Spitzer Space Telescope - Directors Discretionary Time Proposal #234


The Supermassive Black Hole in Arp102B

Principal Investigator: Harlan Devore
           Institution: Cape Fear High School

Co-Investigators: 
Lauren Chapple, Traverse City East Junior High School                 
Howard Chun, Cranston High School                                     
Doris Daou, Spitzer Science Center                                    

Science Category: nearby galaxies (z<0.05, v_sys<15,000 km/s) 
 Observing Modes: IrsStare 
  Hours Approved: 0.5 

Abstract:
Arp102B is a radio-loud, Seyfert 1 galaxy located in the constellation
Hercules with a B-band magnitude of 15.2 mag.  It has a redshift z =
0.024, giving it a recessional velocity of 7250  km/s and a distance
of about 99.1Mpc.  At its core is a low luminosity AGN with a black
hole estimated to be ~108 solar masses.  Although there have been many
radio, X-ray, UV, optical, and ground-based IR studies of the Arp102B
nucleus, they have not converged to produce a single, unified model
for the nucleus.  For example, Chen and Halpern (1989) used a
geometrically thin, optically thick accretion disk model to fit
double-peaked Balmer lines in the spectrum of Arp102B.  Sulentic
(1998) suggested that a bicone model would better fit the Fe K alpha
lines in the x-ray spectrum.  Korista summarizes the current state of
our understanding as follows:  "Despite significant progress, some
fundamental issues relating to the geometry of the broad line emitting
gas remain unsolved.  We do not know whether in general the broad line
region is composed of discrete clouds, winds, disks, or bloated
stellar atmospheres or a combination of these." (Strateva et al.,
2003).  We believe that quality spectral data covering the IR spectrum
may be the key to resolving these differences and could lead to a
unified model for this type of AGN.  Therefore, we propose to use
Spitzer's IRS instrument to obtain LH, SH, SL1 and SL2 spectral data
of Arp102's supermassive blackhole.  With this data, we can measure
the mass of the black hole, analyze the geometry, composition, and
physical properties of the dust structure surrounding the black hole
and reach conclusions about the energy production mechanism(s) in the
nucleus.