PHOTOMETRIC REDSHIFTS of X-ray selected sources in Stripe 82X region - - PowerPoint PPT Presentation
PHOTOMETRIC REDSHIFTS of X-ray selected sources in Stripe 82X region Tonima T Ananna WHY STRIPE 82? 300 sq deg observed between 80 to 120 times by SDSS Also by UKIDSS, GALEX, VISTA, 2MASS and WISE 31.3 sq deg observed by Archival
Tonima T Ananna
WHY STRIPE 82?
➤
300 sq deg observed between 80 to 120 times by SDSS
➤
Also by UKIDSS, GALEX, VISTA, 2MASS and WISE
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31.3 sq deg observed by Archival Chandra, Archival XMM, XMM AO10 and AO13 - ideal for assigning discrete sources to Xray photons (Lamassa et al 2015)
AO13 AO10 ARCH XMM ARCH Chandra Area 15.6 deg sq 4.6 deg sq 6 deg sq 7.4 deg sq Expos. Time 6-8 Ks 4.56 Ks 17-65 Ks 5.7-71.2 Ks # of sources 2440/ 1820 635/ 410 1438/ 881 785/ 463 # with z-spec 548/ 526 89/84 167/ 153 107/ 101
EACH FIELD AND NUMBER OF SOURCES IN EACH FIELD (LAMASSA ET AL 2015 FIGURE 1):
COLLECTION OF PHOTOMETRY
➤ Coadded SDSS catalog (Jiang et al 2014)
reaches 1.9-2.2 magnitudes deeper
➤ Simple aperture corrected photometry
using Lamassa et al SDSS coordinates
➤ ALLWISE - better astrometry and
photometric sensitivity than ALLSKY - took point source photometry within 1”
➤ GALEX - SEXTRACTOR aperture
photometry within 2”
➤ VISTA and UKIDSS match within 2.0” -
aperture sizes 2.8” and 5.7” - not using 2mass right now
SETTING UP LEPHARE
➤ Filter response curves ➤ Redshifts to try - goes unto 6 in steps of 0.04 ➤ Error weight for each band: 0.2, 0.3 for Galex and Wise, 0.02-0.05 for rest ➤ Absolute magnitude ranges to try: -24 to -8 for nearby sources and -30 to -20 for
QSOs
➤ Some other priors such as fraction of reddening to try on SED libraries
CALCULATING SYSTEMATIC SHIFTS
➤ Chose 500 objects marked regular
galaxies from SDSS stripe 82 region
➤ Matched within 1” with all other
catalogs
➤ Ended up with 278 final sources with no
AGN component
➤ Used to calculate systematic shifts for
extended objects
➤ For point sources - chose regular stars,
but Lephare cannot automatically calculate these systematic shifts for nearby stars, so…
CLASSIFYING OBJECTS
PSF prob ==1 and variability > 0.5?
Yes No
QSOVs EXTNV EXTNV Faint (soft flux < 8E-15) EXTNV Bright (soft flux >= 8E-15)
➤ Variability information from
personal communications with
Nathalie Palanque-Delabrouille
Salvato et al 2011
EXTNV BRIGHT EXTNV FAINT
ALAS!
EXTNV bright
GALMS MAG ABS -24,-8:
HOW TO SOLVE THE CLASSIFICATION PROBLEM?
➤ SDSS psf prob not reliable enough, we are using FWHM from Jiang et al catalog ➤ But we also found that there were variable extended sources ➤ We finally decided to categorize as follows: ➤ EXTNV: variability < 0.5, FWHM in i band > 1” ➤ EXTVAR: variability > 0.5 and FWHM in i band > 1” and point like for all sources
with FWHM < 1”
E X T N V
SLIGHT SYSTEMATIC ISSUE WITH AO13 PS…
➤ Simm et al 2015 showed that for variable sources, single epoch photometry improves
median results for variable sources rather than coadded, so we took outliers from PS AO13:
AO13
CHANDRA
FUTURE PLANS
➤ We still need to work on classifying
EXTVAR properly and having the right library for these sources. Some EXTVAR work better with single epoch photometry, but not all. Explore how to isolate…
➤ Check reliability of counterparts for
Archival XMM and Chandra
➤ Any ideas you may have for
improvements…
Professor Meg Urry