early results from swift's bat agn survey: xmm follow-up observations for 22 bat agns lisa...
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Early Results from Early Results from SWIFT's BAT AGN SWIFT's BAT AGN
Survey: XMM Follow-up Survey: XMM Follow-up Observations for 22 BAT Observations for 22 BAT
AGNsAGNsLisa WinterLisa Winter (Grad Student at UMD)
Richard Mushotzky (GSFC), Jack Tueller (GSFC), Craig Markwardt (GSFC), Christopher Reynolds (UMD)
SWIFT BAT Survey
• The Swift BAT is an 'all sky' instrument- covering ~20% of the sky at any one time and ~ 50% of the sky each day when not triggering on GRBs
• Sensitive in the 15-150 keV band
• Random nature of GRBs leads to relatively uniform sky coverage for BAT- sensitivity 1-3 mC, angular accuracy ~1.7'
• Extensive follow-up of sources by the two other telescopes on SWIFT (UVOT and XRT) with relatively short exposures
‘Unbiased’ Survey
• All previous AGN surveys were biased (wrt obscuration)
• Much larger sample than HEAO-1 (and Integral)-1st sensitive all sky hard x-ray survey in 28 years !
• BAT data provides first large unbiased sample of host galaxy properties
• Direct comparison with z~1 Chandra and XMM surveys* Distribution of N(H) values* Luminosity function* Log N-Log S
*necessary for modeling x-ray background
SWIFT BAT Survey Compared to Other X-ray
Surveys
Brandt & Hasinger 05
Sy2Sy1
I-mag calculated from 2MASS K-mag assuming K-I = 2
(Ferraras et al. 99)
+1
0-1
Log(FX/FI)
-2
Follow-up Observations
• 22 10 ks XMM observations from 26 proposed sources
• Sources selected: Detected with BAT as a
5 sigma or higher detection
Optical counterpart clearly seen in DSS/2MASS images
No previous X-ray spectrum
X-ray contours from SWIFT’s XRT
X-ray Properties of the Sources
XMM follow-up sources:
- Range of fluxes (FX(0.3-10 keV)) from 1.6x10-12 to 3.0x10-11 erg/s cm2
- 8 “unabsorbed” sources (nH < 1021)
- 14 “absorbed” sources, 5 of which are “Compton thick”Log nH (cm-2)
Compton thick
BAT AGNXMM Follow-up
Log
FX (
10-1
00 k
eV)
Spectral Energy Distributions
• Simultaneous XMM OM data in U, UVW1, UVM2, and UVW2 filters
• In addition to the OM data, nearly all of the sources will have SWIFT UVOT data available.
BA
T 1
0-10
0 ke
V
2-10
keV
0.5-
2 ke
V
XMM OM
Sy2Sy1
Characteristic XMM X-ray Spectra
Unabsorbed
ESO 362-G018
Mkn 352
nH = 1023 cm-2
Fe K eqw = 450 eV
NGC 1142
CGCG 041-020
nH = 1023 cm-2
Compton thickFe K eqw = 260 eV
Fe K-alpha lines and Compton thick sources
•Many of the Compton thick sources in the BAT sample have Fe EW <500 eV •For example Mkn 417 has Fe EW ~70 eV and yet is clearly Compton thick •It is not yet clear what this means
BAT
BAT
BAT + XRT/XMM spectra
• We can check variability between XRT and XMM obs.
0.3 - 2 keV
2 - 10 keV
12 of 20 sources with XRT and XMM spectra are variable by 20%
or more
~ 100 days
ESO 362-G018
Summary
• With XMM and XRT data, we are compiling SEDs for the BAT AGN sample
• With XRT and other (XMM, Chandra, etc.) X-ray observations we are collecting information on source X-ray variability.
• Interesting results: 11/14 absorbed sources show weak soft
emission Compton thick sources with small Fe K
equivalent widths (as low as 70 eV for Mrk 417)