Chandra observations of the QSO pair Q2345+007

Binary or massive dark lens?

Paul J. Green, Chris Kochanek, Aneta Siemiginowska, Dong Woo Kim, Maxim Markevitch, John Silverman, Anil Dosaj, Buell Tomasson Jannuzi, Chris Smith

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

The components of the wide (7″.3) separation quasar pair Q2345+007A, B (z = 2.15) have the most strikingly similar optical spectra seen to date (Steidel & Sargent) yet no detected lensing mass, making this system the best candidate known for a massive (∼1014 M) dark matter lens system. Here we present results from a 65 ks Chandra observation designed to investigate whether it is a binary quasar or a gravitational lens. We find no X-ray evidence for a lensing cluster to a (0.5-2 keV) flux limit of 2 × 10-15 ergs cm-2 s -1, which is consistent with lensing only for a reduced baryon fraction. Using the Chandra X-ray observations of the quasars themselves, together with new and published optical measurements, we use the observed emission properties of the quasars for further tests between the lens and binary hypotheses. Assuming similar line-of-sight absorption to the images, we find that their X-ray continuum slopes are inconsistent (ΓA = 2.30-0.30+0.36 and ΓB = 0.83 -0.44+0.49) as are their X-ray-to-optical flux ratios. The probability that B suffers intrinsic absorption sufficient to account for these spectral differences is negligible. We present new optical evidence that the flux ratio of the pair is variable, so the time delay in a lens scenario could cause some of the discrepancies. However, adequately large variations in overall spectral energy distribution are rare in individual QSOs. All new evidence here weighs strongly toward the binary interpretation. Q2345+007 thus may represent the highest redshift example known of an interaction-triggered but as-yet unmerged luminous active galactic nucleus.

Original languageEnglish (US)
Pages (from-to)721-732
Number of pages12
JournalAstrophysical Journal
Volume571
Issue number2 I
DOIs
StatePublished - Jun 1 2002
Externally publishedYes

Fingerprint

quasars
lenses
x rays
gravitational lenses
erg
spectral energy distribution
optical measurement
active galactic nuclei
line of sight
optical spectrum
baryons
dark matter
time lag
slopes
continuums
causes
energy
interactions

Keywords

  • Gravitational lensing
  • Quasars: absorption lines
  • X-rays: general

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Green, P. J., Kochanek, C., Siemiginowska, A., Kim, D. W., Markevitch, M., Silverman, J., ... Smith, C. (2002). Chandra observations of the QSO pair Q2345+007: Binary or massive dark lens? Astrophysical Journal, 571(2 I), 721-732. https://doi.org/10.1086/340051

Chandra observations of the QSO pair Q2345+007 : Binary or massive dark lens? / Green, Paul J.; Kochanek, Chris; Siemiginowska, Aneta; Kim, Dong Woo; Markevitch, Maxim; Silverman, John; Dosaj, Anil; Jannuzi, Buell Tomasson; Smith, Chris.

In: Astrophysical Journal, Vol. 571, No. 2 I, 01.06.2002, p. 721-732.

Research output: Contribution to journalArticle

Green, PJ, Kochanek, C, Siemiginowska, A, Kim, DW, Markevitch, M, Silverman, J, Dosaj, A, Jannuzi, BT & Smith, C 2002, 'Chandra observations of the QSO pair Q2345+007: Binary or massive dark lens?', Astrophysical Journal, vol. 571, no. 2 I, pp. 721-732. https://doi.org/10.1086/340051
Green PJ, Kochanek C, Siemiginowska A, Kim DW, Markevitch M, Silverman J et al. Chandra observations of the QSO pair Q2345+007: Binary or massive dark lens? Astrophysical Journal. 2002 Jun 1;571(2 I):721-732. https://doi.org/10.1086/340051
Green, Paul J. ; Kochanek, Chris ; Siemiginowska, Aneta ; Kim, Dong Woo ; Markevitch, Maxim ; Silverman, John ; Dosaj, Anil ; Jannuzi, Buell Tomasson ; Smith, Chris. / Chandra observations of the QSO pair Q2345+007 : Binary or massive dark lens?. In: Astrophysical Journal. 2002 ; Vol. 571, No. 2 I. pp. 721-732.
@article{27d03c76097140058d5df944ee9e1942,
title = "Chandra observations of the QSO pair Q2345+007: Binary or massive dark lens?",
abstract = "The components of the wide (7″.3) separation quasar pair Q2345+007A, B (z = 2.15) have the most strikingly similar optical spectra seen to date (Steidel & Sargent) yet no detected lensing mass, making this system the best candidate known for a massive (∼1014 M⊙) dark matter lens system. Here we present results from a 65 ks Chandra observation designed to investigate whether it is a binary quasar or a gravitational lens. We find no X-ray evidence for a lensing cluster to a (0.5-2 keV) flux limit of 2 × 10-15 ergs cm-2 s -1, which is consistent with lensing only for a reduced baryon fraction. Using the Chandra X-ray observations of the quasars themselves, together with new and published optical measurements, we use the observed emission properties of the quasars for further tests between the lens and binary hypotheses. Assuming similar line-of-sight absorption to the images, we find that their X-ray continuum slopes are inconsistent (ΓA = 2.30-0.30+0.36 and ΓB = 0.83 -0.44+0.49) as are their X-ray-to-optical flux ratios. The probability that B suffers intrinsic absorption sufficient to account for these spectral differences is negligible. We present new optical evidence that the flux ratio of the pair is variable, so the time delay in a lens scenario could cause some of the discrepancies. However, adequately large variations in overall spectral energy distribution are rare in individual QSOs. All new evidence here weighs strongly toward the binary interpretation. Q2345+007 thus may represent the highest redshift example known of an interaction-triggered but as-yet unmerged luminous active galactic nucleus.",
keywords = "Gravitational lensing, Quasars: absorption lines, X-rays: general",
author = "Green, {Paul J.} and Chris Kochanek and Aneta Siemiginowska and Kim, {Dong Woo} and Maxim Markevitch and John Silverman and Anil Dosaj and Jannuzi, {Buell Tomasson} and Chris Smith",
year = "2002",
month = "6",
day = "1",
doi = "10.1086/340051",
language = "English (US)",
volume = "571",
pages = "721--732",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "2 I",

