Luminosity Functions and Point Source Properties from Multiple Chandra Observations of M81

Abstract

We present an analysis of 15 Chandra observations of the nearby spiral galaxy M81 taken over the course of six weeks in May--July 2005. Each observation reaches a sensitivity of ~10^37 erg/s. With these observations and one previous deeper Chandra observation, we compile a master source list of 265 point sources, extract and fit their spectra, and differentiate basic populations of sources through their colors. We also carry out variability analyses of individual point sources and of X-ray luminosity functions in multiple regions of M81 on timescales of days, months, and years. We find that, despite measuring significant variability in a considerable fraction of sources, snapshot observations provide a consistent determination of the X-ray luminosity function of M81. We also fit the X-ray luminosity functions for multiple regions of M81 and, using common parametrizations, compare these luminosity functions to those of two other spiral galaxies, M31 and the Milky Way.

20 pages, 11 figures to be published in ApJ

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• Massive Compact Galaxies with High-Velocity Outflows: Morphological Analysis and Constraints on AGN Activity
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• Deep Chandra Monitoring Observations of NGC 4278: Catalog of Source Properties
• The radial metallicity gradient and the history of elemental enrichment in M81 through emission-line probes
• Chandra ACIS Survey of X-ray Point Sources in Nearby Galaxies. II. X-ray Luminosity Functions and Ultraluminous X-ray Sources
• Deep Chandra Monitoring Observations of NGC 4649: I. Catalog of Source Properties
• Probing the X-Ray Binary Populations of the Ring Galaxy NGC 1291
• Black Holes and Neutron Stars in Nearby Galaxies: Insights from NuSTAR
• Searching for Exoplanets Around X-Ray Binaries with Accreting White Dwarfs, Neutron Stars, and Black Holes
• Optical Spectroscopy of Supernova Remnants in M81 and M82
• A Very Large Array Search for Intermediate-Mass Black Holes in Globular Clusters in M81
• A Multi-epoch X-ray Study of the Spiral Galaxy NGC 7331
• The X-ray variation of M81* resolved by Chandra and NuSTAR
• A deeper look at the X-ray point source population of NGC 4472
• From Blackbirds to Black Holes: Investigating Capture-Recapture Methods for Time Domain Astronomy
• An Energetic Hot Wind from the Low-luminosity Active Galactic Nucleus M81*