Abstract
We have explored the relationship between the [O III] λ5007 and the 2-10 keV luminosities for a sample of broad- and narrow-line Seyfert 1 galaxies (BLSy1s and NLSy1s, respectively). We find that both types of Seyfert galaxies span the same range in luminosity and possess similar [O III]/X-ray ratios. The NLSy1s are more luminous than BLSy1s when normalized to their central black hole masses, a fact attributed to higher mass accretion rates. However, we find no evidence for elevated [O III]/X-ray ratios in NLSy1s, which would have been expected if they had excess extreme-ultraviolet (EUV) continuum emission compared to BLSy1s. Also, other studies suggest that the gas in narrow-line regions (NLRs) of NLSy1s and BLSy1s spans a similar range in ionization, contrary to what is expected if those of the former are exposed to a stronger flux of EUV radiation. The simplest interpretation is that, like BLSy1s, a large EUV bump is not present in NLSy1s. However, we show that the [O III] /X-ray ratio can be lowered as a result of absorption of the ionizing continuum by gas close to the central source, although there is no evidence that intrinsic line-of-sight absorption is more common among NLSy1s, as would be expected if there were a larger amount of circumnuclear gas. Other possible explanations include (1) anisotropic emission of the ionizing radiation; (2) higher gas densities in the NLRs of NLSy1s, resulting in lower average ionization; or (3) the presence of strong winds in the nuclei of NLSy1s that may drive off much of the gas in the NLR, resulting in lower cover fraction and weaker [O III] emission.
| Original language | English |
|---|---|
| Pages (from-to) | 794-799 |
| Number of pages | 6 |
| Journal | Astrophysical Journal |
| Volume | 607 |
| Issue number | 2 I |
| DOIs | |
| State | Published - Jun 1 2004 |
| Externally published | Yes |
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All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics
- Space and Planetary Science
Cite this
On the relationship between the optical emission-line and X-ray luminosities in seyfert 1 galaxies. / Kraemer, S. B.; George, I. M.; Crenshaw, D. M.; Gabel, Jack.
In: Astrophysical Journal, Vol. 607, No. 2 I, 01.06.2004, p. 794-799.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - On the relationship between the optical emission-line and X-ray luminosities in seyfert 1 galaxies
AU - Kraemer, S. B.
AU - George, I. M.
AU - Crenshaw, D. M.
AU - Gabel, Jack
PY - 2004/6/1
Y1 - 2004/6/1
N2 - We have explored the relationship between the [O III] λ5007 and the 2-10 keV luminosities for a sample of broad- and narrow-line Seyfert 1 galaxies (BLSy1s and NLSy1s, respectively). We find that both types of Seyfert galaxies span the same range in luminosity and possess similar [O III]/X-ray ratios. The NLSy1s are more luminous than BLSy1s when normalized to their central black hole masses, a fact attributed to higher mass accretion rates. However, we find no evidence for elevated [O III]/X-ray ratios in NLSy1s, which would have been expected if they had excess extreme-ultraviolet (EUV) continuum emission compared to BLSy1s. Also, other studies suggest that the gas in narrow-line regions (NLRs) of NLSy1s and BLSy1s spans a similar range in ionization, contrary to what is expected if those of the former are exposed to a stronger flux of EUV radiation. The simplest interpretation is that, like BLSy1s, a large EUV bump is not present in NLSy1s. However, we show that the [O III] /X-ray ratio can be lowered as a result of absorption of the ionizing continuum by gas close to the central source, although there is no evidence that intrinsic line-of-sight absorption is more common among NLSy1s, as would be expected if there were a larger amount of circumnuclear gas. Other possible explanations include (1) anisotropic emission of the ionizing radiation; (2) higher gas densities in the NLRs of NLSy1s, resulting in lower average ionization; or (3) the presence of strong winds in the nuclei of NLSy1s that may drive off much of the gas in the NLR, resulting in lower cover fraction and weaker [O III] emission.
AB - We have explored the relationship between the [O III] λ5007 and the 2-10 keV luminosities for a sample of broad- and narrow-line Seyfert 1 galaxies (BLSy1s and NLSy1s, respectively). We find that both types of Seyfert galaxies span the same range in luminosity and possess similar [O III]/X-ray ratios. The NLSy1s are more luminous than BLSy1s when normalized to their central black hole masses, a fact attributed to higher mass accretion rates. However, we find no evidence for elevated [O III]/X-ray ratios in NLSy1s, which would have been expected if they had excess extreme-ultraviolet (EUV) continuum emission compared to BLSy1s. Also, other studies suggest that the gas in narrow-line regions (NLRs) of NLSy1s and BLSy1s spans a similar range in ionization, contrary to what is expected if those of the former are exposed to a stronger flux of EUV radiation. The simplest interpretation is that, like BLSy1s, a large EUV bump is not present in NLSy1s. However, we show that the [O III] /X-ray ratio can be lowered as a result of absorption of the ionizing continuum by gas close to the central source, although there is no evidence that intrinsic line-of-sight absorption is more common among NLSy1s, as would be expected if there were a larger amount of circumnuclear gas. Other possible explanations include (1) anisotropic emission of the ionizing radiation; (2) higher gas densities in the NLRs of NLSy1s, resulting in lower average ionization; or (3) the presence of strong winds in the nuclei of NLSy1s that may drive off much of the gas in the NLR, resulting in lower cover fraction and weaker [O III] emission.
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U2 - 10.1086/383529
DO - 10.1086/383529
M3 - Article
VL - 607
SP - 794
EP - 799
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 2 I
ER -