J/A+A/620/A137 CCD B,V,R,I,Ha photometry of 3C120 (Ramolla+, 2018)
Simultaneous Hα and dust reverberation mapping of 3C120:
Testing the bowl-shaped torus geometry.
Ramolla M., Haas M., Westhues C., Pozo Nunez F., Sobrino Figaredo C.,
Blex J., Zetzl M., Kollatschny W., Chini R., Murphy M.
<Astron. Astrophys. 620, A137 (2018)>
=2018A&A...620A.137R 2018A&A...620A.137R (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei; Galaxies, photometry; Photometry, UBVRI;
Photometry, H-alpha
Keywords: galaxies: Seyfert - quasars: emission lines - infrared: galaxies -
galaxies: nuclei - galaxies: structure -
quasars: supermassive black holes
Abstract:
At the Universitaetssternwarte Bochum near Cerro Armazones we have
monitored the Seyfert-1 galaxy 3C 120 between September 2014 and March
2015 in BVRI and a narrow band filter covering the redshifted Hα
line; in addition we obtained a single con-temporary spectrum with
FAST at Mt. Hopkins. Compared to earlier epochs 3C 120 is about a
factor of three brighter, allowing us to study the shape of the broad
line region (BLR) and the dust torus in a high luminosity phase. The
analysis of the light curves yields that the dust echo is rather sharp
and symmetric in contrast to the more complex broad Hα BLR echo.
We investigate how far this supports an optically thick bowl-shaped
BLR and dust torus geometry as proposed by Kawaguchi & Mori
(2010ApJ...724L.183K 2010ApJ...724L.183K) and Goad et al. (2012MNRAS.426.3086G 2012MNRAS.426.3086G). The
comparison with several parameterizations of these models supports the
following geometry: the BLR clouds lie inside the bowl closely above
the bowl rim, up to a half covering angle 0°<theta<40°
(measured against the equatorial plane). Then the BLR is spread over
many isodelay surfaces, yielding a smeared and structured echo as
observed. Furthermore, if the BLR clouds shield the bottom of the bowl
rim against radiation from the nucleus, the hot dust emission comes
essentially from the top edge of the bowl (40°<theta< 45°).
Then, for small inclinations as for 3C120, the top dust edge forms a
ring which largely coincides with a narrow range of isodelay surfaces,
yielding the observed sharp dust echo. The scale height of the BLR
increases with radial distance from the black hole. This leads to
luminosity dependent foreshortening effects of the lag. We discuss
implications and possible corrections of the foreshortening for the
black hole mass determination and consequences for the lag (size) -
luminosity relationships and the difference to interferometric torus
sizes.
Description:
The photometric data was reduced with standard IRAF bias, dark, and
flatfield correction. Astrometric matching was performed with Scamp
(Bertin, 2006, ASP Conf. Ser., 351, 112). Before stacking multiple
exposures, they were resampled onto a common coordinate grid using
Swarp (Bertin et al. 2002). The photometry is performed on combined
frames with a fixed 7.5-arcs aperture, found to be the optimum in our
previous studies (Haas et al. 2011A&A...535A..73H 2011A&A...535A..73H; Pozo Nunez et al.
2012A&A...545A..84P 2012A&A...545A..84P, 2013A&A...552A...1P 2013A&A...552A...1P, 2015A&A...576A..73P 2015A&A...576A..73P; Ramolla
et al. 2015A&A...581A..93R 2015A&A...581A..93R). Our aim is to combine relative photometry
in the field with absolute photometry anchored to Landolt fields.
First, we select 20 close non-variable stars (calibrators) in the AGN
field with brightness ranging from 0.5 to 10 times of the nuclear
3C 120 flux. Then, photometry of 3C 120 and these stars is performed
using the 7.5-arcs aperture with SExtractor (Bertin & Arnouts
1996A&AS..117..393B 1996A&AS..117..393B). The calibrator lightcurves are normalized to
their average over all days in the observation epoch. The scatter of
the normal- ized ensemble of calibrators within a particular night is
used as relative photometric error. Dividing the flux of 3C 120 by the
nightly average of the normalized ensemble results in the relative
lightcurve of the target.
Objects:
-----------------------------------------------
RA (2000) DE Designation(s)
-----------------------------------------------
04 33 11.10 +05 21 15.6 3C 120 = Mrk 1506
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
3c120ha.dat 27 64 3C 120 680nm narrow band (Hα) observations
3c120bj.dat 27 108 3C 120 Johnson B observations
3c120vj.dat 27 97 3C 120 Johnson V observations
3c120rj.dat 27 93 3C 120 Johnson R observations
3c120ij.dat 27 39 3C 120 Johnson I observations
spec-cal.fits 2880 8 3C 120 calibrated spectrum
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See also:
J/PAZh/35/403 : Optical Variabilities in 3C 120 (Doroshenko+, 2009)
J/ApJ/808/162 : VLBA 15 and 43GHz obs. of 3C 120 (Casadio+, 2015)
Byte-by-byte Description of file: 3c120*.dat
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Bytes Format Units Label Explanations
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1- 9 F9.3 d MJD Modified Julian Date
13- 18 F6.3 mJy Flux Flux
23- 27 F5.3 mJy e_Flux Flux error
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Acknowledgements:
We are grateful to Emilio E. Falco and Marco Berton for supporting us
with recent spectroscopy. This research has made use of the NASA/IPAC
Extragalactic Database (NED) which is operated by the Jet Propul- sion
Laboratory, California Institute of Technology, under contract with
the National Aeronautics and Space Administration. This publication is
supported as a project of the Nordrhein-Westfaelische Akademie der
Wissenschaften und der Kuenste in the framework of the academy program
by the Federal Republic of Germany and the state Nordrhein-Westfalen.
This work is supported by the DFG programs Ha 3555/12-1, Ko 857/32-2
and Ko 857/33-1. The observations on Cerro Armazones benefited from
the care of the guardians Hector Labra, Gerardo Pino, Roberto Munoz,
and Francisco Arraya. We thank the referee for critical and
constructive comments.
Michael Ramolla, ramolla(at)astro.rub.de
(End) Michael Ramolla [AIRUB, Germany], Patricia Vannier [CDS] 10-Aug-2018