Empirical Diagnostics of the Starburst-AGN Connection

By R. C. Fernandes, T. Heckman, H. R. Schmitt, R. Delgado, T. Storchi-Bergmann. 2001

143 citations recorded by the source corpus.

We examine a representative sample of 35 Seyfert 2 nuclei. Previous work has shown that nearly half (15) of these nuclei show the direct (but difficult to detect) spectroscopic signature at optical/near-UV wavelengths of the hot massive stars that power circumnuclear starbursts. In the present paper we examine a variety of more easily measured quantities for this sample, such as the equivalent widths of strong absorption features, continuum colors, emission line equivalent widths, emission line ratios and profiles, far-IR luminosities, and near-UV surface brightness. We compare the composite starburst + Seyfert 2 nuclei to "pure" Seyfert 2 nuclei, Starburst galaxies, and normal galactic nuclei. Our goals are to verify whether the easily measured properties of the composite nuclei are consistent with the expected impact of a starburst and to investigate alternative less demanding methods to infer the presence of starbursts in Seyfert 2 nuclei, applicable to larger or more distant samples. We show that starbursts do indeed leave clear and easily quantifiable imprints on the near-UV to optical continuum and emission line properties of Seyfert 2's. Composite starburst + Seyfert 2 systems can be recognized by: (1) a strong "featureless continuum" (FC), which dilutes the Ca II K line from old stars in the host's bulge to an equivalent width WK < 10 Å; (2) emission lines whose equivalent widths are intermediate between starburst galaxies and "pure" Seyfert 2's; (3) relatively low excitation line ratios, which indicate that part of the gas ionization in these Seyfert 2's (typically ~50% of Hβ) is due to photoionization by OB stars; (4) large far-IR luminosities (≳1010 L☉); (5) high near-UV surface brightness (~103 L☉ pc-2). These characteristics are all consistent with the expected impact of circumnuclear starbursts on the observed properties of Seyfert 2's. Furthermore, they offer alternative empirical diagnostics of the presence of circumnuclear starbursts from a few easily measured quantities.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/2704b58de71b06fda8e5eeee35db2544ca5905a3

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In Astronomy and Astrophysics

