obtained using the MDM Observatory 2.4 m telescope on Kitt Peak. KISS is an ongoing wide-field objective-prism survey for extragalactic emission-line objects, which has cataloged over 2200 emission-line galaxy (ELG) candidates to date. Spectroscopic follow-up observations are being carried out to study the characteristics of the survey objects. The observational data presented here include redshifts, reddening estimates, line equivalent widths, Hα line fluxes, and emission-line ratios. The galaxies have been classified based on their emission-line characteristics. The procedure for selecting the ELG candidates in KISS is found to be very reliable: 95% of the candidates in this sample are verified to have emission lines. A comparison of objective-prism survey dataâredshifts, Hα line fluxes, and equivalent widthsâwith the long-slit measurements shows good overall agreement
Spectroscopy of KISS Emission-Line Galaxy Candidates. III. A Second Set of MDM Observations
Spectroscopic observations for 315 emission-line galaxy (ELG) candidates from the KPNO International Spectroscopic Survey (KISS) have been obtained using the MDM Observatory 2.4 m telescope on Kitt Peak. KISS is a wide-field objective-prism survey for extragalactic emission-line objects that has cataloged over 2200 ELG candidates to date. Spectroscopic follow-up observations are being carried out to study the characteristics of the survey objects. The observational data presented here include redshifts, reddening estimates, line equivalent widths, Hα line fluxes, and emission-line ratios. The galaxies have been classified based on their emission-line characteristics. The procedure for selecting the ELG candidates in KISS is found to be very reliable: 93% of the candidates in this sample are verified to have emission lines. A comparison of objective-prism survey dataâredshifts, Hα line fluxes, and equivalent widthsâto the long-slit measurements shows good overall agreement
A Population of Metal-Poor Galaxies with ~L* Luminosities at Intermediate Redshifts
We present new spectroscopy and metallicity estimates for a sample of 15
star-forming galaxies with redshifts in the range 0.29 - 0.42. These objects
were selected in the KPNO International Spectroscopic Survey via their strong
emission lines seen in red objective-prism spectra. Originally thought to be
intermediate-redshift Seyfert 2 galaxies, our new spectroscopy in the far red
has revealed these objects to be metal-poor star-forming galaxies. These
galaxies follow a luminosity-metallicity (L-Z) relation that parallels the one
defined by low-redshift galaxies, but is offset by a factor of more than ten to
lower abundances. The amount of chemical and/or luminosity evolution required
to place these galaxies on the local L-Z relation is extreme, suggesting that
these galaxies are in a very special stage of their evolution. They may be
late-forming massive systems, which would challenge the current paradigm of
galaxy formation. Alternatively, they may represent intense starbursts in
dwarf-dwarf mergers or a major infall episode of pristine gas into a
pre-existing galaxy. In any case, these objects represent an extreme stage of
galaxy evolution taking place at relatively low redshift.Comment: 6 pages, 3 figures; to appear in 10 April 2009 ApJ
Structural and Photometric Classification of Galaxies - I. Calibration Based on a Nearby Galaxy Sample
In this paper we define an observationally robust, multi-parameter space for
the classification of nearby and distant galaxies. The parameters include
luminosity, color, and the image-structure parameters: size, image
concentration, asymmetry, and surface brightness. Based on an initial
calibration of this parameter space using the ``normal'' Hubble-types surveyed
by Frei et al. (1996), we find that only a subset of the parameters provide
useful classification boundaries for this sample. Interestingly, this subset
does not include distance-dependent scale parameters, such as size or
luminosity. The essential ingredient is the combination of a spectral index
(e.g., color) with parameters of image structure and scale: concentration,
asymmetry, and surface-brightness. We refer to the image structure parameters
(concentration and asymmetry) as indices of ``form.'' We define a preliminary
classification based on spectral index, form, and surface-brightness (a scale)
that successfully separates normal galaxies into three classes. We
intentionally identify these classes with the familiar labels of Early,
Intermediate, and Late. This classification, or others based on the above four
parameters can be used reliably to define comparable samples over a broad range
in redshift. The size and luminosity distribution of such samples will not be
biased by this selection process except through astrophysical correlations
between spectral index, form, and surface-brightness.Comment: to appear in AJ (June, 2000); 34 pages including 4 tables and 12
figure
The KPNO International Spectroscopic Survey. V. H-alpha-selected Survey List 3
The KPNO International Spectroscopic Survey (KISS) is an objective-prism
survey designed to detect extragalactic emission-line objects. It combines many
of the features of previous slitless spectroscopic surveys with the advantages
of modern CCD detectors, and is the first purely digital objective-prism survey
for emission-line galaxies (ELGs). Here we present the third list of ELG
candidates selected from our red spectral data, which cover the wavelength
range 6400 to 7200 A. In most cases, the detected emission line is H-alpha. The
current survey list covers the region of the NOAO Deep Wide-Field Survey
(NDWFS). This survey covers two fields; the first is 3 x 3 degrees square and
located at RA = 14h 30m, DEC = 34.5 deg (B1950), the second is 2.3 x 4.0
degrees and centered at RA = 2h 7.5m, DEC = -4.75 deg. A total area of 19.65
deg^2 is covered by the KISS data. A total of 261 candidate emission-line
objects have been selected for inclusion in the survey list (13.3 per deg^2).