}

TY - JOUR

T1 - Chandra observations of the QSO pair Q2345+007

T2 - Binary or massive dark lens?

AU - Green, Paul J.

AU - Kochanek, Chris

AU - Siemiginowska, Aneta

AU - Kim, Dong Woo

AU - Markevitch, Maxim

AU - Silverman, John

AU - Dosaj, Anil

AU - Jannuzi, Buell Tomasson

AU - Smith, Chris

PY - 2002/6/1

Y1 - 2002/6/1

N2 - The components of the wide (7″.3) separation quasar pair Q2345+007A, B (z = 2.15) have the most strikingly similar optical spectra seen to date (Steidel & Sargent) yet no detected lensing mass, making this system the best candidate known for a massive (∼1014 M⊙) dark matter lens system. Here we present results from a 65 ks Chandra observation designed to investigate whether it is a binary quasar or a gravitational lens. We find no X-ray evidence for a lensing cluster to a (0.5-2 keV) flux limit of 2 × 10-15 ergs cm-2 s -1, which is consistent with lensing only for a reduced baryon fraction. Using the Chandra X-ray observations of the quasars themselves, together with new and published optical measurements, we use the observed emission properties of the quasars for further tests between the lens and binary hypotheses. Assuming similar line-of-sight absorption to the images, we find that their X-ray continuum slopes are inconsistent (ΓA = 2.30-0.30+0.36 and ΓB = 0.83 -0.44+0.49) as are their X-ray-to-optical flux ratios. The probability that B suffers intrinsic absorption sufficient to account for these spectral differences is negligible. We present new optical evidence that the flux ratio of the pair is variable, so the time delay in a lens scenario could cause some of the discrepancies. However, adequately large variations in overall spectral energy distribution are rare in individual QSOs. All new evidence here weighs strongly toward the binary interpretation. Q2345+007 thus may represent the highest redshift example known of an interaction-triggered but as-yet unmerged luminous active galactic nucleus.

AB - The components of the wide (7″.3) separation quasar pair Q2345+007A, B (z = 2.15) have the most strikingly similar optical spectra seen to date (Steidel & Sargent) yet no detected lensing mass, making this system the best candidate known for a massive (∼1014 M⊙) dark matter lens system. Here we present results from a 65 ks Chandra observation designed to investigate whether it is a binary quasar or a gravitational lens. We find no X-ray evidence for a lensing cluster to a (0.5-2 keV) flux limit of 2 × 10-15 ergs cm-2 s -1, which is consistent with lensing only for a reduced baryon fraction. Using the Chandra X-ray observations of the quasars themselves, together with new and published optical measurements, we use the observed emission properties of the quasars for further tests between the lens and binary hypotheses. Assuming similar line-of-sight absorption to the images, we find that their X-ray continuum slopes are inconsistent (ΓA = 2.30-0.30+0.36 and ΓB = 0.83 -0.44+0.49) as are their X-ray-to-optical flux ratios. The probability that B suffers intrinsic absorption sufficient to account for these spectral differences is negligible. We present new optical evidence that the flux ratio of the pair is variable, so the time delay in a lens scenario could cause some of the discrepancies. However, adequately large variations in overall spectral energy distribution are rare in individual QSOs. All new evidence here weighs strongly toward the binary interpretation. Q2345+007 thus may represent the highest redshift example known of an interaction-triggered but as-yet unmerged luminous active galactic nucleus.

KW - Gravitational lensing

KW - Quasars: absorption lines

KW - X-rays: general

UR - http://www.scopus.com/inward/record.url?scp=0041342306&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0041342306&partnerID=8YFLogxK

U2 - 10.1086/340051

DO - 10.1086/340051

M3 - Article

VL - 571

SP - 721

EP - 732

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 2 I

ER -