Measurement of an active galactic nucleus central mass on centiparsec scales: Results of long-term optical monitoring of Arp 102B

Jeffrey A. Newman, Michael Eracleous, Alexei V. Filippenko, Jules P. Halpern

Research output: Contribution to journalArticle

38 Citations (Scopus)

Abstract

The optical spectrum of the broad-line radio galaxy Arp 102B has been monitored for more than 13 yr to investigate the nature of the source of its broad, double-peaked hydrogen Balmer emission lines. The shape of the lines varied subtly; there was an interval during which the variation in the ratio of the fluxes of the two peaks appeared to be sinusoidal, with a period of 2.16 yr and an amplitude of about 16% of the average value. The variable part of the broad Hα line is well fitted by a model in which a region of excess emission (a quiescent "hot spot") within an accretion disk (fitted to the nonvarying portion of the double-peaked line) completes at least two circular orbits and eventually fades. Fits to spectra from epochs when the hot spot is not present allow determination of the disk inclination, while fits for epochs when it is present provide a measurement of the radius of the hot spot's orbit. From these data and the period of variation, we find that the mass within the hot spot's orbit is 2.2-0.7+0.7 × 108 M⊙, within the range of previous estimates of masses of active galactic nuclei. Because this mass is determined at a relatively small distance from the central body, it is extremely difficult to explain without assuming that a supermassive black hole lies within Arp 102B. Our collection of spectra allows us to apply several tests to models of the source of the double peaks. The ratio of Hα to Hβ flux at a given velocity displays no turning points or points of inflection at the velocity associated with the blue peak in flux; thus, this peak should not correspond to a turning point in physical conditions. This behavior is consistent with simple accretion disk and, possibly, spiral shock models but not with models that attribute the double peaks to separate broad-line regions around a binary black hole or to broad, subrelativistic jets. The lack of systematic change in the velocity of the blue peak over time provides a further constraint on binary broad-line region models; this yields a lower limit on the mass of such a binary black hole system of at least 1010 M⊙. The variability properties of the double-peaked emission lines in Arp 102B therefore continue to favor an accretion disk origin over other models.

Original languageEnglish (US)
Pages (from-to)570-580
Number of pages11
JournalAstrophysical Journal
Volume485
Issue number2 PART I
DOIs
StatePublished - Jan 1 1997

Fingerprint

active galactic nuclei
hot spot
monitoring
accretion disks
accretion
time measurement
orbits
circular orbits
radio galaxies
inclination
optical spectrum
shock
hydrogen
radio
intervals
radii
estimates

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Newman, Jeffrey A. ; Eracleous, Michael ; Filippenko, Alexei V. ; Halpern, Jules P. / Measurement of an active galactic nucleus central mass on centiparsec scales : Results of long-term optical monitoring of Arp 102B. In: Astrophysical Journal. 1997 ; Vol. 485, No. 2 PART I. pp. 570-580.
@article{a93850521adc41e7bbd5e86a8329ce85,
title = "Measurement of an active galactic nucleus central mass on centiparsec scales: Results of long-term optical monitoring of Arp 102B",
abstract = "The optical spectrum of the broad-line radio galaxy Arp 102B has been monitored for more than 13 yr to investigate the nature of the source of its broad, double-peaked hydrogen Balmer emission lines. The shape of the lines varied subtly; there was an interval during which the variation in the ratio of the fluxes of the two peaks appeared to be sinusoidal, with a period of 2.16 yr and an amplitude of about 16{\%} of the average value. The variable part of the broad Hα line is well fitted by a model in which a region of excess emission (a quiescent {"}hot spot{"}) within an accretion disk (fitted to the nonvarying portion of the double-peaked line) completes at least two circular orbits and eventually fades. Fits to spectra from epochs when the hot spot is not present allow determination of the disk inclination, while fits for epochs when it is present provide a measurement of the radius of the hot spot's orbit. From these data and the period of variation, we find that the mass within the hot spot's orbit is 2.2-0.7+0.7 × 108 M⊙, within the range of previous estimates of masses of active galactic nuclei. Because this mass is determined at a relatively small distance from the central body, it is extremely difficult to explain without assuming that a supermassive black hole lies within Arp 102B. Our collection of spectra allows us to apply several tests to models of the source of the double peaks. The ratio of Hα to Hβ flux at a given velocity displays no turning points or points of inflection at the velocity associated with the blue peak in flux; thus, this peak should not correspond to a turning point in physical conditions. This behavior is consistent with simple accretion disk and, possibly, spiral shock models but not with models that attribute the double peaks to separate broad-line regions around a binary black hole or to broad, subrelativistic jets. The lack of systematic change in the velocity of the blue peak over time provides a further constraint on binary broad-line region models; this yields a lower limit on the mass of such a binary black hole system of at least 1010 M⊙. The variability properties of the double-peaked emission lines in Arp 102B therefore continue to favor an accretion disk origin over other models.",
author = "Newman, {Jeffrey A.} and Michael Eracleous and Filippenko, {Alexei V.} and Halpern, {Jules P.}",
year = "1997",
month = "1",
day = "1",
doi = "10.1086/304460",
language = "English (US)",
volume = "485",
pages = "570--580",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "2 PART I",

}

Measurement of an active galactic nucleus central mass on centiparsec scales : Results of long-term optical monitoring of Arp 102B. / Newman, Jeffrey A.; Eracleous, Michael; Filippenko, Alexei V.; Halpern, Jules P.

