4,882 research outputs found
A catalog of Kazarian galaxies
The entire Kazarian galaxies (KG) catalog is presented which combines
extensive new measurements of their optical parameters with a literature and
database search. The measurements were made using images extracted from the
STScI Digitized Sky Survey (DSS) of Jpg(blue), Fpg(red) and Ipg(NIR) band
photographic sky survey plates obtained by the Palomar and UK Schmidt
telescopes. We provide accurate coordinates, morphological type, spectral and
activity classes, blue apparent diameters, axial ratios, position angles, red,
blue and NIR apparent magnitudes, as well as counts of neighboring objects in a
circle of radius 50 kpc from centers of KG. Special attention was paid to the
individual descriptions of the galaxies in the original Kazarian lists, which
clarified many cases of misidentifications of the objects, particularly among
interacting systems. The total number of individual Kazarian objects in the
database is now 706. We also include the redshifts which are now available for
404 galaxies and the 2MASS infrared magnitudes for 598 KG. The database also
includes extensive notes, which summarize information about the membership of
KG in different systems of galaxies, and about revised activity classes and
redshifts. An atlas of several interesting subclasses of KG is also presented.Comment: 15 pages, 5 figures, 1 table, Accepted in Astrophysics, Vol. 53, No.
1, 2010 (English translation of Astrofizika
On the fairness of the main galaxy sample of SDSS
Flux-limited and volume-limited galaxy samples are constructed from SDSS data
releases DR4, DR6 and DR7 for statistical analysis. The two-point correlation
functions , monopole of three-point correlation functions ,
projected two-point correlation function and pairwise velocity dispersion
are measured to test if galaxy samples are fair for these
statistics. We find that with increment of sky coverage of SDSS, of
flux-limited sample is extremely robust and insensitive to local structures at
low redshift. But for volume-limited samples fainter than at large scales
s>\sim 10\hmpc, deviation of and of DR7 to those of DR4
and DR6 increases with larger absolute magnitude. In the weakly nonlinear
regime, there is no agreement between of different data releases in
all luminosity bins. Furthermore, of volume-limited samples of DR7 in
luminosity bins fainter than are significantly larger,
and of the two faintest volume-limited samples of DR7 display
very different scale dependence than results of DR4 and DR6. Our findings call
for cautions in understanding clustering analysis results of SDSS faint galaxy
samples, and higher order statistics of SDSS volume-limited samples in the
weakly nonlinear regime. The first zero-crossing points of of
volume-limited samples are also investigated and discussed.Comment: 16 pages, 12 figures, accepte
Precise absolute astrometry from the VLBA imaging and polarimetry survey at 5 GHz
We present in this paper accurate positions of 857 sources derived from the
astrometric analysis of 16 eleven-hour experiments from the Very Long Baseline
Array imaging and polarimetry survey at 5 GHz (VIPS). Among observed sources,
positions of 430 objects were not determined before at a milliarcsecond level
of accuracy. For 95% of the sources the uncertainty of their positions range
from 0.3 to 0.9 mas, with the median value of 0.5 mas. This estimate of
accuracy is substantiated by the comparison of positions of 386 sources that
were previously observed in astrometric programs simultaneously at 2.3/8.6 GHz.
Surprisingly, the ionosphere contribution to group delay was adequately modeled
with the use of the total electron contents maps derived from GPS observations
and only marginally affected estimates of source coordinates.Comment: Accepted for publication by the Astronomical Journal. 7 pages, 2
tables, 4 figures. Submission contains an ascii file with the catalogue. You
can get the catalogue by downloading the source of this paper and extracting
file table2.tx
Photometric observations of selected, optically bright quasars for Space Interferometry Mission and other future celestial reference frames
Photometric observations of 235 extragalactic objects that are potential
targets for the Space Interferometry Mission (SIM) are presented. Mean B, V, R,
I magnitudes at the 5% level are obtained at 1 - 4 epochs between 2005 and 2007
using the 1-m telescopes at Cerro Tololo Inter-American Observatory and Naval
Observatory Flagstaff Station. Of the 134 sources which have V magnitudes in
the Veron & Veron-Cetty catalog a difference of over 1.0 mag is found for the
observed-catalog magnitudes for about 36% of the common sources, and 10 sources
show over 3 mag difference. Our first set of observations presented here form
the basis of a long-term photometric variability study of the selected
reference frame sources to assist in mission target selection and to support in
general QSO multi-color photometric variability studies.Comment: 40 pages, 13 figures, 4 table
The Presence of Weak Active Galactic Nuclei in High Redshift Star Forming Galaxies
We present [OIII 5007A] observations of the star forming galaxy HDF-BMZ1299
(z=1.598) using Keck Observatory's Adaptive Optics system with the
near-infrared integral field spectrograph OSIRIS. Using previous Halpha and
[NII] measurements of the same source, we are able for the first time to use
spatially resolved observations to place a high-redshift galaxy's substructure
on a traditional HII diagnostic diagram. We find that HDF-BMZ1299's spatially
concentrated nebular ratios in the central ~1.5 kiloparsec (0."2) are best
explained by the presence of an AGN: log([NII]/Halpha)=-0.22+/-0.05 and 2sigma
limit of log([OIII]/Hbeta)>0.26. The dominant energy source of this galaxy is
star formation, and integrating a single aperture across the galaxy yields
nebular ratios that are composite spectra from both AGN and HII regions. The
presence of an embedded AGN in HDF-BMZ1299 may suggest a potential
contamination in a fraction of other high-redshift star forming galaxies, and
