199 research outputs found
The GALEX UV luminosity function of the cluster of galaxies Abell 1367
We present the GALEX NUV (2310 A) and FUV (1530 A) galaxy luminosity
functions of the nearby cluster of galaxies A1367 in the magnitude range -20.3<
M_AB < -13.3. The luminosity functions are consistent with previous (~ 2 mag
shallower) estimates based on the FOCA and FAUST experiments, but display a
steeper faint-end slope than the GALEX luminosity function for local field
galaxies. Using spectro-photometric optical data we select out star-forming
systems from quiescent galaxies and study their separate contributions to the
cluster luminosity function. We find that the UV luminosity function of cluster
star-forming galaxies is consistent with the field. The difference between the
cluster and field LF is entirely due to the contribution at low luminosities
(M_AB >-16 mag) of non star-forming, early-type galaxies that are significantly
over dense in clusters.Comment: 4 pages, 4 figures, 1 table. Accepted for publication in
Astrophysical Journal Letter
The Clustering of Extragalactic Extremely Red Objects
We have measured the angular and spatial clustering of 671 K5
Extremely Red Objects (EROs) from a 0.98 square degree sub-region of the NOAO
Deep Wide-Field Survey (NDWFS). Our study covers nearly 5 times the area and
has twice the sample size of any previous ERO clustering study. The wide field
of view and BwRIK passbands of the NDWFS allow us to place improved constraints
on the clustering of z=1 EROs. We find the angular clustering of EROs is
slightly weaker than in previous measurements, and w(1')=0.25+/-0.05 for
K<18.40 EROs. We find no significant correlation of ERO spatial clustering with
redshift, apparent color or absolute magnitude, although given the
uncertainties, such correlations remain plausible. We find the spatial
clustering of K5 EROs is well approximated by a power-law, with
r_0=9.7+/-1.1 Mpc/h in comoving coordinates. This is comparable to the
clustering of 4L* early-type galaxies at z<1, and is consistent with the
brightest EROs being the progenitors of the most massive ellipticals. There is
evidence of the angular clustering of EROs decreasing with increasing apparent
magnitude, when NDWFS measurements of ERO clustering are combined with those
from the literature. Unless the redshift distribution of K>20 EROs is very
broad, the spatial clustering of EROs decreases from r_0=9.7+/-1.1 Mpc/h for
K20 EROs.Comment: Accepted for publication in the ApJ. 29 pages with 10 figures. The
NOAO Deep Wide-Field Survey Bootes data release is available online at
http://www.noao.edu/noao/noaodeep
Endovascular Management of Juxtarenal and Pararenal Abdominal Aortic Aneurysms: Role of Chimney Technique
The use of chimney technique in endovascular repair of abdominal aortic aneurysms (ChEVAR) has had a secondary role. Although it was first
developed in an emergent/urgent setting, the publication of various important studies has helped overcome scepticism towards this technique
in elective procedures. This paper reviews current evidence about ChEVAR, focusing on clinical results, technical notes and comparisons with
other techniques. The new ChEVAR findings show favourable mid- and long-term clinical outcomes, even in elective patients. These results,
comparable to those related to fenestrated endografts, have been achieved through standardisation in planning and materials. An adequate
endograft oversizing associated to the right aortic neck length is fundamental to avoid ChEVAR-related complications, such as type 1a endoleaks.
These data indicate that ChEVAR, compared to other complex endovascular treatments, has comparable outcomes along with features that
could make it an essential option in every clinical settin
Ultraviolet through Infrared Spectral Energy Distributions from 1000 SDSS Galaxies: Dust Attenuation
The meaningful comparison of models of galaxy evolution to observations is
critically dependent on the accurate treatment of dust attenuation. To
investigate dust absorption and emission in galaxies we have assembled a sample
of ~1000 galaxies with ultraviolet (UV) through infrared (IR) photometry from
GALEX, SDSS, and Spitzer and optical spectroscopy from SDSS. The ratio of IR to
UV emission (IRX) is used to constrain the dust attenuation in galaxies. We use
the 4000A break as a robust and useful, although coarse, indicator of star
formation history (SFH). We examine the relationship between IRX and the UV
spectral slope (a common attenuation indicator at high-redshift) and find
little dependence of the scatter on 4000A break strength. We construct average
UV through far-IR spectral energy distributions (SEDs) for different ranges of
IRX, 4000A break strength, and stellar mass (M_*) to show the variation of the
entire SED with these parameters. When binned simultaneously by IRX, 4000A
break strength, and M_* these SEDs allow us to determine a low resolution
average attenuation curve for different ranges of M_*. The attenuation curves
thus derived are consistent with a lambda^{-0.7} attenuation law, and we find
no significant variations with M_*. Finally, we show the relationship between
IRX and the global stellar mass surface density and gas-phase-metallicity.
