134 research outputs found
The KX method for producing K-band flux-limited samples of quasars
The longstanding question of the extent to which the quasar population is
affected by dust extinction, within host galaxies or galaxies along the line of
sight, remains open. More generally, the spectral energy distributions of
quasars vary significantly and flux-limited samples defined at different
wavelengths include different quasars. Surveys employing flux measurements at
widely separated wavelengths are necessary to characterise fully the spectral
properties of the quasar population. The availability of panoramic
near-infrared detectors on large telescopes provides the opportunity to
undertake surveys capable of establishing the importance of extinction by dust
on the observed population of quasars. We introduce an efficient method for
selecting K-band, flux-limited samples of quasars, termed ``KX'' by analogy
with the UVX method. This method exploits the difference between the power-law
nature of quasar spectra and the convex spectra of stars: quasars are
relatively brighter than stars at both short wavelengths (the UVX method) and
long wavelengths (the KX method). We consider the feasibility of undertaking a
large-area KX survey for damped Ly-alpha galaxies and gravitational lenses
using the planned UKIRT wide-field near-infrared camera.Comment: 6 pages, 3 figures, to appear in MNRA
Technical Note: Method to correlate whole‐specimen histopathology of radical prostatectomy with diagnostic MR imaging
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134778/1/mp1016.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134778/2/mp1016_am.pd
Detection of Lyman-alpha emission from a DLA galaxy: Possible implications for a luminosity-metallicity relation at z = 2-3
In an ongoing programme to identify a sample of high z DLA galaxies we have
found the long sought for case of a Ly-alpha emitter seen in the centre of a
broad DLA trough. This is the predicted `textbook case' of an intervening DLA
galaxy if DLA galaxies are small, but would not be expected if intervening high
redshift DLA galaxies have large gaseous disks. The Ly-alpha flux is
5.4{+2}{-0.8} * 1e-17 ergs/s/cm2 similar to what has been found in previously
known high z DLA galaxies. The impact parameter is found to be 0.3+-0.3 arcsec.
This is smaller than what was found in previous cases but still consistent with
random sight-lines through absorbers with mean impact parameter ~1 arcsec. Of
the 24 DLAs targeted in the NICMOS imaging survey five have now been identified
as Ly-alpha emitters. The DLA galaxies with detected Ly-alpha emission tend to
have higher interstellar metallicities than those with undetected Ly-alpha
emission. This is plausibly explained as a consequence of a positive
correlation between the Ly-alpha line luminosities of the galaxies and their
metallicities, although the present sample is too small for a definitive
conclusion. The available observations of high-redshift DLA galaxies are also
consistent with a negative correlation between Ly-alpha equivalent widths and
metallicities, as seen in nearby star-forming galaxies and usually attributed
to the preferential absorption of Ly-alpha photons by dust grains.Comment: Accepted for publication in A&A-Letter
Serendipity and the SDSS: Discovery of the Largest Known Planetary Nebula on the Sky
Investigation of spectra from the Sloan Digital Sky Survey reveals the
presence of a region of ionized gas of >2 degrees diameter centered
approximately at alpha = 10^h 37^m delta = -00^o 18' (J2000) (Galactic
coordinates l=248, b=+48). [OIII] 4959,5007 emission is particularly strong and
emission from H-alpha and [NII] 6548,6583 is also detectable over a substantial
area on the sky. The combination of emission line ratios, the close to zero
heliocentric radial velocity and the morphology of the structure are consistent
with an identification as a very nearby planetary nebula. The proximity of the
hot, DO white dwarf PG1034+001 further strengthens this interpretation. The
object is: i) the largest planetary nebula on the sky, ii) certainly closer
than any planetary nebula other than Sh 2--216, iii) the first to be
unambiguously associated with a DO white dwarf. A parallax distance for
PG1034+001 would establish whether the structure is in fact the closest, and
one of the physically largest, planetary nebula known.Comment: 12 pages including 4 figures. ApJ Letters in pres
A SINFONI Integral Field Spectroscopy Survey for Galaxy Counterparts to Damped Lyman-alpha Systems - III. Three Additional Detections
We report three additional SINFONI detections of H-alpha emission line from
quasar absorbers, two of which are new identifications. These were targeted
among a sample of systems with log N(HI)>19.0 and metallicities measured from
high-resolution spectroscopy. The detected galaxies are at impact parameters
ranging from 6 to 12 kpc from the quasar's line-of-sight. We derive star
formation rates (SFR) of a few solar masses per year for the two absorbers at
z_abs~1 and SFR=17 solar masses per year for the DLA at z_abs~2. These three
detections are found among a sample of 16 DLAs and sub-DLAs (5 at z_abs~1 and 7
at z_abs~2). For the remaining undetected galaxies, we derive flux limits
corresponding to SFR<0.1--11.0 solar masses per year depending on redshift of
the absorber and depth of the data. When combined with previous results from
our survey for galaxy counterparts to HI-selected absorbers, we find a higher
probability of detecting systems with higher metallicity as traced by dust-free
[Zn/H] metallicity. We also report a higher detection rate with SINFONI for
