Skip to main content


Author(s): Ludwig, Randi R.; Greene, Jenny E.; Barth, Aaron J.; Ho, Luis C.

To refer to this page use:
Abstract: We present spectroscopic observations of 27 active galactic nuclei (AGNs) with some of the lowest black hole (BH) masses known. We use the high spectral resolution and small aperture of our Keck data, taken with the Echellette Spectrograph and Imager, to isolate the narrow-line regions (NLRs) of these low-mass BHs. We investigate their emission-line properties and compare them with those of AGNs with higher-mass BHs. While we are unable to determine absolute metallicities, some of our objects plausibly represent examples of the low-metallicity AGNs described by Groves et al., based on their [NII]/H alpha ratios and their consistency with the Kewley & Ellison mass-metallicity relation. We find tentative evidence for steeper far-UV spectral slopes in lower-mass systems. Overall, NLR emission lines in these low-mass AGNs exhibit trends similar to those seen in AGNs with higher-mass BHs, such as increasing blueshifts and broadening with increasing ionization potential. Additionally, we see evidence of an intermediate-line region whose intensity correlates with L/L-Edd, as seen in higher-mass AGNs. We highlight the interesting trend that, at least in these low-mass AGNs, the [OIII] equivalent width (EW) is highest in symmetric NLR lines with no blue wing. This trend of increasing [OIII] EW with line symmetry could be explained by a high covering factor of lower-ionization gas in the NLR. In general, low-mass AGNs preserve many well-known trends in the structure of the NLR, while exhibiting steeper ionizing continuum slopes and somewhat lower gas-phase metallicities.
Publication Date: 1-Sep-2012
Electronic Publication Date: 14-Aug-2012
Citation: Ludwig, Randi R, Greene, Jenny E, Barth, Aaron J, Ho, Luis C. (2012). PHYSICAL PROPERTIES OF THE NARROW-LINE REGION OF LOW-MASS ACTIVE GALAXIES. ASTROPHYSICAL JOURNAL, 756, doi:10.1088/0004-637X/756/1/51
DOI: doi:10.1088/0004-637X/756/1/51
ISSN: 0004-637X
Related Item:
Pages: 1 - 17
Type of Material: Journal Article
Journal/Proceeding Title: ASTROPHYSICAL JOURNAL
Version: Final published version. Article is made available in OAR by the publisher's permission or policy.

Items in OAR@Princeton are protected by copyright, with all rights reserved, unless otherwise indicated.