Restframe UV-to-optical spectroscopy of APM 08279+5255. BAL classification and black hole mass estimates
Abstract
We present the analysis of the restframe optical-to-UV spectrum of APM 08279+5255, a well-known lensed broad absorption line (BAL) quasar at z = 3.911. The spectroscopic data were taken with the optical DOLoRes and near-IR NICS instruments at TNG, and include the previously unexplored range between C III] λ1910 and [O III] λλ4959,5007. We have investigated the possible presence of multiple BALs by computing "balnicity" and absorption indexes (i.e., BI, BI0, and AI) for the transitions Si IV λ1400, C IV λ1549, Al III λ1860, and Mg II λ2800. No clear evidence for the presence of absorption features is found in addition to the already known, prominent BAL associated to C IV, which supports a high-ionization BAL classification for APM 08279+5255. We also studied the properties of the [O III], Hβ, and Mg II emission lines. We find that [O III] is intrinsically weak (F[OIII]/FHβ ≲ 0.04), as it is typically found in luminous quasars with a strongly blueshifted C IV emission line ( 2500 km s-1 for APM 08279+5255). We computed the single-epoch black hole mass based on Mg II and Hβ broad emission lines, finding MBH = (2 ÷ 3) × 1010μ-1 M⊙, with the magnification factor μ that can vary between 4 and 100 according to CO and restframe UV-to-mid-IR imaging respectively. Using a Mg II equivalent width (EW)-to-Eddington ratio relation, the EWMgII 27 Å measured for APM 08279+5255 translates into an Eddington ratio of 0.4, which is more consistent with μ = 4. This magnification factor also provides a value of MBH that is consistent with recent reverberation-mapping measurements derived from C IV and Si IV.
The reduced spectrum is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/617/A118- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- September 2018
- DOI:
- 10.1051/0004-6361/201832794
- arXiv:
- arXiv:1804.10038
- Bibcode:
- 2018A&A...617A.118S
- Keywords:
-
- galaxies: active;
- quasars: general;
- quasars: absorption lines;
- quasars: emission lines;
- quasars: supermassive black holes;
- quasars: individual: APM 08279+5255;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 10 pages, 4 figures, 4 tables, accepted for publication in A&