host galaxies at z_abs~1 than for systems at z_abs~2. Using the NII/H-alpha
ratio, we can thus compare absorption and emission metallicities in the same
high-redshift objects, more than doubling the number of systems for which such
measures are possible.Comment: 16 pages, 8 figures, accepted for publication in MNRA
Barotropic Rossby waves radiating from tropical instability waves in the Pacific Ocean
Author Posting. © American Meteorological Society, 2011. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 41 (2011): 1160–1181, doi:10.1175/2011JPO4547.1.Tropical instability waves are triggered by instabilities of the equatorial current systems, and their sea level signal, with peak amplitude near 5°N, is one of the most prominent features of the dynamic topography of the tropics. Cross-spectral analysis of satellite altimetry observations shows that there is sea level variability in the Pacific Ocean as far north as Hawaii (i.e., 20°N) that is coherent with the sea level variability near 5°N associated with tropical instability waves. Within the uncertainty of the analysis, this off-equatorial variability obeys the dispersion relation for nondivergent, barotropic Rossby waves over a fairly broad range of periods (26–38 days) and zonal wavelengths (9°–23° of longitude) that are associated with tropical instability waves. The dispersion relation and observed wave properties further suggest that the waves are carrying energy away from the instabilities toward the North Pacific subtropical gyre, which, together with the observed coherence of the sea level signal of the barotropic waves with that of the tropical instability waves, suggests that the barotropic Rossby waves are being radiated from the tropical instability waves. The poleward transport of kinetic energy and westward momentum by these barotropic Rossby waves may influence the circulation in the subtropics.Funding for this research came from WHOI’s
TropicalResearch Initiative, the Charles D. Hollister Fund
for Assistant Scientist Support, the John E. and Anne W.
Sawyer Endowed Fund in Special Support of Scientific
Staff, and Grant OCE-0845150 from the National Science
Foundation
ACCESS: Design and Sub-System Performance
Establishing improved spectrophotometric standards is important for a broad range of missions and is relevant to many astrophysical problems. ACCESS, "Absolute Color Calibration Experiment for Standard Stars", is a series of rocket-borne sub-orbital missions and ground-based experiments designed to enable improvements in the precision of the astrophysical flux scale through the transfer of absolute laboratory detector standards from the National Institute of Standards and Technology (NIST) to a network of stellar standards with a calibration accuracy of 1% and a spectral resolving power of 500 across the 0.35 -1.7 micrometer bandpass
Polycomb Repressive Complex 2 (PRC2) Restricts Hematopoietic Stem Cell Activity
Polycomb group proteins are transcriptional repressors that play a central role in the establishment and maintenance of gene expression patterns during development. Using mice with an N-ethyl-N-nitrosourea (ENU)-induced mutation in Suppressor of Zeste 12 (Suz12), a core component of Polycomb Repressive Complex 2 (PRC2), we show here that loss of Suz12 function enhances hematopoietic stem cell (HSC) activity. In addition to these effects on a wild-type genetic background, mutations in Suz12 are sufficient to ameliorate the stem cell defect and thrombocytopenia present in mice that lack the thrombopoietin receptor (c-Mpl). To investigate the molecular targets of the PRC2 complex in the HSC compartment, we examined changes in global patterns of gene expression in cells deficient in Suz12. We identified a distinct set of genes that are regulated by Suz12 in hematopoietic cells, including eight genes that appear to be highly responsive to PRC2 function within this compartment. These data suggest that PRC2 is required to maintain a specific gene expression pattern in hematopoiesis that is indispensable to normal stem cell function
Curcumin Prevents High Fat Diet Induced Insulin Resistance and Obesity via Attenuating Lipogenesis in Liver and Inflammatory Pathway in Adipocytes
Background: Mechanisms underlying the attenuation of body weight gain and insulin resistance in response to high fat diet (HFD) by the curry compound curcumin need to be further explored. Although the attenuation of the inflammatory pathway is an accepted mechanism, a recent study suggested that curcumin stimulates Wnt signaling pathway and hence suppresses adipogenic differentiation. This is in contrast with the known repressive effect of curcumin on Wnt signaling in other cell lineages. Methodology and Principal Findings: We conducted the examination on low fat diet, or HFD fed C57BL/6J mice with or without curcumin intervention for 28 weeks. Curcumin significantly attenuated the effect of HFD on glucose disposal, body weight/fat gain, as well as the development of insulin resistance. No stimulatory effect on Wnt activation was observed in the mature fat tissue. In addition, curcumin did not stimulate Wnt signaling in vitro in primary rat adipocytes. Furthermore, curcumin inhibited lipogenic gene expression in the liver and blocked the effects of HFD on macrophage infiltration and the inflammatory pathway in the adipose tissue. Conclusions and Significance: We conclude that the beneficial effect of curcumin during HFD consumption is mediated by attenuating lipogenic gene expression in the liver and the inflammatory response in the adipose tissue, in the absence o
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