The multitude of unresolved continuum sources at 1.6 microns in Hubble Space Telescope images of Seyfert galaxies

A. C. Quillen, Colleen McDonald, A. Alonso-Herrero, Ariane Lee, Shanna Shaked, Marcia J Rieke, George H. Rieke

Research output: Contribution to journalArticle

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Abstract

We examine 112 Seyfert galaxies observed by the Hubble Space Telescope at 1.6 μm. We find that ∼ 50% of the Seyfert 2.0 galaxies which are part of the Revised Shapely-Ames (RSA) Catalog or the CfA redshift sample contain unresolved continuum sources at 1.6 μm. All but a couple of the Seyfert 1.0-1.9 galaxies display unresolved continuum sources. The unresolved sources have fluxes of order 1 mJy, near infrared luminosities of order 1041 ergs s-1, and absolute magnitudes MH ∼ -16. Comparison non-Seyfert galaxies from the RSA Catalog display significantly fewer (∼20%), somewhat lower luminosity nuclear sources, which could be due to compact star clusters. We find that the luminosities of the unresolved Seyfert 1.0-1.9 sources at 1.6 μm are correlated with [O III] λ15007 and hard X-ray luminosities, implying that these sources are nonstellar. Assuming a spectral energy distribution similar to that of a Seyfert 2 galaxy, we estimate that a few percent of local spiral galaxies contain black holes emitting as Seyferts at a moderate fraction, ∼10-1-10-4, of their Eddington luminosities. We find no strong correlation between 1.6 μm fluxes and hard X-ray or [O III] λ5007 fluxes for the pure Seyfert 2.0 galaxies. These galaxies also tend to have lower 1.6 μm luminosities compared to the Seyfert 1.0-1.9 galaxies of similar [O III] luminosity. Either large extinctions (AV ∼ 20-40) are present toward their continuumemitting regions or some fraction of the unresolved sources at 1.6 μ are compact star clusters. With increasing Seyfert type the fraction of unresolved sources detected at 1.6 μm and the ratio of 1.6 μm to [O III] fluxes tend to decrease. These trends are consistent with the unification model for Seyfert 1 and 2 galaxies.

Original languageEnglish (US)
Pages (from-to)129-139
Number of pages11
JournalAstrophysical Journal
Volume547
Issue number1 PART 1
DOIs
StatePublished - Jan 20 2001

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Seyfert galaxies
Hubble Space Telescope
continuums
luminosity
galaxies
star clusters
catalogs
erg
spiral galaxies
spectral energy distribution
near infrared
extinction
x rays
trends
estimates
energy

Keywords

  • Galaxies: nuclei
  • Galaxies: Seyfert
  • Galaxies: spiral

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

The multitude of unresolved continuum sources at 1.6 microns in Hubble Space Telescope images of Seyfert galaxies. / Quillen, A. C.; McDonald, Colleen; Alonso-Herrero, A.; Lee, Ariane; Shaked, Shanna; Rieke, Marcia J; Rieke, George H.

In: Astrophysical Journal, Vol. 547, No. 1 PART 1, 20.01.2001, p. 129-139.

Research output: Contribution to journalArticle

Quillen, A. C. ; McDonald, Colleen ; Alonso-Herrero, A. ; Lee, Ariane ; Shaked, Shanna ; Rieke, Marcia J ; Rieke, George H. / The multitude of unresolved continuum sources at 1.6 microns in Hubble Space Telescope images of Seyfert galaxies. In: Astrophysical Journal. 2001 ; Vol. 547, No. 1 PART 1. pp. 129-139.
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abstract = "We examine 112 Seyfert galaxies observed by the Hubble Space Telescope at 1.6 μm. We find that ∼ 50{\%} of the Seyfert 2.0 galaxies which are part of the Revised Shapely-Ames (RSA) Catalog or the CfA redshift sample contain unresolved continuum sources at 1.6 μm. All but a couple of the Seyfert 1.0-1.9 galaxies display unresolved continuum sources. The unresolved sources have fluxes of order 1 mJy, near infrared luminosities of order 1041 ergs s-1, and absolute magnitudes MH ∼ -16. Comparison non-Seyfert galaxies from the RSA Catalog display significantly fewer (∼20{\%}), somewhat lower luminosity nuclear sources, which could be due to compact star clusters. We find that the luminosities of the unresolved Seyfert 1.0-1.9 sources at 1.6 μm are correlated with [O III] λ15007 and hard X-ray luminosities, implying that these sources are nonstellar. Assuming a spectral energy distribution similar to that of a Seyfert 2 galaxy, we estimate that a few percent of local spiral galaxies contain black holes emitting as Seyferts at a moderate fraction, ∼10-1-10-4, of their Eddington luminosities. We find no strong correlation between 1.6 μm fluxes and hard X-ray or [O III] λ5007 fluxes for the pure Seyfert 2.0 galaxies. These galaxies also tend to have lower 1.6 μm luminosities compared to the Seyfert 1.0-1.9 galaxies of similar [O III] luminosity. Either large extinctions (AV ∼ 20-40) are present toward their continuumemitting regions or some fraction of the unresolved sources at 1.6 μ are compact star clusters. With increasing Seyfert type the fraction of unresolved sources detected at 1.6 μm and the ratio of 1.6 μm to [O III] fluxes tend to decrease. These trends are consistent with the unification model for Seyfert 1 and 2 galaxies.",
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AU - Shaked, Shanna