1. P. Hopkins
2. L. Hernquist
3. T. Heckman
4. Luis C. Ho
5. D. Schneider
6. P. Best
7. C. Conroy
8. Jenny E. Greene

Citations in the corpus

• A Hubble Space Telescope Survey of Extended [O III] λ5007 Å Emission in a Far-Infrared-Selected Sample of Seyfert Galaxies: Results (2003, background): “…have circumnuclear starbursts (Heckman et al. 1997; Cid Fernandes, StorchiBergmann & Schmitt 1998; Schmitt, Storchi-Bergmann & Cid Fernandes 1999; González Delgado, Heckman & Leitherer 2001; Cid Fernandes et al. 2001), this effect should also be important in the determination of their NLR sizes.”
• Semi‐empirical analysis of Sloan Digital Sky Survey galaxies – III. How to distinguish AGN hosts (2006, background): “Naturally, young stars can be associated with an AGN, in which case they are often mistaken for a featureless, non-stellar continuum (Cid Fernandes et al. 2001, 2004).”
• The Coevolution of Galaxies and Supermassive Black Holes: Insights from Surveys of the Contemporary Universe (2014, background): “Other authors have proposed further refinements of this division (e.g. Stasinska et al. 2006, Kewley et al. 2006, Cid Fernandes et al. 2011).”
• Galaxy pairs in the Sloan Digital Sky Survey - IV: Interactions trigger AGN (2011, background): “Indeed, there is an observational link between enhanced central star formation rates and black hole activity that extends beyondmergers to the general galaxy population (Cid-Fernandes et al. 2001; Kauffmann et al. 2003a; Silverman et al. 2009; Reichard et al. 2009).”
• The Star-forming Torus and Stellar Dynamical Black Hole Mass in the Seyfert 1 Nucleus of NGC 3227 (2006, background): “In particular empirical population synthesis of Seyfert 2 nuclei (Cid Fernandes et al. 2001; González Delgado, et al. 2001; Storchi-Bergmann et al. 2001) reveals evidence for recent (<1Gyr) star formation within a few hundred parsecs of the nuclei in about 40% of Seyfert 2 nuclei.”
• Evolutionary stellar population synthesis at high spectral resolution: optical wavelengths (2005, background): “…obtained at intermediate spectral resolution in the last few years to date the stellar population (González Delgado, Heckman, & Leitherer 2001; Cid Fernandes et al. 2001; Aretxaga et al. 2001; Kauffmann et al. 2003a,b,c; Cid Fernandes et al. 2004; González Delgado et al. 2004; Tadhunter et al.…”
• The host galaxies of active galactic nuclei (2003, unknown): “The stellar populations in the nuclei of weak AGN are predominantly old (e.g. Ho et al. 2003), while a young stellar population is clearly present in about half of powerful type 2 Seyfert nuclei (e.g. Cid Fernandes et al. 2001; Joguet et al. 2001).”
• Bimodal gas accretion in the Horizon–MareNostrum galaxy formation simulation (2008, background): “This observation is further supported by the analysis of spectroscopic data, using star formation history reconstruction methods (Reichardt et al. 2001; Panter et al. 2003; Cid Fernandes et al. 2004; Ocvirk et al. 2006b,a).”
• 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, background): “Press) Blanton, M. R., Lupton, R. H., Maley, F. M., Young, N., Zehavi, I., & Loveday, J. 2003, AJ, 125, 2276 Boroson, T. A., &Green, R. F. 1992, ApJS, 80, 109 Cid Fernandes, R., Heckman, T., Schmitt, H., González Delgado, R. M., & Storchi-Bergmann, T. 2001, ApJ, 558, 81 Cid Fernandes, R., & Terlevi”
• The history of star-forming galaxies in the Sloan Digital Sky Survey (2007, background): “Z⋆ plane constrained by chemical evolution arguments (see also Schmidt et al. 1991; Bica et al. 1994; Cid Fernandes et al. 2001).”
• Evidence for Quasar Activity Triggered by Galaxy Mergers in HST Observations of Dust-reddened Quasars (2007, background): “The existence of a link between AGNs and starbursts/ ultraluminous infrared galaxies (ULIRGs) in the local universe has been discussed for a long time (e.g., Heckman et al. 1989; Sanders & Mirabel 1996; Cid Fernandes et al. 2001).”
• Emission-line diagnostics of low-metallicity active galactic nuclei (2006, background): “Although part of the spheroid growth mayresult from mergers of stellar disks (eg Kauffmann & Haehnelt 2000), star formation in the central regions of the galaxy is also expected to contribute to the overall growth of the bulge (Schmitt et al. 1999; Cid Fernandes et al. 2001, 2004).”
• Galaxy Zoo: Passive Red Spirals . (2009, methodology): “We test this by using emission line diagnostic diagrams (Baldwin Phillips & Terlevich 1981, hereafter BPT; Veilleux & Osterbrock 1987; Kewley et al. 2001, 2006; Cid Fernandes et al. 2001) to probe the dominant source of ionisation in the red and blue spiral galaxies.”
• Size and properties of the narrow-line region in Seyfert-1 galaxies from spatially-resolved optical spectroscopy (2006, result): “This hints the existence of a nuclear starburst as is confirmed by the stellar population synthesis of Cid Fernandes et al. (1998) and the results of StorchiBergmann et al. (2000): They describe ESO 362-G008 as relatively evolved nuclear starburst due to its high order Balmer absorption lines.”
• The star formation history of Seyfert 2 nuclei (2004, methodology): “The net effect is that, for practical purposes, the base becomes linearly dependent, such that a given component is well reproduced by linear combinations of others, as extensively discussed by Cid Fernandes et al. (2001b).”