Quasi‐Stellar Objects, Ultraluminous Infrared Galaxies, and Mergers

Canalizo, Gabriela; Stockton, Alan

doi:10.1086/321520

Cited by 346 publications

(473 citation statements)

References 144 publications

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“…In this sense, strong interactions and mergers are the mechanisms responsible for the funneling of gas into the central regions of galaxies, which subsequently may feed both star formation and AGN activity. Although some aspects of this scenario are still controversial, observations confirm the connection between QSOs, ULIRGs, and mergers (Canalizo & Stockton 2001 and references therein). In Note.-Fraction of light inside the slit for all the observational configurations.…”

Section: Constraining the Agn Contributionmentioning

confidence: 99%

A Multiwavelength Approach to the Star Formation Rate Estimation in Galaxies at Intermediate Redshifts

Cardiel

Elbaz

Schiavon

et al. 2003

ApJ

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We use a sample of seven starburst galaxies at intermediate redshifts (z $ 0:4 and 0.8) with observations ranging from the observed ultraviolet to 1.4 GHz, to compare the star formation rate (SFR) estimators that are used in the different wavelength regimes. We find that extinction-corrected H underestimates the SFR, and the degree of this underestimation increases with the infrared luminosity of the galaxies. Galaxies with very different levels of dust extinction as measured with SFR IR /SFR(H , uncorrected for extinction) present a similar attenuation A[H ], as if the Balmer lines probed a different region of the galaxy than the one responsible for the bulk of the IR luminosity for large SFRs. In addition, SFR estimates derived from [O ii] 3727 match very well those inferred from H after applying the metallicity correction derived from local galaxies. SFRs estimated from the UV luminosities show a dichotomic behavior, similar to that previously reported by other authors in galaxies at zd0:4. Here we extend this result up to z $ 0:8. Finally, one of the studied objects is a luminous compact galaxy (LCG) that may be suffering similar dust-enshrouded star formation episodes. These results highlight the relevance of quantifying the actual L IR of LCGs, as well as that of a much larger and generic sample of luminous infrared galaxies, which will be possible after the launch of SIRTF.

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Section: Constraining the Agn Contributionmentioning

confidence: 99%

A Multiwavelength Approach to the Star Formation Rate Estimation in Galaxies at Intermediate Redshifts

Cardiel

Elbaz

Schiavon

et al. 2003

ApJ

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“…Also several Seyfert galaxies and QSO hosts display such signatures, and age dating of their stellar population (e.g., González Delgado et al 2001;Canalizo & Stockton 2001) is strongly suggestive of an earlier, interaction-induced starburst phase, which produces and drives the fueling of the nuclear activity (Sanders et al 1988;Barthel 2001). We observe no signs of this connection in the hot BLRGs.…”

Section: L24mentioning

confidence: 99%

Broad-line radio galaxies: Old and feeble?

Bemmel¹,

Barthel²

2001

A&A

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Abstract. Far-infrared photometry of broad-line radio galaxies shows this class of AGN to consist of many hot and some cool infrared emitters, with peaks in their spectral energy distributions around 25 µm or longward of 60 µm, respectively. Quantitative analysis indicates that this distribution relates to a substantial dispersion in the strength of the cool dust component: broad-line radio galaxies are relatively poor in large-scale dust. Possibly they have undergone a different merger evolution, or are relatively old AGN.

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“…Their properties probably depend on both orientation and evolution effects (Richards et al 2011;Allen et al 2011). Based on the shape of the continuum in the UV and X-rays and on the BAL fraction in the infrared, it has been suggested that FeLoBAL quasars in particular probe a much more obscured quasar population than non-BAL quasars and may represent a young evolutionary stage when a thick shroud of gas and dust is being expelled from the central region of the AGN (Voit et al 1993;Becker et al 1997;Canalizo & Stockton 2001;Lípari et al 2009;Dai et al 2010;Farrah et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Unusual quasars from the Sloan Digital Sky Survey selected by means of Kohonen self-organising maps

Meusinger¹,

Schalldach²,

Scholz³

et al. 2012

A&A

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Context. Large spectroscopic surveys have discovered very peculiar and hitherto unknown types of active galactic nuclei (AGN). Such rare objects may hold clues to the accretion history of the supermassive black holes at the centres of galaxies. Aims. We aim to create a sizeable sample of unusual quasars from the unprecedented spectroscopic database of the Sloan Digital Sky Survey (SDSS). Methods. We exploit the spectral archive of the SDSS Data Release 7 to select unusual quasar spectra. The selection method is based on a combination of the power of self-organising maps and the visual inspection of a huge number of spectra. Self-organising maps were applied to nearly 10 5 spectra classified as quasars at redshifts from z = 0.6 to 4.3 by the SDSS pipeline. Particular attention was paid to minimise possible contamination by rare peculiar stellar spectral types. All selected quasar spectra were individually studied to determine the object type and the redshift.Results. We present a catalogue of 1005 quasars with unusual spectra. These spectra are dominated by either broad absorption lines (BALs; 42%), unusual red continua (27%), weak emission lines (18%), or conspicuously strong optical and/or UV iron emission (11%). This large sample provides a useful resource for both studying properties and relations of/between different types of unusual quasars and selecting particularly interesting objects, even though the compilation is not aimed at completeness in a quantifiable sense. The spectra are grouped into six types for which composite spectra are constructed and mean properties are computed. Remarkably, all these types turn out to be on average more luminous than comparison samples of normal quasars after a statistical correction is made for intrinsic reddening (E(B − V) ≈ 0 to 0.4 for SMC-like extinction). Both the unusual BAL quasars and the strong iron emitters have significantly lower radio luminosities than normal quasars. We also confirm that strong BALs avoid the most radioluminous quasars. For 32 particularly interesting objects, individual spectra are presented. Among these objects are quasars with many narrow BAL troughs and one quasar where the continuum is strongly suppressed by overlapping BAL troughs across nearly the whole SDSS spectrum. Finally, we create a sample of quasars similar to the two "mysterious" objects discovered by Hall et al. (2002, ApJS, 141, 267) and briefly discuss the quasar properties and possible explanations of their highly peculiar spectra.

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Quasi‐Stellar Objects, Ultraluminous Infrared Galaxies, and Mergers

Cited by 346 publications

References 144 publications

A Multiwavelength Approach to the Star Formation Rate Estimation in Galaxies at Intermediate Redshifts

A Multiwavelength Approach to the Star Formation Rate Estimation in Galaxies at Intermediate Redshifts

Broad-line radio galaxies: Old and feeble?

Unusual quasars from the Sloan Digital Sky Survey selected by means of Kohonen self-organising maps

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