Abstract
We report on the discovery of a peculiar broad absorption line (BAL) quasar identified in our Gaia-assisted survey of red quasars. The systemic redshift of this quasar was difficult to establish because of the absence of conspicuous emission lines. Based on deep and broad BAL troughs of at least Six202f;IV, Cx202f;IV, and Alx202f;III, a redshift of zx2004;=& x2004;2.41 was established under the assumption that the systemic redshift can be inferred from the red edge of the BAL troughs. However, we observe a weak and spatially extended emission line at 4450 angstrom that is most likely due to Lyman-alpha emission, which implies a systemic redshift of zx2004;=x2004;2.66 if correctly identified. There is also evidence for the onset of Lyman-alpha forest absorption bluewards of 4450 angstrom and evidence for H alpha emission in the K band consistent with a systemic redshift of zx2004;=& x2004;2.66. If this redshift is correct, the quasar is an extreme example of a detached low-ionisation BAL quasar. The BALs must originate from material moving with very large velocities ranging from 22 000 km s(-1) to 40 000 km s(-1). To our knowledge, this is the first case of a systemic-redshift measurement based on extended Lyman-alpha emission for a BAL quasar. This method could also be useful in cases of sufficiently distant BL Lac quasars without systemic-redshift information.
| Original language | English |
|---|---|
| Article number | A111 |
| Journal | Astronomy & Astrophysics |
| Volume | 634 |
| Number of pages | 6 |
| ISSN | 0004-6361 |
| DOIs | |
| Publication status | Published - 19 Feb 2020 |
Funding
We thank the anonymous referee for a very helpful and constructive report. We also thank Raghunathan Srianand, Yeimin Yi, Marianne Vestergaard, Sandra Raimundo, and Kimihiko Nakajima for helpful discussions. Based on observations made with the Gran Telescopio Canarias (GTC), the William Herschel Telescope (WHT), and with the Nordic Optical Telescope (NOT), installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, on the island of La Palma. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognise and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This work is partly based on data obtained through the UKIRT Infrared Deep Sky Survey. The Cosmic Dawn Center is funded by the DNRF. KEH and PJ acknowledge support by a Project Grant (162948-051) from The Icelandic Research Fund. L. C. is supported by the Independent Research Fund Denmark (DFF-4090-00079). J. K. K. and P. N. acknowledge support from the French Agence Nationale de la Recherche under grant no ANR-17-CE31-0011-01 (project HIH2 - PI: Noterdaeme). B. M. J. is supported in part by Independent Research Fund Denmark grant DFF - 7014-00017. J. P. U. F. thanks the Carlsberg Foundation for support.
Keywords
- quasars
- general
- absorption lines
- individual
- GQ 1309+2604
- BROAD ABSORPTION-LINE
- LYMAN-ALPHA EMISSION
- POLARIZATION PROPERTIES
- SKY
- VARIABILITY
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