Among star forming galaxies we find a strong correlation between IRX and
stellar mass surface density, even at constant metallicity, a result that is
closely linked to the well-known correlation between IRX and star-formation
rate.Comment: 12 pages, 8 figures, 2 tables, appearing in the Dec 2007 GALEX
special issue of ApJ Supp (29 papers
Endovascular Management of Juxtarenal and Pararenal Abdominal Aortic Aneurysms: Role of Chimney Technique
Ultraviolet Imaging of the z=0.23 Cluster Abell 2246
We present deep ultraviolet observations of a field containing the cluster
Abell 2246 (z=0.225) which provide far-ultraviolet (FUV) images of some of the
faintest galaxies yet observed in that bandpass. Abell 2246 lies within the
field of view of Ultraviolet Imaging Telescope (UIT) observations of the quasar
HS1700+64, which accumulated over 7100 seconds of UIT FUV exposure time during
the Astro-2 mission in March 1995. For objects found on both the FUV and
ground-based V-band images, we obtain FUV (l ~ 1520 A) photometry and V-band
photometry, as well as mid-UV (l ~ 2490 A) photometry from UIT Astro-1
observations and ground-based I-band photometry. We find five objects in the
images which are probably galaxies at the distance of Abell 2246, with FUV
magnitudes (m(FUV)) between 18.6 and 19.6, and V magnitudes between 18.4 and
19.6. We find that their absolute FUV fluxes and colors imply strongly that
they are luminous galaxies with significant current star formation, as well as
some relatively recent, but not current, (> 400 Myr ago) star formation. We
interpret the colors of these five objects by comparing them with local
objects, redshift-corrected template spectra and stellar population models,
finding that they are plausibly matched by 10-Gyr-old population models with
decaying star formation, with decay time constants in the range 3 Gyr < t < 5
Gyr, with an additional color component from a single burst of moderate ( ~
400-500 Myr) age. From derived FUV luminosities we compute current star
formation rates. We compare the UV properties of Abell 2246 with those of the
Coma cluster, finding that Abell 2246 has significantly more recent star
formation, consistent with the Butcher-Oemler phenomenon.Comment: Accepted for publication in the Astronomical Journal, June 1998. 17
Pages AAS latex, includes 4 bitmap .jpg format images and 4 other figures.
PDF, Embedded Gzipped PS version (1.9Mb) TeX source and figures available at
http://www.astro.virginia.edu/~bd4r/galaxies.htm
HST Imaging of the Host Galaxies of High Redshift Radio-Loud Quasars
We present rest-frame UV and Ly-alpha images of spatially-resolved structures
around five high-redshift radio-loud quasars obtained with the WFPC2 camera on
the Hubble Space Telescope. We find that all five quasars are extended and this
"fuzz" contains ~5-40% of the total continuum flux and 15-65% of the Ly-alpha
flux within a radius of about 1.5 arcsec. The rest-frame UV luminosities of the
hosts are log lambda P_lambda = 11.9 to 12.5 solar luminosities (assuming no
internal dust extinction), comparable to the luminous radio galaxies at similar
redshifts and a factor 10 higher than both radio-quiet field galaxies at z~2-3
and the most UV-luminous low redshift starburst galaxies. The Ly-alpha
luminosities of the hosts are (in the log) approximately 44.3-44.9 erg/s which
are also similar to the those of luminous high redshift radio galaxies and
considerably larger than the Ly-alpha luminosities of high redshift field
galaxies. To generate the Ly-alpha luminosities of the hosts would require
roughly a few percent of the total observed ionizing luminosity of the quasar.
