THE X-RAY PROPERTIES OF TYPICAL HIGH-REDSHIFT RADIO-LOUD QUASARS
Accepted in ApJ (arXiv:1106.2557)
Laura Lopez (UCSC)Herman Marshall (MIT)Brendan Miller (UMich)Cristian Vignali (INAF)
Cristian Saez (PSU)Niel Brandt (PSU)Ohad Shemmer (UNT)Laura Chomiuk(CfA)
Highlights of our StudyIn a sample of typical high-redshift (z >~ 4) RLQs:
• Study the X-ray spectral properties: 4 XMM and 2 Chandra (~50 ks) moderate to high quality
observations (total number counts per observation between 100-4000 cnts). These sources were already observed before with short exposure (~5ks) Chandra observations (Bassett et al. 2004; Lopez et al. 2006; Shemmer et al. 2006).
• Seek for evidence of Jets: Two sources (PMN J0235-1805 and PMN J2219-2719) with
Chandra and VLA observations (“Snapshot Candidates”; Lopez et al. 2006).
• Compare spectral properties of high redshift RLQs with those of lower redshift RLQs.
What are we studying?
Our Sample
Highlights of our sample:
• High redshift.
• Good quality X-ray spectra.
• Moderate Radio loudness.
PART I Spectral Analysis
Spectral Analysis Results
• No sign of reflection in our sources.
• <Γ>=1.74 ± 0.11; in accordance to median values of lower redshift RLQ samples (e.g, Reeves & Turner 2000).
• Evidence of absorption in one source (NH ~ 2×1022 cm-2).
• Long term Flux variability in 2 of our sources (PMN J02140-518 and PMN J2219-2719; time scales ~500 days).
Absorption in SDSS J0011+1446
PART IIThe quest of Jets
Evidence of a weak jet in PMN J2219-2719 (1)
Over-density significant ~ 4σ
Evidence of a weak jet in PMN J2219-2719 (2)
X-ray flux jet ~ 2% X-ray flux core
PART IIISeeking for relations and
comparing our sample with lower redshift samples
Gamma vs RL
Anticorrelation between Γ and RL. Significant at the 99.9% confidence level.
Similar dependency is found in lower redshift sources (e.g., Reeves & Turner 2000).
The hardening of the spectra with RL suggest rising jet contribution to the X-ray spectra as a function of RL.Expanded sample with z > 2 RLQs.
Γ-RL relation for low and high redshift sources.
Γ = α + β × log RL
To estimate α and β using the IDL routine from Kelly 2007.
--- Our ex. sample (z > 2)
… Reeves & Turner 2000 (z < 2)Kelly (2007)
Conclusions• The power-law X-ray continua of our targets is consistent with
measurements of lower redshift RLQs.
• Anti-correlation between photon index and radio loudness that is consistent with what has been observed at lower redshifts.
• SDSS J0011+1446 has significant X-ray absorption with a column density NH ~ 2×1022 cm-2
• Likely X-ray jet in the Chandra observation of PMN J2219-2719.
