44 research outputs found
Determination of Galaxy Spin Vectors in the Pisces-Perseus Supercluster with the Arecibo Telescope
We use HI observations made with the upgraded Arecibo 305M Telescope in
August 1998 to obtain accurate spin vector determinations for 54 nearly edge-on
galaxies in the Minnesota Automated Plate Scanner Pisces-Perseus Survey
(MAPS-PP). We introduce a simple observational technique of determining the
sense of rotation for galaxies, even when their HI disks are not fully
resolved. We examined the spin vector distribution of these 54 galaxies for
evidence of preferential galaxy alignments. We use the Kuiper statistic, a
variant of the Kolmogorov--Smirnov statistic, to determine the significance of
any anisotropies in the distribution of galaxy spin vectors. The possibility of
``spin vector domains'' is also investigated. We find no significant evidence
of preferential galaxy alignments in this sample. However, we show tha t the
small sample size places weak limits on the level of galaxy alignments.Comment: 22 pages, 7 figures, Accepted for Publication in Astronomical Journa
Galaxies on the Blue Edge
We have successfully constructed a catalog of HI-rich galaxies selected from
the Minnesota Automated Plate Scanner Catalog of the Palomar Observatory Sky
Survey (POSS I) based solely on optical criteria. We identify HI-rich
candidates by selecting the bluest galaxies at a given apparent magnitude,
those galaxies on the "blue edge" of POSS I color-magnitude parameter space.
Subsequent 21-cm observations on the upgraded Arecibo 305m dish detected over
50% of the observed candidates. The detected galaxies are HI-rich with HI
masses comparable to "normal" high surface brightness disk galaxies and they
have gas mass-to-light ratios ranging from 0.1 to 4.8 (in solar units).
Comparison of our candidate galaxies with known low surface brightness galaxies
(hereafter LSBs) shows that they exhibit similar optical and HI properties to
that population. We also show that previously identified LSBs, including
several LSBs with red B-V colors, preferentially occupy the "blue edge" of POSS
I color-magnitude parameter space. Their presence on the "blue edge" appears to
be a selection effect due to differing plate limits in the two POSS I
bandpasses. This suggests the POSS I is a good filter for separating galaxies
on the higher surface brightness end of the LSB population from the general
population of galaxies in the night sky.Comment: 56 pages, 19 figures, to be published in the Astronomical Journal
(July 1, 2002
The FIRST Bright Quasar Survey. II. 60 Nights and 1200 Spectra Later
We have used the VLA FIRST survey and the APM catalog of the POSS-I plates as
the basis for constructing a new radio-selected sample of optically bright
quasars. This is the first radio-selected sample that is competitive in size
with current optically selected quasar surveys. Using only two basic criteria,
radio-optical positional coincidence and optical morphology, quasars and BL
Lacs can be identified with 60% selection efficiency; the efficiency increases
to 70% for objects fainter than magnitude 17. We show that a more sophisticated
selection scheme can predict with better than 85% reliability which candidates
will turn out to be quasars.
