900 research outputs found
Galaxy Number Counts from the Sloan Digital Sky Survey Commissioning Data
We present bright galaxy number counts in five broad bands (u', g', r', i', z') from imaging data taken during the commissioning phase of the Sloan Digital Sky Survey (SDSS). The counts are derived from two independent stripes of imaging scans along the celestial equator, one each toward the northern and the southern Galactic cap, covering about 230 and 210 deg^2, respectively. A careful study is made to verify the reliability of the photometric catalog. For galaxies brighter than r* = 16, the catalog produced by automated software is examined against eye inspection of all objects. Statistically meaningful results on the galaxy counts are obtained in the magnitude range 12 ā¤ r* ā¤ 21, using a sample of 900,000 galaxies. The counts from the two stripes differ by about 30% at magnitudes brighter than r* = 15.5, consistent with a local 2 Ļ fluctuation due to large-scale structure in the galaxy distribution. The shape of the number countsāmagnitude relation brighter than r* = 16 is well characterized by N ā 10^(0.6m), the relation expected for a homogeneous galaxy distribution in a "Euclidean" universe. In the magnitude range 16 < r* < 21, the galaxy counts from both stripes agree very well and follow the prediction of the no-evolution model, although the data do not exclude a small amount of evolution. We use empirically determined color transformations to derive the galaxy number counts in the B and I_(814) bands. We compute the luminosity density of the universe at zero redshift in the five SDSS bands and in the B band. We find L_B = 2.4 Ā± 0.4 Ć 10^8 L_ā h Mpc^(-3), for a reasonably wide range of parameters of the Schechter luminosity function in the B band
GABAA Receptor Ī²3 Subunit Expression Regulates Tonic Current in Developing Striatopallidal Medium Spiny Neurons
The striatum is a key structure for movement control, but the mechanisms that dictate the output of distinct subpopulations of medium spiny projection neurons (MSNs), striatonigral projecting and dopamine D1 receptor- (D1+) or striatopallidal projecting and dopamine D2 receptor- (D2+) expressing neurons, remains poorly understood. GABA-mediated tonic inhibition largely controls neuronal excitability and action potential firing rates, and we previously suggested with pharmacological analysis that the GABAA receptor Ī²3 subunit plays a large role in the basal tonic current seen in D2+ MSNs from young mice (Ade et al., 2008; Janssen et al., 2009). In this study, we demonstrated the essential role of the Ī²3 GABAA receptor subunit in mediating MSN tonic currents using conditional Ī²3 subunit knock-out (Ī²3f/fDrd2) mice. Cre-lox genetics were used to generate mice where Cre recombinase was expressed under the D2 receptor (Drd2) promoter. We show that while the wild-type MSN tonic current pattern demonstrates a high degree of variability, tonic current patterns from Ī²3f/fDrd2 mice are narrow, suggesting that the Ī²3 subunit is essential to striatal MSN GABA-mediated tonic current. Our data also suggest that a distinct population of synaptic receptors upregulate due to Ī²3 subunit removal. Further, deletion of this subunit significantly decreases the D2+ MSN excitability. These results offer insight for target mechanisms in Parkinsonās disease, where symptoms arise due to the imbalance in striatal D1+ and D2+ MSN excitability and output
Galaxy Number Counts from the Sloan Digital Sky Survey Commissioning Data
We present bright galaxy number counts in five broad bands (u', g', r', i', z') from imaging data taken during the commissioning phase of the Sloan Digital Sky Survey (SDSS). The counts are derived from two independent stripes of imaging scans along the celestial equator, one each toward the northern and the southern Galactic cap, covering about 230 and 210 deg^2, respectively. A careful study is made to verify the reliability of the photometric catalog. For galaxies brighter than r* = 16, the catalog produced by automated software is examined against eye inspection of all objects. Statistically meaningful results on the galaxy counts are obtained in the magnitude range 12 ā¤ r* ā¤ 21, using a sample of 900,000 galaxies. The counts from the two stripes differ by about 30% at magnitudes brighter than r* = 15.5, consistent with a local 2 Ļ fluctuation due to large-scale structure in the galaxy distribution. The shape of the number countsāmagnitude relation brighter than r* = 16 is well characterized by N ā 10^(0.6m), the relation expected for a homogeneous galaxy distribution in a "Euclidean" universe. In the magnitude range 16 < r* < 21, the galaxy counts from both stripes agree very well and follow the prediction of the no-evolution model, although the data do not exclude a small amount of evolution. We use empirically determined color transformations to derive the galaxy number counts in the B and I_(814) bands. We compute the luminosity density of the universe at zero redshift in the five SDSS bands and in the B band. We find L_B = 2.4 Ā± 0.4 Ć 10^8 L_ā h Mpc^(-3), for a reasonably wide range of parameters of the Schechter luminosity function in the B band
A Catalogue of Morphologically Classified Galaxies from the Sloan Digital Sky Survey: North Equatorial Region
