The Nuclear and Circumnuclear Stellar Population in Seyfert 2 Galaxies: Implications for the Starburst-Active Galactic Nucleus Connection

By R. G. González Delgado, T. Heckman, C. Leitherer. 2000

164 citations recorded by the source corpus.

We report the results of a spectroscopic investigation of a sample of 20 of the brightest type 2 Seyfert nuclei. Our goal is to search for the direct spectroscopic signature of massive stars and thereby probe the role of circumnuclear starbursts in the Seyfert phenomenon. The method used is based on the detection of the higher order Balmer lines and He I lines in absorption and the Wolf-Rayet feature at ~4680 Å in emission. These lines are strong indicators of the presence of young (a few Myr) and intermediate-age (a few 100 Myr) stellar populations. In over half the sample, we have detected He I and/or strong stellar absorption features in the high-order (near-UV) Balmer series together with relatively weak lines from an old stellar population. In three others we detect a broad emission feature near 4680 Å that is most plausibly ascribed to a population of Wolf-Rayet stars (the evolved descendants of the most massive stars). We therefore conclude that the blue and near-UV light of over half of the sample is dominated by young and/or intermediate age stars. The "young" Seyfert 2 galaxies have larger far-IR luminosities, cooler mid/far-IR colors, and smaller [O III]/Hβ flux ratios than the "old" ones. These differences are consistent with a starburst playing a significant energetic role in the former class. We consider the possibility that there may be two distinct subclasses of Seyfert 2 nuclei ("starbursts" and "hidden broadline regions" [BLRs]). However, the fact that hidden BLRs have been found in three of the "young" nuclei argues against this and suggests that nuclear starbursts may be a more general part of the Seyfert phenomenon.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/79881e2b2af947d1c3a7bda3fda5402a0fe7588d

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In Astronomy and Astrophysics

1. D. M. Alexander
2. P. Hopkins
3. L. Hernquist
4. H. Netzer
5. T. Heckman
6. R. Hickox
7. W. N. Brandt
8. D. Schneider

Citations in the corpus

• Candidate Type II Quasars from the Sloan Digital Sky Survey. I. Selection and Optical Properties of a Sample at 0.3 < Z < 0.83 (2003, result): “Traditionally it was thought that the starburst occurs on the subkiloparsec scales near the nucleus; this is supported by investigations of nearby Seyfert 2 galaxies showing circumnuclear starbursts with sizes of several hundred parsecs (González Delgado et al. 2001).”
• Spitzer Quasar and ULIRG Evolution Study (QUEST). I. The Origin of the Far-Infrared Continuum of QSOs (2006, background): “This extends to higher luminosity a similar result obtained by S02 on the basis of ISO spectroscopy of mostly lower luminosity Seyfert galaxies, and of a wide range of optical and near-infrared studies suggesting elevated starburst activity in Seyfert galaxies (e.g., Heckman et al. 1997; Oliva et al”
• ONGOING AND CO-EVOLVING STAR FORMATION IN zCOSMOS GALAXIES HOSTING ACTIVE GALACTIC NUCLEI (2008, methodology): “Fully consistent with this scheme, young stellar populations are known to be prevalent within the bulges of nearby Seyfert galaxies (e.g., Terlevich et al. 1990; González Delgado et al. 2001; Whittle & Nelson 2003) and luminous quasars (Jahnke et al. 2004a; Letawe et al. 2007).”
• On the origin of soft X-rays in obscured AGN: answers from high-resolution spectroscopy with XMM–Newton (2006, background): “Gas in the nuclear environment could be heated to million degrees by shocks induced by AGN outflows (King 2005) or episodes of intense star formation (Cid Fernandes et al. 1998; Gonzalez-Delgado et al. 2001).”
• What drives the growth of black holes (2011, background): “However, LINERs comprise a heterogenous mix of composite AGN– star-forming galaxies, optically obscured AGNs, lowluminosity AGNs, and early type galaxies without AGN activity (e.g., Binette et al., 1994; Ho et al., 2001, 2003; Eracleous et al., 2002; Satyapal et al., 2004; Kewley et al., 2006; Shiel”
• Resolving the mid-infrared cores of local Seyferts (2009, background): “The extended SB emission over the central arcsec, especially the central ‘horizontal-S’ shaped structu e of knots (cf. González Delgado et al. 1998) are clearly visible in the UV, but not at 12-µm. where Lν represent the monochromatic luminosities [erg s−1 Hz−1] at frequencies (ν) corresponding to ”
• The star formation history of Seyfert 2 nuclei (2004, background): “Another emblematic example is IC 5135 (NGC 7130), whose UV spectrum shows wind lines of massive stars and a logarithmic slope typical of dusty starbursts, with little or no sign of a power-law (González Delgado et al. 1998), while our synthesis yields xFC = 35%, xY = 34% and AV = 0.”
• A Close Look at Star Formation around Active Galactic Nuclei (2007, background): “…Seyferts, notably Seyfert 2 galaxies, since these are the closest examples (Sarzi et al. 2007; Asari et al. 2007; González Delgado & Cid Fernandes 2005; Cid Fernandes et al. 2004; González Delgado et al. 2001; Gu et al. 2001; Joguet et al. 2001; Storchi-Bergmann et al. 2001; Ivanov et al. 2000).”