The Discovery of an Active Galactic Nucleus in the Late-Type Galaxy NGC 3621:
                    <i>Spitzer</i>
                    Spectroscopic Observations

Satyapal, S.; Vega, Devin; Heckman, T. M.; O’Halloran, B.; Dudik, R. P.

doi:10.1086/519995

Cited by 116 publications

(145 citation statements)

References 37 publications

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“…Other MIR searches are based on the detection of the high-ionization emission line [NeV] 14 µm or the 24 µm line using Spitzer spectral observations. This yielded the detection of 9 AGN in bulgeless or late-type (with a minimal bulge) galaxies, for which a lower limit on the BH mass ranging from ∼ 3 × 10 3 − 1.5 × 10 5 M was estimated assuming sub-Eddington accretion (Satyapal et al 2007(Satyapal et al , 2008(Satyapal et al , 2009). Follow-up observations with the XMMNewton X-ray satellite revealed the presence of hard, unresolved X-ray emission in one of these bulgeless dwarf galaxies (J1329+3234), with an X-ray luminosity (L X = 2.4 × 10 40 erg s −1 ) two orders of magnitude larger than that expected from star formation and consistent with an accreting BH (Secrest et al 2015).…”

Section: Dwarf Galaxiesmentioning

confidence: 98%

Observational evidence for intermediate-mass black holes

Mezcua

2017

Int. J. Mod. Phys. D

268

219

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Intermediate-mass black holes (IMBHs), with masses in the range 100 − 10 6 M , are the link between stellar-mass BHs and supermassive BHs (SMBHs). They are thought to be the seeds from which SMBHs grow, which would explain the existence of quasars with BH masses of up to 10 10 M when the Universe was only 0.8 Gyr old. The detection and study of IMBHs has thus strong implications for understanding how SMBHs form and grow, which is ultimately linked to galaxy formation and growth, as well as for studies of the universality of BH accretion or the epoch of reionisation. Proving the existence of seed BHs in the early Universe is not yet feasible with the current instrumentation; however, those seeds that did not grow into SMBHs can be found as IMBHs in the nearby Universe. In this review I summarize the different scenarios proposed for the formation of IMBHs and gather all the observational evidence for the few hundreds of nearby IMBH candidates found in dwarf galaxies, globular clusters, and ultraluminous X-ray sources, as well as the possible discovery of a few seed BHs at high redshift. I discuss some of their properties, such as X-ray weakness and location in the BH mass scaling relations, and the possibility to discover IMBHs through high velocity clouds, tidal disruption events, gravitational waves, or accretion disks in active galactic nuclei. I finalize with the prospects for the detection of IMBHs with up-coming observatories.

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Section: Dwarf Galaxiesmentioning

confidence: 98%

Observational evidence for intermediate-mass black holes

Mezcua

2017

Int. J. Mod. Phys. D

268

219

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“…Nuclear star clusters do not appear to directly impact a galaxy's ability to host an AGN (Seth et al 2008). Several serendipitous cases of AGNs in late-type galaxies have recently been found from analysis of Spitzer mid-IR spectra (Satyapal et al 2007(Satyapal et al , 2008, as well as a number of AGN candidates from inspection of Chandra images (Desroches & Ho 2008). Among earlier Hubble types, Gallo et al (2008) report the detection of X-ray nuclei in two low-luminosity early-type galaxies.…”

Section: Implications For Black Hole Demographicsmentioning

confidence: 99%

Nuclear Activity in Nearby Galaxies

2008

Annu. Rev. Astron. Astrophys.

1,122

104

1,195

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A significant fraction of nearby galaxies show evidence of weak nuclear activity unrelated to normal stellar processes. Recent high-resolution, multiwavelength observations indicate that the bulk of this activity derives from black hole accretion with a wide range of accretion rates. The low accretion rates that typify most low-luminosity active galactic nuclei induce significant modifications to their central engine. The broad-line region and obscuring torus disappear in some of the faintest sources, and the optically thick accretion disk transforms into a three-component structure consisting of an inner radiatively inefficient accretion flow, a truncated outer thin disk, and a jet or outflow. The local census of nuclear activity supports the notion that most, perhaps all, bulges host a central supermassive black hole, although the existence of active nuclei in at least some late-type galaxies suggests that a classical bulge is not a prerequisite to seed a nuclear black hole.

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“…Determining the true space densities of low-mass BHs from the SDSS surveys is very difficult because of the joint bias toward luminous galaxies (for spectroscopic targeting) and luminous AGNs (for spectroscopic identification; Greene & Ho 2007b). Searches based on mid-infrared (e.g., Spitzer spectroscopy; Satyapal et al 2007Satyapal et al , 2008Satyapal et al , 2009Goulding et al 2010) or X-ray observations (Ghosh et al 2008;Desroches & Ho 2009;Gallo et al 2008Gallo et al , 2010Kamizasa et al 2012;Schramm et al 2013) have so far covered only small volumes, often with heterogeneous selection.…”

Section: Introductionmentioning

confidence: 99%

Dwarf Galaxies With Optical Signatures of Active Massive Black Holes

Reines

Greene

Geha

2013

ApJ

518

829

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We present a sample of 151 dwarf galaxies (10 8.5 M 10 9.5 M ) that exhibit optical spectroscopic signatures of accreting massive black holes (BHs), increasing the number of known active galaxies in this stellar-mass range by more than an order of magnitude. Utilizing data from the Sloan Digital Sky Survey Data Release 8 and stellar masses from the NASA-Sloan Atlas, we have systematically searched for active BHs in ∼25,000 emission-line galaxies with stellar masses comparable to the Magellanic Clouds and redshifts z < 0.055. Using the narrow-line [O iii]/Hβ versus [N ii]/Hα diagnostic diagram, we find photoionization signatures of BH accretion in 136 galaxies, a small fraction of which also exhibit broad Hα emission. For these broad-line active galactic nucleus (AGN) candidates, we estimate BH masses using standard virial techniques and find a range of 10 5 M BH 10 6 M and a median of M BH ∼ 2 × 10 5 M . We also detect broad Hα in 15 galaxies that have narrow-line ratios consistent with star-forming galaxies. Follow-up observations are required to determine if these are true type 1 AGN or if the broad Hα is from stellar processes. The median absolute magnitude of the host galaxies in our active sample is M g = −18.1 mag, which is ∼1-2 mag fainter than previous samples of AGN hosts with low-mass BHs. This work constrains the smallest galaxies that can form a massive BH, with implications for BH feedback in low-mass galaxies and the origin of the first supermassive BH seeds.

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The Discovery of an Active Galactic Nucleus in the Late-Type Galaxy NGC 3621: Spitzer Spectroscopic Observations

Cited by 116 publications

References 37 publications

Observational evidence for intermediate-mass black holes

Observational evidence for intermediate-mass black holes

Nuclear Activity in Nearby Galaxies

Dwarf Galaxies With Optical Signatures of Active Massive Black Holes

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