AU - Rieke, Marcia J

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N2 - We examine 112 Seyfert galaxies observed by the Hubble Space Telescope at 1.6 μm. We find that ∼ 50% of the Seyfert 2.0 galaxies which are part of the Revised Shapely-Ames (RSA) Catalog or the CfA redshift sample contain unresolved continuum sources at 1.6 μm. All but a couple of the Seyfert 1.0-1.9 galaxies display unresolved continuum sources. The unresolved sources have fluxes of order 1 mJy, near infrared luminosities of order 1041 ergs s-1, and absolute magnitudes MH ∼ -16. Comparison non-Seyfert galaxies from the RSA Catalog display significantly fewer (∼20%), somewhat lower luminosity nuclear sources, which could be due to compact star clusters. We find that the luminosities of the unresolved Seyfert 1.0-1.9 sources at 1.6 μm are correlated with [O III] λ15007 and hard X-ray luminosities, implying that these sources are nonstellar. Assuming a spectral energy distribution similar to that of a Seyfert 2 galaxy, we estimate that a few percent of local spiral galaxies contain black holes emitting as Seyferts at a moderate fraction, ∼10-1-10-4, of their Eddington luminosities. We find no strong correlation between 1.6 μm fluxes and hard X-ray or [O III] λ5007 fluxes for the pure Seyfert 2.0 galaxies. These galaxies also tend to have lower 1.6 μm luminosities compared to the Seyfert 1.0-1.9 galaxies of similar [O III] luminosity. Either large extinctions (AV ∼ 20-40) are present toward their continuumemitting regions or some fraction of the unresolved sources at 1.6 μ are compact star clusters. With increasing Seyfert type the fraction of unresolved sources detected at 1.6 μm and the ratio of 1.6 μm to [O III] fluxes tend to decrease. These trends are consistent with the unification model for Seyfert 1 and 2 galaxies.

AB - We examine 112 Seyfert galaxies observed by the Hubble Space Telescope at 1.6 μm. We find that ∼ 50% of the Seyfert 2.0 galaxies which are part of the Revised Shapely-Ames (RSA) Catalog or the CfA redshift sample contain unresolved continuum sources at 1.6 μm. All but a couple of the Seyfert 1.0-1.9 galaxies display unresolved continuum sources. The unresolved sources have fluxes of order 1 mJy, near infrared luminosities of order 1041 ergs s-1, and absolute magnitudes MH ∼ -16. Comparison non-Seyfert galaxies from the RSA Catalog display significantly fewer (∼20%), somewhat lower luminosity nuclear sources, which could be due to compact star clusters. We find that the luminosities of the unresolved Seyfert 1.0-1.9 sources at 1.6 μm are correlated with [O III] λ15007 and hard X-ray luminosities, implying that these sources are nonstellar. Assuming a spectral energy distribution similar to that of a Seyfert 2 galaxy, we estimate that a few percent of local spiral galaxies contain black holes emitting as Seyferts at a moderate fraction, ∼10-1-10-4, of their Eddington luminosities. We find no strong correlation between 1.6 μm fluxes and hard X-ray or [O III] λ5007 fluxes for the pure Seyfert 2.0 galaxies. These galaxies also tend to have lower 1.6 μm luminosities compared to the Seyfert 1.0-1.9 galaxies of similar [O III] luminosity. Either large extinctions (AV ∼ 20-40) are present toward their continuumemitting regions or some fraction of the unresolved sources at 1.6 μ are compact star clusters. With increasing Seyfert type the fraction of unresolved sources detected at 1.6 μm and the ratio of 1.6 μm to [O III] fluxes tend to decrease. These trends are consistent with the unification model for Seyfert 1 and 2 galaxies.

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KW - Galaxies: spiral

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