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Detecting active comets with SDSS

Description: Using a sample of serendipitously discovered active comets in the Sloan Digital Sky Survey (SDSS), we develop well-controlled selection criteria for greatly increasing the efficiency of comet identification in the SDSS catalogs. After follow-up visual inspection of images to reject remaining false positives, the total sample of SDSS comets presented here contains 19 objects, roughly one comet per 10 million other SDSS objects. The good understanding of selection effects allows a study of the population statistics, and we estimate the apparent magnitude distribution to r {approx} 18, the ecliptic latitude distribution, and the comet distribution in SDSS color space. The most surprising results are the extremely narrow range of colors for comets in our sample (e.g. root-mean-square scatter of only {approx}0.06 mag for the g-r color), and the similarity of comet colors to those of jovian Trojans. We discuss the relevance of our results for upcoming deep multi-epoch optical surveys such as the Dark Energy Survey, Pan-STARRS, and the Large Synoptic Survey Telescope (LSST), and estimate that LSST may produce a sample of about 10,000 comets over its 10-year lifetime.
Date: December 1, 2010
Creator: Solontoi, Michael; Ivezic, Zeljko; West, Andrew A.; Claire, Mark; Juric, Mario; Becker, Andrew et al.
Partner: UNT Libraries Government Documents Department

Ensemble Properties of Comets in the Sloan Digital Sky Survey

Description: We present the ensemble properties of 31 comets (27 resolved and 4 unresolved) observed by the Sloan Digital Sky Survey (SDSS). This sample of comets represents about 1 comet per 10 million SDSS photometric objects. Five-band (u, g, r, i, z) photometry is used to determine the comets colors, sizes, surface brightness profiles, and rates of dust production in terms of the Afp formalism. We find that the cumulative luminosity function for the Jupiter Family Comets in our sample is well fit by a power law of the form N(<H) {proportional_to} 10{sup (0.49{+-}0.05)H} for H < 18, with evidence of a much shallower fit N(<H) {proportional_to} 10{sup (0.19{+-}0.03)H} for the faint (14.5 < H < 18) comets. The resolved comets show an extremely narrow distribution of colors (0.57 {+-} 0.05 in g - r for example), which are statistically indistinguishable from that of the Jupiter Trojans. Further, there is no evidence of correlation between color and physical, dynamical, or observational parameters for the observed comets.
Date: February 1, 2012
Creator: Solontoi, Michael; Ivezic, Zeljko; Juric, Mario; Becker, Andrew C.; Jones, Lynne; West, Andrew A. et al.
Partner: UNT Libraries Government Documents Department

HEP Science Network Requirements--Final Report

Description: The Energy Sciences Network (ESnet) is the primary provider of network connectivity for the US Department of Energy Office of Science, the single largest supporter of basic research in the physical sciences in the United States. In support of the Office of Science programs, ESnet regularly updates and refreshes its understanding of the networking requirements of the instruments, facilities, scientists, and science programs that it serves. This focus has helped ESnet to be a highly successful enabler of scientific discovery for over 20 years. In August 2009 ESnet and the Office of High Energy Physics (HEP), of the DOE Office of Science, organized a workshop to characterize the networking requirements of the programs funded by HEP. The International HEP community has been a leader in data intensive science from the beginning. HEP data sets have historically been the largest of all scientific data sets, and the communty of interest the most distributed. The HEP community was also the first to embrace Grid technologies. The requirements identified at the workshop are summarized below, and described in more detail in the case studies and the Findings section: (1) There will be more LHC Tier-3 sites than orginally thought, and likely more Tier-2 to Tier-2 traffic than was envisioned. It it not yet known what the impact of this will be on ESnet, but we will need to keep an eye on this traffic. (2) The LHC Tier-1 sites (BNL and FNAL) predict the need for 40-50 Gbps of data movement capacity in 2-5 years, and 100-200 Gbps in 5-10 years for HEP program related traffic. Other key HEP sites include LHC Tier-2 and Tier-3 sites, many of which are located at universities. To support the LHC, ESnet must continue its collaborations with university and international networks. (3) While in all cases the ...
Date: April 27, 2010
Creator: Bakken, Jon; Barczyk, Artur; Blatecky, Alan; Boehnlein, Amber; Carlson, Rich; Chekanov, Sergei et al.
Partner: UNT Libraries Government Documents Department

Exploring the Variable Sky with the Sloan Digital Sky Survey

Description: We quantify the variability of faint unresolved optical sources using a catalog based on multiple SDSS imaging observations. The catalog covers SDSS Stripe 82, which lies along the celestial equator in the Southern Galactic Hemisphere (22h 24m < {alpha}{sub J2000} < 04h 08m, -1.27{sup o} < {delta}{sub J2000} < +1.27{sup o}, {approx} 290 deg{sup 2}), and contains 58 million photometric observations in the SDSS ugriz system for 1.4 million unresolved sources that were observed at least 4 times in each of the gri bands (with a median of 10 observations obtained over {approx}5 years). In each photometric bandpass we compute various low-order lightcurve statistics such as root-mean-square scatter (rms), {chi}{sup 2} per degree of freedom, skewness, minimum and maximum magnitude, and use them to select and study variable sources. We find that 2% of unresolved optical sources brighter than g = 20.5 appear variable at the 0.05 mag level (rms) simultaneously in the g and r bands. The majority (2/3) of these variable sources are low-redshift (< 2) quasars, although they represent only 2% of all sources in the adopted flux-limited sample. We find that at least 90% of quasars are variable at the 0.03 mag level (rms) and confirm that variability is as good a method for finding low-redshift quasars as is the UV excess color selection (at high Galactic latitudes). We analyze the distribution of lightcurve skewness for quasars and find that is centered on zero. We find that about 1/4 of the variable stars are RR Lyrae stars, and that only 0.5% of stars from the main stellar locus are variable at the 0.05 mag level. The distribution of lightcurve skewness in the g-r vs. u-g color-color diagram on the main stellar locus is found to be bimodal (with one mode consistent with Algol-like behavior). Using over ...
Date: April 1, 2007
Creator: Sesar, Branimir; Ivezic, Zeljko; Lupton, Robert; Juric, Mario; Gunn, James; Knapp, Gillian et al.
Partner: UNT Libraries Government Documents Department