SwiftBAT Survey of AGNs

Abstract

We present the results of the analysis of the first 9 months of data of the Swift BAT survey of AGNs in the 14Y195 keV band. Using archival X-ray data or follow-up Swift XRT observations, we have identified 129 (103 AGNs) of 130 objects detected at jbj > 15 and with significance >4.8 . One source remains unidentified. These same X-ray data have allowed measurement of the X-ray properties of the objects. We fit a power law to the log N Ylog S distribution, and find the slope to be 1:42 AE 0:14. Characterizing the differential luminosity function data as a broken power law, we find a break luminosity log L Ã (erg s À1 ) = 43.85 AE 0.26, a low-luminosity power law slope a ¼ 0:84 þ0:16 À0:22 , and a highluminosity power law slope b ¼ 2:55 þ0:43 À0:30 , similar to the values that have been reported based on INTEGRAL data. We obtain a mean photon index 1.98 in the 14Y195 keV band, with an rms spread of 0.27. Integration of our luminosity function gives a local volume density of AGNs above 10 41 erg s À1 of 2:4 ; 10 À3 Mpc À3 , which is about 10% of the total luminous local galaxy density above M Ã ¼ À19:75. We have obtained X-ray spectra from the literature and from Swift XRT follow-up observations. These show that the distribution of log n H is essentially flat from n H ¼ 10 20 to1024 cm À2 , with 50% of the objects having column densities of less than 10 22 cm À2 . BAT Seyfert galaxies have a median redshift of 0.03, a maximum log luminosity of 45.1, and approximately half have log n H > 22.

Constraints on the local sources of ultra high-energy cosmic rays

“…LUMINOSITY FUNCTION CONSTRAINTS Equation (5) provides the number density of active flares required to account for the observed flux of UHECRs as a function of flare luminosity. Figure 1 compares this result with the cumulative number density of high luminosity AGN at z < 0.2 in the energy bands of 0.5-2 keV (ROSAT, Miyaji et al 2000), 17-60 keV (INTEGRAL, Sazonov et al 2007), 15-195 keV (Swift BAT, Tueller et al 2008), and > 100 MeV (EGRET, Chiang & Mukherjee 1998). At the high luminosities under consideration, all the soft X-ray (0.5-2 keV) sources in the ROSAT survey are identified (including stars and X-ray clusters in addition to AGN), and all but one of the Swift BAT sources are identified 7 .…”

Accurate classification of 17 AGNs detected with Swift/BAT

“…3, From the features above we are able to classify this source for the first time as a Seyfert 2 AGN at redshift z = 0.035 ± 0.001. Our classification is more thorough with respect to that of Tueller et al (2008) who report it as a "galaxy".…”

The evolution of the X-ray luminosity functions of unabsorbed and absorbed AGNs out to z∼ 5

“…In Figure 16 we show our inferred distribution of NH (the NH function) evaluated at z = 0.05 and log LX = 43.5. In the left panel, we compare to estimates of the NH function from U14, based on direct measurements of NH in the Swift/BAT local AGN sample (Tueller et al 2008;Ichikawa et al 2012) and corrected for absorption-dependent biases. Our inferred NH function has a similar overall shape to the U14 measurements, dropping between log NH ∼ 20 − 21 and log NH ∼ 22 − 23 and peaking again at log NH ≈ 23 − 24.…”