In: Astrophysical Journal, Vol. 485, No. 2 PART I, 01.01.1997, p. 570-580.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Measurement of an active galactic nucleus central mass on centiparsec scales

T2 - Results of long-term optical monitoring of Arp 102B

AU - Newman, Jeffrey A.

AU - Eracleous, Michael

AU - Filippenko, Alexei V.

AU - Halpern, Jules P.

PY - 1997/1/1

Y1 - 1997/1/1

N2 - The optical spectrum of the broad-line radio galaxy Arp 102B has been monitored for more than 13 yr to investigate the nature of the source of its broad, double-peaked hydrogen Balmer emission lines. The shape of the lines varied subtly; there was an interval during which the variation in the ratio of the fluxes of the two peaks appeared to be sinusoidal, with a period of 2.16 yr and an amplitude of about 16% of the average value. The variable part of the broad Hα line is well fitted by a model in which a region of excess emission (a quiescent "hot spot") within an accretion disk (fitted to the nonvarying portion of the double-peaked line) completes at least two circular orbits and eventually fades. Fits to spectra from epochs when the hot spot is not present allow determination of the disk inclination, while fits for epochs when it is present provide a measurement of the radius of the hot spot's orbit. From these data and the period of variation, we find that the mass within the hot spot's orbit is 2.2-0.7+0.7 × 108 M⊙, within the range of previous estimates of masses of active galactic nuclei. Because this mass is determined at a relatively small distance from the central body, it is extremely difficult to explain without assuming that a supermassive black hole lies within Arp 102B. Our collection of spectra allows us to apply several tests to models of the source of the double peaks. The ratio of Hα to Hβ flux at a given velocity displays no turning points or points of inflection at the velocity associated with the blue peak in flux; thus, this peak should not correspond to a turning point in physical conditions. This behavior is consistent with simple accretion disk and, possibly, spiral shock models but not with models that attribute the double peaks to separate broad-line regions around a binary black hole or to broad, subrelativistic jets. The lack of systematic change in the velocity of the blue peak over time provides a further constraint on binary broad-line region models; this yields a lower limit on the mass of such a binary black hole system of at least 1010 M⊙. The variability properties of the double-peaked emission lines in Arp 102B therefore continue to favor an accretion disk origin over other models.

AB - The optical spectrum of the broad-line radio galaxy Arp 102B has been monitored for more than 13 yr to investigate the nature of the source of its broad, double-peaked hydrogen Balmer emission lines. The shape of the lines varied subtly; there was an interval during which the variation in the ratio of the fluxes of the two peaks appeared to be sinusoidal, with a period of 2.16 yr and an amplitude of about 16% of the average value. The variable part of the broad Hα line is well fitted by a model in which a region of excess emission (a quiescent "hot spot") within an accretion disk (fitted to the nonvarying portion of the double-peaked line) completes at least two circular orbits and eventually fades. Fits to spectra from epochs when the hot spot is not present allow determination of the disk inclination, while fits for epochs when it is present provide a measurement of the radius of the hot spot's orbit. From these data and the period of variation, we find that the mass within the hot spot's orbit is 2.2-0.7+0.7 × 108 M⊙, within the range of previous estimates of masses of active galactic nuclei. Because this mass is determined at a relatively small distance from the central body, it is extremely difficult to explain without assuming that a supermassive black hole lies within Arp 102B. Our collection of spectra allows us to apply several tests to models of the source of the double peaks. The ratio of Hα to Hβ flux at a given velocity displays no turning points or points of inflection at the velocity associated with the blue peak in flux; thus, this peak should not correspond to a turning point in physical conditions. This behavior is consistent with simple accretion disk and, possibly, spiral shock models but not with models that attribute the double peaks to separate broad-line regions around a binary black hole or to broad, subrelativistic jets. The lack of systematic change in the velocity of the blue peak over time provides a further constraint on binary broad-line region models; this yields a lower limit on the mass of such a binary black hole system of at least 1010 M⊙. The variability properties of the double-peaked emission lines in Arp 102B therefore continue to favor an accretion disk origin over other models.

UR - http://www.scopus.com/inward/record.url?scp=21744456137&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=21744456137&partnerID=8YFLogxK

U2 - 10.1086/304460

DO - 10.1086/304460

M3 - Article

AN - SCOPUS:21744456137

VL - 485

SP - 570

EP - 580

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 2 PART I

ER -