we suggest that this may be a source of the "elevated" nebular ratios
previously seen in seeing-limited metallicity studies. HDF-BMZ1299's estimated
AGN luminosity is L_Halpha = 3.7e41 erg/s and L_[OIII] = 5.8e41 erg/s, making
it one of the lowest luminosity AGN discovered at this early epoch.Comment: 15 pages, 4 figures, ApJ Accepted, new version to be published
(updated text, figures, and table
Reconstructing Theory from Ricci Dark Energy
In this letter, we regard the theory as an effective description for
the acceleration of the universe and reconstruct the function from the
Ricci dark energy, which respects holographic principle of quantum gravity. By
using different parameter in RDE, we show the behaviors of
reconstructed and find they are much different in the future.Comment: 16 pages, 7 figure
Constraining the interacting dark energy models from weak gravity conjecture and recent observations
We examine the effectiveness of the weak gravity conjecture in constraining
the dark energy by comparing with observations. For general dark energy models
with plausible phenomenological interactions between dark sectors, we find that
although the weak gravity conjecture can constrain the dark energy, the
constraint is looser than that from the observations.Comment: 14 pages, 12 figures, revtex4, v2: minor corrections, accepted for
publication in PL
Measuring large-scale structure with quasars in narrow-band filter surveys
We show that a large-area imaging survey using narrow-band filters could
detect quasars in sufficiently high number densities, and with more than
sufficient accuracy in their photometric redshifts, to turn them into suitable
tracers of large-scale structure. If a narrow-band optical survey can detect
objects as faint as i=23, it could reach volumetric number densities as high as
10^{-4} h^3 Mpc^{-3} (comoving) at z~1.5 . Such a catalog would lead to
precision measurements of the power spectrum up to z~3-4. We also show that it
is possible to employ quasars to measure baryon acoustic oscillations at high
redshifts, where the uncertainties from redshift distortions and nonlinearities
are much smaller than at z<1. As a concrete example we study the future impact
of J-PAS, which is a narrow-band imaging survey in the optical over 1/5 of the
unobscured sky with 42 filters of ~100 A full-width at half-maximum. We show
that J-PAS will be able to take advantage of the broad emission lines of
quasars to deliver excellent photometric redshifts, \sigma_{z}~0.002(1+z), for
millions of objects.Comment: Matches version published in MNRAS (2012
Does training with amplitude modulated tones affect tone-vocoded speech perception?
Temporal-envelope cues are essential for successful speech perception. We asked here whether training on stimuli containing temporal-envelope cues without speech content can improve the perception of spectrally-degraded (vocoded) speech in which the temporal-envelope (but not the temporal fine structure) is mainly preserved. Two groups of listeners were trained on different amplitude-modulation (AM) based tasks, either AM detection or AM-rate discrimination (21 blocks of 60 trials during two days, 1260 trials; frequency range: 4Hz, 8Hz, and 16Hz), while an additional control group did not undertake any training. Consonant identification in vocoded vowel-consonant-vowel stimuli was tested before and after training on the AM tasks (or at an equivalent time interval for the control group). Following training, only the trained groups showed a significant improvement in the perception of vocoded speech, but the improvement did not significantly differ from that observed for controls. Thus, we do not find convincing evidence that this amount of training with temporal-envelope cues without speech content provide significant benefit for vocoded speech intelligibility. Alternative training regimens using vocoded speech along the linguistic hierarchy should be explored
The WiggleZ Dark Energy Survey: Direct constraints on blue galaxy intrinsic alignments at intermediate redshifts
Correlations between the intrinsic shapes of galaxy pairs, and between the
intrinsic shapes of galaxies and the large-scale density field, may be induced
by tidal fields. These correlations, which have been detected at low redshifts
(z<0.35) for bright red galaxies in the Sloan Digital Sky Survey (SDSS), and
for which upper limits exist for blue galaxies at z~0.1, provide a window into
galaxy formation and evolution, and are also an important contaminant for
current and future weak lensing surveys. Measurements of these alignments at
intermediate redshifts (z~0.6) that are more relevant for cosmic shear
observations are very important for understanding the origin and redshift
evolution of these alignments, and for minimising their impact on weak lensing
measurements. We present the first such intermediate-redshift measurement for
blue galaxies, using galaxy shape measurements from SDSS and spectroscopic
redshifts from the WiggleZ Dark Energy Survey. Our null detection allows us to
place upper limits on the contamination of weak lensing measurements by blue
galaxy intrinsic alignments that, for the first time, do not require
significant model-dependent extrapolation from the z~0.1 SDSS observations.
Also, combining the SDSS and WiggleZ constraints gives us a long redshift
baseline with which to constrain intrinsic alignment models and contamination
of the cosmic shear power spectrum. Assuming that the alignments can be
explained by linear alignment with the smoothed local density field, we find
that a measurement of \sigma_8 in a blue-galaxy dominated, CFHTLS-like survey
would be contaminated by at most +/-0.02 (95% confidence level, SDSS and
WiggleZ) or +/-0.03 (WiggleZ alone) due to intrinsic alignments. [Abridged]Comment: 18 pages, 12 figures, accepted to MNRAS; v2 has correction to one
author's name, NO other changes; v3 has minor changes in explanation and
calculations, no significant difference in results or conclusions; v4 has an
additional footnote about model interpretation, no changes to
data/calculations/result
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