This paper presents the second installment of the FIRST Bright Quasar Survey
with a catalog of 636 quasars distributed over 2682 square degrees. The quasar
sample is characterized and all spectra are displayed. The FBQS detects both
radio-loud and radio-quiet quasars out to a redshift z>3. We find a large
population of objects of intermediate radio-loudness; there is no evidence in
our sample for a bimodal distribution of radio characteristics. The sample
includes ~29 broad absorption line quasars, both high and low ionization, and a
number of new objects with remarkable optical spectra.Comment: 41 pages plus 39 gifs which contain all quasar spectra. Accepted for
publication in the Astrophysical Journal Supplement Serie
The Nearby Supernova Factory
The Nearby Supernova Factory (SNfactory) is an ambitious project to find and
study in detail approximately 300 nearby Type Ia supernovae (SNe~Ia) at
redshifts 0.03<z<0.08. This program will provide an exceptional data set of
well-studied SNe in the nearby smooth Hubble flow that can be used as
calibration for the current and future programs designed to use SNe to measure
the cosmological parameters. The first key ingredient for this program is a
reliable supply of Hubble-flow SNe systematically discovered in unprecedented
numbers using the same techniques as those used in distant SNe searches. In
2002, 35 SNe were found using our test-bed pipeline for automated SN search and
discovery. The pipeline uses images from the asteroid search conducted by the
Near Earth Asteroid Tracking group at JPL. Improvements in our subtraction
techniques and analysis have allowed us to increase our effective SN discovery
rate to ~12 SNe/month in 2003.Comment: 7 pages, 3 figures to be published in New Astronomy Review
Radio-optical scrutiny of compact AGN: Correlations between properties of pc-scale jets and optical nuclear emission
We study the correlations between the Very Long Baseline Array radio emission
at 15 GHz, extended emission at 151 MHz, and optical nuclear emission at 5100
AA for a complete sample of 135 compact jets. We use the partial Kendall's tau
correlation analysis to check the link between radio properties of parsec-scale
jets and optical luminosities of host AGN. We find a significant positive
correlation for 99 quasars between optical nuclear luminosities and total radio
(VLBA) luminosities of unresolved cores at 15 GHz originated at milliarcseconds
scales. For 18 BL Lacs, the optical continuum emission correlates with the
radio emission of the jet at 15 GHz. We suggest that the radio and optical
emission are beamed and originate in the innermost part of the
sub--parsec-scale jet in quasars. Analysis of the relation between the apparent
speed of the jet and the optical nuclear luminosity at 5100 AA supports the
relativistic beaming model for the optical emission generated in the jet, and
allows the peak values of the intrinsic optical luminosity of the jet and its
Lorentz factor to be estimated for the populations of quasars, BL Lacs, and
radio galaxies. The radio-loudness of quasars is found to increase at high
redshifts, which can be a result of lower efficiency of the accretion in AGN
having higher radio luminosities. A strong positive correlation is found
between the intrinsic kinetic power of the jet and the apparent luminosities of
the total and the unresolved core emission of the jet at 15 GHz. This
correlation is interpreted in terms of intrinsically more luminous parsec-scale
jet producing more luminous extended structure which is detectable at low radio
frequencies, 151 MHz. A possibility that the low frequency radio emission is
relativistically beamed in superluminal AGN and therefore correlates with radio
luminosity of the jet at 15 GHz can not be ruled out (abridged).Comment: 16 pages, 10 figuers; minor comments are added; accepted to A&
The Activity of the Neighbours of Seyfert Galaxies
We present a follow-up study on a series of papers concerning the role of
close interactions as a possible triggering mechanism of AGN activity. We have
already studied the close (<100kpc/h) and the large scale (<1 Mpc/h)
environment of a local sample of Sy1, Sy2 and bright IRAS galaxies (BIRG) and
their respective control samples. The results led us to the conclusion that a
close encounter appears capable of activating a sequence where an absorption
line galaxy (ALG) galaxy becomes first a starburst, then a Sy2 and finally a
Sy1. Here we investigate the activity of neighboring galaxies of different
types of AGN, since both galaxies of an interacting pair should be affected. To
this end we present the optical spectroscopy and X-ray imaging of 30
neighbouring galaxies around two local (z<0.034) samples of 10 Sy1 and 13 Sy2
galaxies. Based on the optical spectroscopy we find that more than 70% of all
neighbouring galaxies exhibit star forming and/or nuclear activity (namely
