Volume 617, September 2018
|Number of page(s)||10|
|Published online||26 September 2018|
Restframe UV-to-optical spectroscopy of APM 08279+5255
BAL classification and black hole mass estimates★
INAF – Osservatorio Astronomico di Roma,
Via Frascati 33,
Monte Porzio Catone (RM),
2 Space Science Data Center, Agenzia Spaziale Italiana, Via del Politecnico snc, 00133 Roma, Italy
3 Dip. di Fisica, Università degli Studi di Roma “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Roma, Italy
4 INAF – Osservatorio Astronomico di Brera, Via Brera 28, 20121 Milano, Italy
5 INAF – Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy
6 Scuola Normale Superiore, P.zza dei Cavalieri 7, 56126 Pisa, Italy
7 SRON – Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
8 Excellence Cluster Universe, Technische Universität München, Boltzmannstr. 2, 85748 Garching b. München, Germany
9 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching b. München, Germany
10 Dip. di Fisica e Astronomia, Alma Mater Studiorum, Università degli Studi di Bologna, Via P. Gobetti 93/2, 40129 Bologna, Italy
11 INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via P. Gobetti 93/3. 40129 Bologna, Italy
Accepted: 24 April 2018
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.
Key words: galaxies: active / quasars: general / quasars: absorption lines / quasars: emission lines / quasars: supermassive black holes / quasars: individual: APM 08279+5255
The reduced spectrum is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (18.104.22.168) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/617/A118
© ESO 2018
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