We find good alignment between the extended Ly-alpha and the radio sources,
strong evidence for jet-cloud interactions in two cases, again resembling radio
galaxies, and what is possibly the most luminous radio-UV synchrotron jet in
one of the hosts at z=2.110.Comment: 36 pages (latex, aas macros), 3 figures (3 gif and 10 postscript
files), accepted for publication in the the Astrophysical Journal Supplement
Serie
Large-Amplitude Ultraviolet Variations in the RR Lyrae Star ROTSE-I J143753.84+345924.8
The NASA Galaxy Evolution Explorer (GALEX) satellite has obtained
simultaneous near and far ultraviolet light curves of the ROTSE-I Catalog RR
Lyrae ab-type variable star J143753.84+345924.8. A series of 38 GALEX Deep
Imaging Survey observations well distributed in phase within the star's
0.56432d period shows an AB=4.9mag variation in the far UV (1350-1750A) band
and an AB=1.8mag variation in the near UV (1750-2750A) band, compared with only
a 0.8mag variation in the broad, unfiltered ROTSE-I (4500-10000A) band. These
GALEX UV observations are the first to reveal a large RR Lyrae amplitude
variation at wavelengths below 1800A. We compare the GALEX and ROTSE-I
observations to predictions made by recent Kurucz stellar atmosphere models. We
use published physical parameters for the comparable period (0.57433d),
well-observed RR Lyrae star WY Antliae to compute predicted FUV, NUV, and
ROTSE-I light curves for J143753.84+345924.8. The observed light curves agree
with the Kurucz predictions for [Fe/H]=-1.25 to within AB=0.2mag in the GALEX
NUV and ROTSE-I bands, and within 0.5mag in the FUV. At all metallicities
between solar and one hundredth solar, the Kurucz models predict 6-8mag of
variation at wavelengths between 1000-1700A. Other variable stars with similar
temperature variations, such as Cepheids, should also have large-amplitude FUV
light curves, observable during the ongoing GALEX imaging surveys.Comment: This paper will be published as part of the Galaxy Evolution Explorer
(GALEX) Astrophysical Journal Letters Special Issue. Links to the full set of
papers will be available at http:/www.galex.caltech.edu/PUBLICATIONS after
November 22, 200
The Local Universe as Seen in Far-Infrared and in Far-Ultraviolet: A Global Point of View on the Local Recent Star Formation
We select far-infrared (FIR-60 microns) and far-ultraviolet (FUV-1530 A)
samples of nearby galaxies in order to discuss the biases encountered by
monochromatic surveys (FIR or FUV). Very different volumes are sampled by each
selection and much care is taken to apply volume corrections to all the
analyses. The distributions of the bolometric luminosity of young stars are
compared for both samples: they are found to be consistent with each other for
galaxies of intermediate luminosities but some differences are found for high
(>5 10^{10} L_sun) luminosities. The shallowness of the IRAS survey prevents us
from securing comparison at low luminosities (<2 10^9 L_sun). The ratio of the
total infrared (TIR) luminosity to the FUV luminosity is found to increase with
the bolometric luminosity in a similar way for both samples up to 5 10^{10}
L_sun. Brighter galaxies are found to have a different behavior according to
their selection: the L_TIR/L_FUV ratio of the FUV-selected galaxies brighter
than 5 10^{10} L_sun reaches a plateau whereas L_TIR/L_FUV continues to
increase with the luminosity of bright galaxies selected in FIR. The
volume-averaged specific star formation rate (SFR per unit galaxy stellar mass,
SSFR) is found to decrease toward massive galaxies within each selection. The
SSFR is found to be larger than that measured for optical and NIR-selected
sample over the whole mass range for the FIR selection, and for masses larger
than 10^{10} M_sun for the FUV selection. Luminous and massive galaxies
selected in FIR appear as active as galaxies with similar characteristics
detected at z ~ 0.7.Comment: 32 pages, 9 figures, to be published in the Astrophysical Journal
Supplement series dedicated to GALEX result
GALEX UV Spectroscopy and Deep Imaging of LIRGs in the ELAIS S1 field
The ELAIS S1 field was observed by GALEX in both its Wide Spectroscopic and
Deep Imaging Survey modes. This field was previously observed by the Infrared
Space Observatory and we made use of the catalogue of multi-wavelength data
published by the ELAIS consortium to select galaxies common to the two samples.
Among the 959 objects with GALEX spectroscopy, 88 are present in the ELAIS
catalog and 19 are galaxies with an optical spectroscopic redshift. The
distribution of redshifts covers the range . The selected galaxies
have bolometric IR luminosities (deduced from the flux using ISOCAM) which means that we cover a wide range of galaxies from
normal to Ultra Luminous IR Galaxies. The mean () UV luminosity (not
corrected for extinction) amounts to
L_\sun for the low-z () sample. The UV slope (assuming
) correlates with the GALEX FUV-NUV color if
the sample is restricted to galaxies below . Taking advantage of the
UV and IR data, we estimate the dust attenuation from the IR/UV ratio and
compare it to the UV slope . We find that it is not possible to uniquely
estimate the dust attenuation from for our sample of galaxies. These
galaxies are highly extinguished with a median value .
Once the dust correction applied, the UV- and IR-based SFRs correlate. For the
closest galaxy with the best quality spectrum, we see a feature consistent with
being produced by a bump near 220nm in the attenuation curve.Comment: This paper has been published as part of the GALEX ApJL Special Issue
(ApJ 619, L63
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