Browsing by Subject "Photometry"

Now showing 1 - 3 of 3

Do metal-polluted stars of the ZZ ceti instability strip have a distinct asteroseismic signature?
(2015-08) Jumper, Kevin Arthur; Winget, Donald Earl, 1955-; Montgomery, Michael Houston; Sneden, Chris
Cooling DA stars that pass through the ZZ instability strip, a region between temperatures of approximately 12,600 K to 11,100 K, tend to experience the driving of g-mode pulsations near their surface layers. These pulsations cause variations in the luminosities of such stars, leading them to be known as DAVs. A fraction of DAVs also have photospheres contaminated by metals, usually thought to be from the tidally disrupted remnants of planetary systems. The high resolution spectroscopy needed to make definite identifications of these metal lines is relatively demanding, whereas it is simple to obtain photometric data on the pulsation periods of DAV stars. Therefore, if known metal-polluted DAVs (DAZVs) have systematic differences in their photometric data compared to that of DAVs that lack such pollution, photometry could provide an easy way to determine which stars are likely to contain metals in their photospheres in the future. However, we find that the known DAZV population is not large enough to permit its behavior to be distinguished from that of the normal DAV population at the present time, though extremely low-mass white dwarfs may help expand the populations and improve the quality of our fits.
The protostellar content of massive star forming regions
(2007-08) Nordhaus, Miranda Kay; Evans, Neal J.
We present preliminary results of an effort to inventory the protostellar content of 20 massive star-forming regions and automate the process for application to a much larger sample. The sample was chosen from a set of massive cores well-studied in molecular lines and dust continuum. We measure photometry at wavelengths ranging from 1.25 to 8.0 [Greek small letter mu]m from 2MASS and GLIMPSE images. Protostars are clearly detected at wavelengths between 1.25 and 4.5 [Greek small letter mu]m. Longward of 4.5 [Greek small letter mu]m diffuse PAH emission becomes problematic. Currently, we are limited by our ability to discriminate against fore/background stars. Initial efforts to automate the photometry look promising, although further analysis is needed.
The e-MERLIN SuperCLASS legacy survey : photometric redshifts and characteristics of spatially resolved [mu] Jy radio sources
(2020-12-03) Manning, Sinclaire M.; Casey, Caitlin M.
We present optical and near-infrared imaging covering a ~1.53 deg² region in the Super-Cluster Assisted Shear Survey (SuperCLASS) field, which aims to make the first robust weak lensing measurement at radio wavelengths. We derive photometric redshifts for [approximately equal to] 176,000 sources down to i'[subscript AB]~24 and present photometric redshifts for 1.4 GHz e-MERLIN and VLA detected radio sources found in the central 0.26 deg². We compile an initial catalog of 149 radio sources brighter than S₁.₄ > 75 µJy and find their photometric redshifts span 0 < z [subscript phot] <4 with radio luminosities between 10²¹ - 10²⁵ W Hz⁻¹, with medians of = 0.55 and =1.9 x 10²³ W Hz⁻¹ respectively. We find 95% of the µJy radio source sample (141/149) have SEDs best fit by star-forming templates while 5% (8/149) are better fit by AGN. Spectral indices are calculated for sources with radio observations from VLA and GMRT at 325 MHz, with an average spectral slope of α=0.59±0.04. Using the full photometric redshift catalog we construct a density map at the redshift of the known galaxy clusters, z=0.20±0.08. Four of the five clusters are prominently detected at > 7 σ in the density map and we confirm the photometric redshifts are consistent with previously measured spectra from a few galaxies at the cluster centers.