arXiv subjects

J. Ward Moody

Publications and source records attributed to J. Ward Moody.

4 recordsLinked to original sources

arXiv2016

The Effect of Nearby Voids on Galaxy Number Counts

The size, shape and degree of emptiness of void interiors sheds light on the details of galaxy formation. A particularly interesting question is whether void interiors are completely empty or contain a dwarf population. However the nearby voids that are most conducive for dwarf searches have large angular diameters, on the order of a steradian, making it difficult to redshift-map a statistically significant portion of their volume to the magnitude limit of dwarf galaxies. As part of addressing this problem, we investigate here the usefulness of number counts in establishing the best locations to search inside nearby (d < 300 Mpc) galaxy voids, utilizing Wolf plots of log(n < m) vs. m as the basic diagnostic. To illustrate expected signatures, we consider the signature of three void profiles, "cut out", "built up", and "universal profile" carved into Monte-Carlo Schechter function models. We then investigate the signatures of voids in the Millennium Run dark matter simulation and the Sloan Digital Sky Survey. We find in all of these the evidence for cut-out and built-up voids is most discernible when the void diameter is similar to the distance to its center. However the density distribution of the universal profile that is characteristic of actual voids is essentially undetectable at any distance. A useful corollary of this finding is that galaxy counts are a reliable measure of survey completeness and stellar contamination even when sampling through significant voids.

astro-ph.IM↗

arXiv2013

The Stability of BVRI Comparison Stars Near Selected TeV Blazars

We have measured Johnson BV and Cousins RI magnitudes for comparison stars near five TeV blazars. We compare our values with published values, spanning 25 years in some cases, to identify those stars that are most likely proven stable. To avoid zero-point offsets mimicking long-term variability, we based our analysis on the standard deviation between measurements after a mean offset between data sets was removed. We found most stars to be stable at the 0.04 magnitude level. We confirm two stars as variable and identify two others as possibly being variable. In each of the five fields there are at least two stars, and typically many more, that show no evidence of variability.

astro-ph.SR↗

arXiv2005

The KPNO International Spectroscopic Survey. V. H-alpha-selected Survey List 3

The KPNO International Spectroscopic Survey (KISS) is an objective-prism survey designed to detect extragalactic emission-line objects. It combines many of the features of previous slitless spectroscopic surveys with the advantages of modern CCD detectors, and is the first purely digital objective-prism survey for emission-line galaxies (ELGs). Here we present the third list of ELG candidates selected from our red spectral data, which cover the wavelength range 6400 to 7200 A. In most cases, the detected emission line is H-alpha. The current survey list covers the region of the NOAO Deep Wide-Field Survey (NDWFS). This survey covers two fields; the first is 3 x 3 degrees square and located at RA = 14h 30m, DEC = 34.5 deg (B1950), the second is 2.3 x 4.0 degrees and centered at RA = 2h 7.5m, DEC = -4.75 deg. A total area of 19.65 deg^2 is covered by the KISS data. A total of 261 candidate emission-line objects have been selected for inclusion in the survey list (13.3 per deg^2). We tabulate accurate coordinates and photometry for each source, as well as estimates of the redshift, emission-line flux and line equivalent width based on measurements of the digital objective-prism spectra. The properties of the KISS ELGs are examined using the available observational data. When combined with the wealth of multi-wavelength data already available for the NDWFS fields, the current list of KISS ELGs should provide a valuable tool for studying star-formation and nuclear activity in galaxies in the local universe.

astro-ph↗

arXiv2001

The KPNO International Spectroscopic Survey. III. [O III]-selected Survey List

The KPNO International Spectroscopic Survey (KISS) is an objective-prism survey for extragalactic emission-line objects. It combines many of the features of previous slitless spectroscopic surveys with the advantages of modern CCD detectors, and is the first purely digital objective-prism survey for emission-line galaxies. Here we present the first list of emission-line galaxy candidates selected from our blue spectral data, which cover the wavelength range 4800 -- 5500 A. In most cases, the detected emission line is [O III]5007. The current survey list covers a one-degree-wide strip located at Dec = 29 deg 30' (B1950.0) and spanning the right ascension range 8h 30m to 17h 0m. An area of 116.6 deg^2 is covered. A total of 223 candidate emission-line objects have been selected for inclusion in the survey list (1.91 deg^-2). We tabulate accurate coordinates and photometry for each source, as well as estimates of the redshift, emission-line flux, and equivalent width based on measurements of the digital objective-prism spectra. The median apparent magnitude of the sample is B = 18.2, and galaxies with redshifts approaching z = 0.1 are detected. The properties of the KISS emission-line galaxies are examined using the available observational data, and compared to previous surveys carried out with photographic plates as well as with the H-alpha-selected portion of KISS.

astro-ph↗