recent star formation and/or AGN), while an additional X-ray analysis showed
that this percentage might be significantly higher. Furthermore, we find a
statistically significant correlation, at a 99.9% level, between the value of
the neighbour's [OIII]/H\beta ratio and the activity type of the central active
galaxy, i.e. the neighbours of Sy2 galaxies are systematically more ionized
than the neighbours of Sy1s. This result, in combination with trends found
using the Equivalent Width of the H\alpha emission line and the stellar
population synthesis code STARLIGHT, indicate differences in the stellar mass,
metallicity and star formation history between the samples. Our results point
towards a link between close galaxy interactions and activity and also provide
more clues regarding the possible evolutionary sequence inferred by our
previous studies.Comment: Accepted for publication in A&A. 17 pages, 4 figures. arXiv admin
note: substantial text overlap with arXiv:0910.1355v1 (withdrawn
The 1000 brightest HIPASS galaxies: Newly cataloged galaxies
The H I Parkes All-Sky Survey (HIPASS) is a blind 21 cm survey for extragalactic neutral hydrogen, covering the whole southern sky. The HIPASS Bright Galaxy Catalog (BGC) is a subset of HIPASS and contains the 1000 H I brightest (peak flux density) galaxies. Here we present the 138 HIPASS BGC galaxies that had no redshift measured prior to the Parkes multibeam H I surveys. Of the 138 galaxies, 87 are newly cataloged. Newly cataloged is defined as having no optical ( or infrared) counterpart in the NASA/IPAC Extragalactic Database. Using the Digitized Sky Survey, we identify optical counterparts for almost half of the newly cataloged galaxies, which are typically of irregular or Magellanic morphological type. Several H I sources appear to be associated with compact groups or pairs of galaxies rather than an individual galaxy. The majority ( 57) of the newly cataloged galaxies lie within 10degrees of the Galactic plane and are missing from optical surveys as a result of confusion with stars or dust extinction. This sample also includes newly cataloged galaxies first discovered by Henning et al. in the H I shallow survey of the zone of avoidance. The other 30 newly cataloged galaxies escaped detection because of their low surface brightness or optical compactness. Only one of these, HIPASS J0546-68, has no obvious optical counterpart, as it is obscured by the Large Magellanic Cloud. We find that the newly cataloged galaxies with -b->10degrees are generally lower in H I mass and narrower in velocity width compared with the total HIPASS BGC. In contrast, newly cataloged galaxies behind the Milky Way are found to be statistically similar to the entire HIPASS BGC. In addition to these galaxies, the HIPASS BGC contains four previously unknown H I clouds
Pediatric malignancies presenting as a possible infectious disease
<p>Abstract</p> <p>Background</p> <p>The clinical, laboratory, and radiological features of malignancy can overlap with those of infection. The purpose of this study was to determine the findings in children who were initially thought to have an infectious disease but ultimately proved to have a malignancy.</p> <p>Methods</p> <p>The database of patients diagnosed with a malignancy in the Northern Alberta Children's Cancer Program (NACCP) January 1, 1993 to December 31, 2003 was merged with the database of inpatients referred to the infectious diseases service at the Stollery Children's Hospital and charts were reviewed on all patients referred to the infectious diseases consult service prior to the diagnosis of malignancy.</p> <p>Results</p> <p>An infectious diseases consultation for diagnosis was requested in 21 of 561 patients prior to the confirmation of malignancy, and 3 of these 21 patients had both infection and malignancy (leukemia (N = 13), lymphoma (N = 3), rhabdomyosarcoma (N = 1), Langerhan's cell histiocytosis (N = 1), fibrous histicocytosis (N = 1), ependymoma (N = 1), and neuroblastoma (N = 1). The most common reason for infectious diseases consultation was suspected muskuloskeletal infection (N = 9). A palpable or radiographically enlarged spleen was noted in 11 patients (52%). All but 2 patients had abnormal hematologic parameters while an elevated lactate dehydrogenase (LDH) occurred in 10 patients (48%). Delay of diagnosis because of investigation or therapy for an infectious disease occurred in only 2 patients.</p> <p>Conclusion</p> <p>It is not common for treatment of pediatric malignancies to be delayed because infection is thought to be the primary diagnosis. However, pediatric infectious diseases physicians should consider malignancy in the differential diagnosis when they see patients with fever and bone pain, unexplained splenomegaly or abnormal complete blood cell counts. Other clues may include hepatomegaly or elevated LDH.</p