We present a catalogue of morphologically classified bright galaxies in the
north equatorial stripe (230 deg) derived from the Third Data Release of
the Sloan Digital Sky Survey (SDSS). Morphological classification is performed
by visual inspection of images in the band. The catalogue contains 2253
galaxies complete to a magnitude limit of after Galactic extinction
correction, selected from 2658 objects that are judged as extended in the
photometric catalogue in the same magnitude limit. 1866 galaxies in our
catalogue have spectroscopic information. A brief statistical analysis is
presented for the frequency of morphological types and mean colours in the
catalogue. A visual inspection of the images reveals that the rate of
interacting galaxies in the local Universe is approximately 1.5% in the
sample. A verification is made for the photometric catalogue generated
by the SDSS, especially as to its bright end completeness.Comment: Accepted for publication in Astronomical Journal. Table 2 available
at http://www.icrr.u-tokyo.ac.jp/~fukugita/MCGpaper/table2.tx
Lithium and aluminium carbamato derivatives of the utility amide 2, 2, 6, 6- tetramethylpiperidide
Insertion of CO2 into the metal-N bond of a series of synthetically-important alkali-metal TMP (2,2,6,6-tetramethylpiperidide) complexes has been studied. Determined by X-ray crystallography, the molecular structure of the TMEDA-solvated Li derivative shows a central 8-membered (LiOCO)2 ring lying in a chair conformation with distorted tetrahedral lithium centres. While trying to obtain crystals of a THF solvated derivative, a mixed carbonato/carbamato dodecanuclear lithium cluster was formed containing two central (CO3)2- fragments and eight O2CTMP ligands with four distinct bonding modes. A bisalkylaluminium carbamato complex has also been prepared via two different methods (CO2 insertion into a pre-formed Al-N bond and ligand transfer from the corresponding lithium reagent) which adopts a dimeric structure in the solid state
The stellar halo of isolated central galaxies in the Hyper Suprime-Cam imaging survey
We study the faint stellar halo of isolated central galaxies, by stacking
galaxy images in the HSC survey and accounting for the residual sky background
sampled with random points. The surface brightness profiles in HSC -band are
measured for a wide range of galaxy stellar masses
() and out to 120 kpc. Failing to account for
the stellar halo below the noise level of individual images will lead to
underestimates of the total luminosity by . Splitting galaxies
according to the concentration parameter of their light distributions, we find
that the surface brightness profiles of low concentration galaxies drop faster
between 20 and 100 kpc than those of high concentration galaxies. Albeit the
large galaxy-to-galaxy scatter, we find a strong self-similarity of the stellar
halo profiles. They show unified forms once the projected distance is scaled by
the halo virial radius. The colour of galaxies is redder in the centre and
bluer outside, with high concentration galaxies having redder and more
flattened colour profiles. There are indications of a colour minimum, beyond
which the colour of the outer stellar halo turns red again. This colour
minimum, however, is very sensitive to the completeness in masking satellite
galaxies. We also examine the effect of the extended PSF in the measurement of
the stellar halo, which is particularly important for low mass or low
concentration galaxies. The PSF-corrected surface brightness profile can be
measured down to 31 at 3-
significance. PSF also slightly flattens the measured colour profiles.Comment: accepted by MNRAS - Significant changes have been made compared with
the first version, including discussions on the extended PSF wings,
robustness of our results to source detection and masking thresholds and more
detailed investigations on the indications of positive colour gradient
The Blue Tip of the Stellar Locus: Measuring Reddening with the SDSS
We present measurements of reddening due to dust using the colors of stars in
the Sloan Digital Sky Survey (SDSS). We measure the color of main sequence
turn-off stars by finding the "blue tip" of the stellar locus: the prominent
blue edge in the distribution of stellar colors. The method is sensitive to
color changes of order 18, 12, 7, and 8 mmag of reddening in the colors u-g,
g-r, r-i, and i-z, respectively, in regions measuring 90' by 14'. We present
maps of the blue tip colors in each of these bands over the entire SDSS
footprint, including the new dusty southern Galactic cap data provided by the
SDSS-III. The results disfavor the best fit O'Donnell (1994) and Cardelli et
al. (1989) reddening laws, but are well described by a Fitzpatrick (1999)
reddening law with R_V = 3.1. The SFD dust map is found to trace the dust well,
but overestimates reddening by factors of 1.4, 1.0, 1.2, and 1.4 in u-g, g-r,
r-i, and i-z, largely due to the adopted reddening law. In select dusty regions
of the sky, we find evidence for problems in the SFD temperature correction. A
dust map normalization difference of 15% between the Galactic north and south
sky may be due to these dust temperature errors.Comment: 18 pages, 22 figure
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