Deep Chandra image in the Boötes Field

Junxian Wang

Johns Hopkins University

172 ks Chandra exposure on LALA Boötes field

• One of the deepest Chandra exposures on extra galactic sky, only 2 Ms CDF-N and 1 Ms CDF-S are substantially deeper

174 ks Chandra exposure on LALA Cetus field

• 350 X-ray sources detected (346 in 1 Ms CDF-S, 503 in 2 Ms CDF-N), mostly are extragalactic sources harboring super massive black holes.

• With NDWFS Bw, R, I, and LALA V, z‘ band images, optical counterparts have been found for 90% of the X-ray sources in the Boötes field.

• Around 10 R and bluer bands nondetected sources with soft X-ray colors are candidate z >5 AGNs.

• Spectroscopic identifications are on-going

• Resolves >70% of 2-10 keV background

• Variation in X-ray source count, due to large scale structure

• Wang et al. 2004, AJ

Deep Chandra imaging on high redshift Ly emitters

Large equivalent widths of LALA Ly emitters

• Median EW ~ 240Å (Malhotra & Rhoads 2002)

• stellar populations are expected to produce peak equivalent widths 100Å< EWmax<200Å (Charlot & Fall 1993).

• Stellar populations with high proportions of young, massive stars (Malhotra &Rhoads 2002) can explain the larger equivalent widths.

• The high EWs can also be reproduced by active galactic nuclei, most likely type 2 AGNs,

• The broad-lined (type I) AGNs are ruled out because we see no evidence of broad emission lines from either narrow-band imaging or spectroscopy.

• Ly line luminosities comparable to those of Type II QSOs

• Would be Chandra detectable if they are similar type II QSOs

• None of 101 imaged Ly emitters were detected in X-ray individually

• Or in stacked images with effective exposure time of 11.2 Ms

• Left: all Ly emitters

• Right: Ly emitter with Ly EW > 240Å

Lyman-α to X-ray ratios• Individual Lym

an-α emitters are consistent with some but not all Type-II QSOs.

• The composite Ly-α to X-ray ratio strongly rules out a large fraction of AGN in the Ly-α sample.

Figure from Wang et al 2004, ApJ Letter

Keck/LRIS spectrum of LALA “Boomer”

Conclusion

• None of 101 Ly emitters were detected in X-ray

• <4.8% of them could be AGNs based on their average Ly to X-ray flux ratio.

• No evidence of AGN feature was detected in the optical spectra either (Dawson et al.)

Collaborators

• Sangeeta Malhotra, James Rhoads (STScI)• Michael Brown, Arjun Dey, Buell Jannuzi (NOAO)• Steve Dawson, Hy Spinrad (UC Berkeley)• Timothy Heckman, Colin Norman (JHU)• Daniel Stern (CalTech)• Glenn Tiede (BGSU)• Paolo Tozzi (INAF)