529 research outputs found
Spatial Variations of Galaxy Number Counts in the Sloan Digital Sky Survey. II. Test of Galactic Extinction in High Extinction Regions
Galactic extinction is tested using galaxy number counts at low Galactic
latitude obtained from five band photometry of the Sloan Digital Sky Survey.
The spatial variation of galaxy number counts for low extinction regions of
is consistent with the all-sky reddening map of Schlegel,
Finkbeiner, & Davis (1998) and the standard extinction law. For higher
extinction regions of , however, the map of Schlegel et
al.(1998) overestimates the reddening by a factor up to 1.4, which is likely
ascribed to the departure from proportionality of reddening to infrared
emissivity of dust. This result is consistent with the analysis of Arce &
Goodman (1999) for the Taurus dark cloud complex
Single-epoch supernova classification with deep convolutional neural networks
Supernovae Type-Ia (SNeIa) play a significant role in exploring the history
of the expansion of the Universe, since they are the best-known standard
candles with which we can accurately measure the distance to the objects.
Finding large samples of SNeIa and investigating their detailed characteristics
have become an important issue in cosmology and astronomy. Existing methods
relied on a photometric approach that first measures the luminance of supernova
candidates precisely and then fits the results to a parametric function of
temporal changes in luminance. However, it inevitably requires multi-epoch
observations and complex luminance measurements. In this work, we present a
novel method for classifying SNeIa simply from single-epoch observation images
without any complex measurements, by effectively integrating the
state-of-the-art computer vision methodology into the standard photometric
approach. Our method first builds a convolutional neural network for estimating
the luminance of supernovae from telescope images, and then constructs another
neural network for the classification, where the estimated luminance and
observation dates are used as features for classification. Both of the neural
networks are integrated into a single deep neural network to classify SNeIa
directly from observation images. Experimental results show the effectiveness
of the proposed method and reveal classification performance comparable to
existing photometric methods with multi-epoch observations.Comment: 7 pages, published as a workshop paper in ICDCS2017, in June 201
Delay Time Distribution Measurement of Type Ia Supernovae by the Subaru/XMM-Newton Deep Survey and Implications for the Progenitor
The delay time distribution (DTD) of type Ia supernovae (SNe Ia) from star
formation is an important clue to reveal the still unknown progenitor system of
SNe Ia. Here we report on a measurement of the SN Ia DTD in a delay time range
of t_Ia = 0.1-8.0 Gyr by using the faint variable objects detected in the
Subaru/XMM-Newton Deep Survey (SXDS) down to i' ~ 25.5. We select 65 SN
candidates showing significant spatial offset from nuclei of the host galaxies
having old stellar population at z ~ 0.4-1.2, out of more than 1,000 SXDS
variable objects. Although spectroscopic type classification is not available
for these, we quantitatively demonstrate that more than ~80% of these should be
SNe Ia. The DTD is derived using the stellar age estimates of the old galaxies
based on 9 band photometries from optical to mid-infrared wavelength. Combined
with the observed SN Ia rate in elliptical galaxies at the local universe, the
DTD in t_Ia ~ 0.1-10 Gyr is well described by a featureless power-law as
f_D(t_Ia) \propto t_Ia^{-1}. The derived DTD is in excellent agreement with the
generic prediction of the double-degenerate scenario, giving a strong support
to this scenario. In the single-degenerate (SD) scenario, although predictions
by simple analytic formulations have broad DTD shapes that are similar to the
observation, DTD shapes calculated by more detailed binary population synthesis
tend to have strong peaks at characteristic time scales, which do not fit the
observation. This result thus indicates either that the SD channel is not the
major contributor to SNe Ia in old stellar population, or that improvement of
binary population synthesis theory is required. Various sources of systematic
uncertainties are examined and tested, but our main conclusions are not
affected significantly.Comment: Matches the final version to be published in PASJ. A very minor bug
in the visibility time calculation has been fixed, resulting in slight
changes in the derived DTD (<~ 10%). Conclusions are not affected at all. The
font error of the labels in Fig 3 also fixe
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 ≤ r* ≤ 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 σ fluctuation due to large-scale structure in the galaxy distribution. The shape of the number counts–magnitude relation brighter than r* = 16 is well characterized by N ∝ 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 ± 0.4 × 10^8 L_⊙ h Mpc^(-3), for a reasonably wide range of parameters of the Schechter luminosity function in the B band
Early Science Result from the Japanese Virtual Observatory: AGN and Galaxy Clustering at z = 0.3 to 3.0
We present the result of projected cross correlation analysis of AGNs and
galaxies at redshifts from 0.3 to 3.0. The Japanese Virtual Observatory (JVO)
was used to obtain the Subaru Suprime-Cam images and UKIDSS catalog data around
AGNs. We investigated 1,809 AGNs, which is about ten times larger a sample than