We tabulate accurate coordinates and photometry for each source, as well as
estimates of the redshift, emission-line flux and line equivalent width based
on measurements of the digital objective-prism spectra. The properties of the
KISS ELGs are examined using the available observational data. When combined
with the wealth of multi-wavelength data already available for the NDWFS
fields, the current list of KISS ELGs should provide a valuable tool for
studying star-formation and nuclear activity in galaxies in the local universe.Comment: 18 pages, including 10 figures and 4 tables. Accepted for publication
in the December, 2005 A
The KPNO International Spectroscopic Survey. IV. H-alpha-selected Survey List 2
The KPNO International Spectroscopic Survey (KISS) is an objective-prism
survey for extragalactic emission-line objects. It combines many of the
features of previous slitless spectroscopic surveys with the advantages of
modern CCD detectors, and is the first purely digital objective-prism survey
for emission-line galaxies. Here we present the second list of emission-line
galaxy candidates selected from our red spectral data, which cover the
wavelength range 6400 to 7200 A. In most cases, the detected emission line is
H-alpha. The current survey list covers a 1.6-degree-wide strip located at
Dec(1950) = 43d 30' and spans the RA range 11h 55m to 16h 15m. The survey strip
runs through the center of the Bootes Void, and has enough depth to adequately
sample the far side of the void. An area of 65.8 sq. deg. is covered. A total
of 1029 candidate emission-line objects have been selected for inclusion in the
survey list (15.6 per sq. deg.). We tabulate accurate coordinates and
photometry for each source, as well as estimates of the redshift and
emission-line flux and equivalent width based on measurements of the digital
objective-prism spectra. The properties of the KISS emission-line galaxies are
examined using the available observational data. Although the current survey
covers only a modest fraction of the total volume of the Bootes Void, we
catalog at least twelve objects that appear to be located within the void. Only
one of these objects has been recognized previously as a void galaxy.Comment: Accepted for publication in the Astronomical Journal (April 2004); 20
pages, 12 figure
Metal Abundances of KISS Galaxies. IV. Galaxian Luminosity-Metallicity Relations in the Optical and Near-IR
We explore the galaxian luminosity-metallicity (L-Z) relationship in both the
optical and the near-IR using a combination of optical photometric and
spectroscopic observations from the KPNO International Spectroscopic Survey
(KISS) and near-infrared photometry from the Two-micron All Sky Survey (2MASS).
We supplement the 2MASS data with our own NIR photometry for a small number of
lower-luminosity ELGs that are under-represented in the 2MASS database. Our
B-band L-Z relationship includes 765 star-forming KISS galaxies with coarse
abundance estimates from our follow-up spectra, while the correlation with KISS
and 2MASS yields a total of 420 galaxies in our J-band L-Z relationship. We
explore the effect that changing the correlation between the strong-line
abundance diagnostic R_23 and metallicity has on the derived L-Z relation. We
find that the slope of the L-Z relationship decreases as the wavelength of the
luminosity bandpass increases. We interpret this as being, at least in part, an
effect of internal absorption in the host galaxy. Furthermore, the dispersion
in the L-Z relation decreases for the NIR bands, suggesting that variations in
internal absorption contribute significantly to the observed scatter. We
propose that our NIR L-Z relations are more fundamental than the B-band
relation, since they are largely free of absorption effects and the NIR
luminosities are more directly related to the stellar mass of the galaxy than
are the optical luminosities.Comment: 22 pages, including 6 figures and 6 tables. Accepted for publication
in the Astrophysical Journal (20 May 2005 issue