PROBING THE BALANCE OF AGN AND STAR-FORMING ACTIVITY IN THE LOCAL UNIVERSE WITH ChaMP

Journal Article · Tue Nov 10 00:00:00 EST 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/705/2/1336· OSTI ID:21378335

Constantin, Anca; Green, Paul; Aldcroft, Tom; Kim, Dong-Woo ^[1]; Haggard, Daryl; Anderson, Scott F ^[2]; Barkhouse, Wayne ^[3]

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1. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)
2. Department of Astronomy, University of Washington, Seattle, WA (United States)
3. Department of Physics and Astrophysics, University of North Dakota, Grand Forks, ND 58202 (United States)

The combination of the Sloan Digital Sky Survey (SDSS) and the Chandra Multiwavelength Project (ChaMP) currently offers the largest and most homogeneously selected sample of nearby galaxies for investigating the relation between X-ray nuclear emission, nebular line emission, black hole masses, and properties of the associated stellar populations. We provide X-ray spectral fits and valid uncertainties for all the galaxies with counts ranging from 2 to 1325 (mean 76, median 19). We present here novel constraints that both X-ray luminosity L{sub X} and X-ray spectral energy distribution bring to the galaxy evolutionary sequence H II -> Seyfert/Transition Object -> LINER -> Passive suggested by optical data. In particular, we show that both L{sub X} and GAMMA, the slope of the power law that best fits the 0.5-8 keV spectra, are consistent with a clear decline in the accretion power along the sequence, corresponding to a softening of their spectra. This implies that, at z approx 0, or at low-luminosity active galactic nucleus (AGN) levels, there is an anticorrelation between GAMMA and L/L {sub edd}, opposite to the trend exhibited by high z AGN (quasars). The turning point in the GAMMA-L/L{sub edd} LLAGN + quasars relation occurs near GAMMA approx 1.5 and L/L{sub edd} approx 0.01. Interestingly, this is identical to what stellar mass X-ray binaries exhibit, indicating that we have probably found the first empirical evidence for an intrinsic switch in the accretion mode, from advection-dominated flows to standard (disk/corona) accretion modes in supermassive black hole accretors, similar to what has been seen and proposed to happen in stellar mass black hole systems. The anticorrelation we find between GAMMA and L/L{sub edd} may instead indicate that stronger accretion correlates with greater absorption. Therefore, the trend for softer spectra toward more luminous, high redshift, and strongly accreting (L/L{sub edd} approx> 0.01) AGNs/quasars could simply be the result of strong selection biases reflected in the dearth of type 2 quasar detections.

• OSTI ID: 21378335
• Journal Information: Astrophysical Journal, Vol. 705, Issue 2; Other Information: DOI: 10.1088/0004-637X/705/2/1336; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABSORPTION
ADVECTION
BLACK HOLES
EMISSION
ENERGY SPECTRA
GALACTIC EVOLUTION
GALAXY NUCLEI
LUMINOSITY
MASS
QUASARS
RED SHIFT
STARS
UNIVERSE
X-RAY GALAXIES
COSMIC RADIO SOURCES
COSMIC RAY SOURCES
COSMIC X-RAY SOURCES
EVOLUTION
GALAXIES
MASS TRANSFER
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
SORPTION
SPECTRA