that used in previous studies on AGN-galaxy clustering at redshifts larger than
0.6. 90% of the AGN samples are optically-selected AGN from the SDSS and 2dF
catalogs. The galaxy samples at low redshift includes many redder objects from
UKIDSS survey, while at higher redshift they are mainly blue galaxies from
Suprime-Cam. We found significant excess of galaxies around the AGNs at
redshifts from 0.3 to 1.8. For the low redshift samples (), we obtained
correlation length of 5--6 Mpc (), which
indicates that the AGNs at this redshift range reside in a similar environment
around typical local galaxies. We also found that AGNs at higher redshift
ranges reside in a denser environment than lower redshift AGNs; For AGNs, the cross correlation length was measured as 11
Mpc (). Considering that our galaxies sample is based on
optical observations with Suprime-Cam at the redshift range, it is expected
that blue star-forming galaxies comprise the majority of objects that are
observed to be clustered around the AGNs. It is successfully demonstrated that
the use of the archive through the Virtual Observatory system can provide a
powerful tool for investigating the small scale environment of the intermediate
redshift AGNs.Comment: accepted to PASJ, 36 pages, 21 figures, this is an accepted versio
Proper motions with Subaru II. A sample in the Subaru/XMM-Newton Deep Survey field
We search for stars with proper motions in a set of deep Subaru images,
covering about 0.48 square degrees to a depth of , taken over a
span of five and a half years. We follow the methods described in
\citet{Richmond2009} to reduce and analyze this dataset. We present a sample of
69 stars with motions of high significance, and discuss briefly the populations
from which they are likely drawn. Based on photometry and motions alone, we
expect that 14 of the candidates may be white dwarfs. Our candidate with the
largest proper motion is surprisingly faint and likely to prove interesting:
its colors and motions suggest that it might be an M dwarf moving at over 500
km/sec or an L dwarf in the halo.Comment: 10 pages, 5 figures. Accepted by Publications of the Astronomical
Society of Japan, to appear in volume 62, February 2010. Revised version:
removed PASJ LaTeX tutorial which was mistakenly appended to pape
Hydraulic Performance of the Seepage Collection Ditches at the Albian Sands Muskeg River Mine
The tailings pond at the Muskeg River Mine is a large structure with a 11 km-long ring dyke that contains process affected water (PAW) and tailings sand. The dyke is made of permeable tailings sand and therefore it is equipped with seepage collection ditches that are designed to collect water from drains in the dyke but also to intercept seepage water not collected by the drains and transmit it to the seepage pond for recycling. The effectiveness of this seepage collection system was examined at the downgradient end of the tailings pond (Study Area) where near-surface permeable sand is present. Piezometric level measurements were performed and water samples were collected from a network of 21 piezometers and drive points, and at several other critical locations. Concentrations of major chemical tracers of PAW such as naphthenic acids (NAs) show signs of migration of PAW in the permeable sand deposit, beyond the dyke. This interpretation is supported by stable O and H isotope analysis of water. The interpretation of the piezometric and chemical data revealed that the PAW has migrated past the Inner Ditch but not beyond the Outer Ditch. Elevated hydraulic heads beyond the Outer Ditch prevented further migration. Groundwater locally converges and discharges as surface water in the wet area between the two ditches. Thus, the collection ditch system is currently working effectively to contain PAW. Numerical modeling of the Study Area was able to reasonably recreate the observed hydraulic conditions. Based on these simulations, it is possible that PAW may be migrating through a permeable layer of sand under the bottom of the dyke and pond, and eventually discharging into the wet area between the ditches. The estimated amount of PAW seepage discharged into the wet area is small compared to the total dyke drainage collected by the ditches. These conditions described above, however, may change with the progress of the current dyke expansion work. The wet area between the ditches will be buried and the local hydraulic condition is expected to alter. This may reverse the hydraulic gradient across the Outer Ditch and perhaps will facilitate migration of PAW beyond the Outer Ditch. It is recommended that the following key chemical parameters be used in future groundwater quality monitoring efforts to track PAW migration at the Muskeg River Mine: Na+ Cl- , SO42- , and Ca2+ ions, stable isotopes of hydrogen and oxygen, and Naphthenic acids (NAs.
Proper motions with Subaru I. Methods and a first sample in the Subaru Deep Field
We search for stars with proper motions in a set of twenty deep Subaru
images, covering about 0.28 square degrees to a depth of i ~ 25, taken over a
span of six years. In this paper, we describe in detail our reduction and
techniques to identify moving objects. We present a first sample of 99 stars
with motions of high significance, and discuss briefly the populations from
which they are likely drawn. Based on photometry and motions alone, we expect
that 9 of the candidates may be white dwarfs. We also find a group of stars
which may be extremely metal-poor subdwarfs in the halo.Comment: 12 pages, 8 figures, submitted to PAS
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