arXiv subjects

Michael Werner

Publications and source records attributed to Michael Werner.

40 records · Page 3Linked to original sources

arXiv2006

Spitzer Survey of the Large Magellanic Cloud, Surveying the Agents of a Galaxy's Evolution (SAGE) I: Overview and Initial Results

We are performing a uniform and unbiased, ~7x7 degrees imaging survey of the Large Magellanic Cloud (LMC), using the IRAC and MIPS instruments on board the Spitzer Space Telescope in order to survey the agents of a galaxy's evolution (SAGE), the interstellar medium (ISM) and stars in the LMC. The detection of diffuse ISM with column densities >1.2x10^21 H cm^-2 permits detailed studies of dust processes in the ISM. SAGE's point source sensitivity enables a complete census of newly formed stars with masses >3 solar masses that will determine the current star formation rate in the LMC. SAGE's detection of evolved stars with mass loss rates >1x10^-8 solar masses per year will quantify the rate at which evolved stars inject mass into the ISM of the LMC. The observing strategy includes two epochs in 2005, separated by three months, that both mitigate instrumental artifacts and constrain source variability. The SAGE data are non-proprietary. The data processing includes IRAC and MIPS pipelines and a database for mining the point source catalogs, which will be released to the community in support of Spitzer proposal cycles 4 and 5. We present initial results on the epoch 1 data with a special focus on the N79 and N83 region. The SAGE epoch 1 point source catalog has ~4 million sources. The point source counts are highest for the IRAC 3.6 microns band and decrease dramatically towards longer wavelengths consistent with the fact that stars dominate the point source catalogs and that the dusty objects, e.g. young stellar objects and dusty evolved stars that detected at the longer wavelengths, are rare in comparison. We outline a strategy for identifying foreground MW stars, that may comprise as much as 18% of the source list, and background galaxies, that may comprise ~12% of the source list.

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arXiv2005

A Short and Personal History of the Spitzer Space Telescope

The Spitzer Space Telescope, born as the Shuttle Infrared Telescope Facility (SIRTF) and later the Space Infrared Telescope Facility (still SIRTF), was under discussion and development within NASA and the scientific community for more than 30 years prior to its launch in 2003. This brief history chronicles a few of the highlights and the lowlights of those 30 years from the authors personal perspective. A much more comprehensive history of SIRTF/Spitzer has been written by George Rieke (2006).

astro-ph↗

arXiv2004

Spitzer Space Telescope Observations of the Aftermath of Microlensing Event MACHO-LMC-5

We have carried out photometry of the microlensing event MACHO-LMC-5 with Spitzer's IRAC ten years after the magnification of the LMC source star was recorded. This event is unique in the annals of gravitational microlensing: the lensing star itself has been observed using HST (once with WFPC2 and twice with ACS/HRC). Since the separation between the source and lens at the epoch of the Spitzer observations was $\sim0.24''$, the two stars cannot be resolved in the Spitzer images. However, the IRAC photometry clearly establishes that the lens is a M5 dwarf star from its infrared excess, which in turn yields a mass of $\sim0.2 M_{\odot}$. This demonstrates the potential of Spitzer to detect the lenses in other gravitational microlensing events.

astro-ph↗

arXiv2004

Chandra X-ray observations of Young Clusters I. NGC2264 Data

We present results of a Chandra observation of a field in NGC 2264. The observations were taken with the ACIS-I camera with an exposure time of 48.1 ks. We present a catalog of 263 sources, which includes X-ray luminosity, optical and infrared photometry and X-ray variability information. We found 41 variable sources, 14 of which have a flare-like light curve, and 2 of which have a pattern of a steady increase or decrease over a 10 hour period. The optical and infrared photometry for the stars identified as X-ray sources are consistent with most of these objects being pre-main sequence stars with ages younger than 3 Myr.

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