scholarly journals Environments of dwarf galaxies with optical AGN characteristics

2020 ◽  
Vol 496 (3) ◽  
pp. 2577-2590 ◽  
Author(s):  
Mikkel T Kristensen ◽  
Kevin Pimbblet ◽  
Samantha Penny
Keyword(s):  
Emission Line ◽  
Active Galactic Nuclei ◽  
Dwarf Galaxies ◽  
Galactic Nuclei ◽  
Local Environment ◽  
Selection Method ◽  
Estimation Methods ◽  
Selection Methods ◽  
Low Mass ◽  
Future Work

ABSTRACT This study aims to explore the relation between dwarf galaxies (M* ≤ 5 × 109 M⊙) with active galactic nuclei (AGNs) and their environment by comparing neighbourhood parameters of AGN and non-AGN samples. Using the NASA-Sloan Atlas, both the local environment and the immediate environment of dwarf galaxies with z ≤ 0.055 are analysed. Of the 145 155 galaxies in the catalogue, 62 258 of them are classified as dwarf galaxies, and by employing two AGN selection methods based on emission-line fluxes (BPT and WHAN), 4476 are found to have AGN characteristics in their optical spectra. Regardless of selection method, this study finds no discernible differences in environment between AGN and non-AGN host dwarf galaxies and these results indicate that environment is not an important factor in triggering AGN activity in dwarf galaxies. This is in line with existing literature on environments of regular galaxies with AGNs and suggests universality in terms of reaction to environment across the mass regime. The biases of AGN selection in low-mass galaxies, and the biases of different measures of environment are also considered. It is found that there are several mass trends in emission-line ratios and that the SDSS fibre covers galaxies non-uniformly with redshift. These biases should be accounted for in future work by possibly including other wavelength regimes or mass weighting of emission-line ratios. Lastly, a discussion of the environment estimation methods is included since they may not gauge the desired properties due to factors such as time delay or using loosely constrained proxy parameters.

scholarly journals A search for H2O masers in 100 active dwarf galaxies

2020 ◽  
Vol 499 (1) ◽  
pp. 1233-1249
Author(s):  
M J Rosenthal ◽  
I Zaw
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Detection Rate ◽  
Dwarf Galaxies ◽  
Galactic Nuclei ◽  
Optical Emission ◽  
Massive Black Hole ◽  
Massive Galaxies ◽  
Low Mass ◽  
Green Bank Telescope

ABSTRACT We present the results of the first dedicated survey for 22 GHz H2O maser emission in dwarf galaxies outside of the Local Group, with the aim of discovering disc masers. Studies of disc masers yield accurate and precise measurements of black hole (BH) mass, and such measurements in dwarf galaxies would be key to understanding the low-mass end of BH–galaxy coevolution. We used the Green Bank Telescope to survey 100 nearby (z ≲ 0.055) dwarf galaxies (M* ≲ 109.5 M⊙) with optical emission line ratios indicative of accretion on to a massive black hole. We detected no new masers down to a limit of ∼12 mJy (5σ). We compared the properties of our sample with those of ∼1850 known detections and non-detections in massive galaxies. We find, in agreement with previous studies, that masers are preferentially hosted by Seyferts and highly obscured, [O iii]-bright active galactic nuclei (AGNs). Our sample has fewer Seyferts, is less obscured, and is [O iii]-faint. Though the overall maser detection rate is ∼3 per cent in massive galaxies, the predicted rate for our sample, weighted by its optical properties, is ∼0.6–1.7 per cent, corresponding to a probability of making no detections of ∼20–50 per cent. We also found a slight increase in the detection rate with increased stellar mass in previously surveyed galaxies. However, further observations are required to discern whether there is an intrinsic difference between the maser fraction in active dwarf galaxies and in their massive counterparts for the same AGN properties.

scholarly journals CHANDRAAND MMT OBSERVATIONS OF LOW-MASS BLACK HOLE ACTIVE GALACTIC NUCLEI ACCRETING AT LOW RATES IN DWARF GALAXIES

2014 ◽  
Vol 782 (1) ◽  
pp. 55 ◽  
Author(s):  
W. Yuan ◽  
H. Zhou ◽  
L. Dou ◽  
X.-B. Dong ◽  
X. Fan ◽  
...  
Keyword(s):  
Black Hole ◽  
Active Galactic Nuclei ◽  
Dwarf Galaxies ◽  
Galactic Nuclei ◽  
Low Mass

scholarly journals A systematic survey for z< 0.04 CLAGNs

2021 ◽  
Vol 503 (2) ◽  
pp. 2583-2597
Author(s):  
Madhooshi R Senarath ◽  
Michael J I Brown ◽  
Michelle E Cluver ◽  
Thomas H Jarrett ◽  
Christian Wolf ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Selection Method ◽  
Selection Methods ◽  
Small Aperture ◽  
Systematic Survey ◽  
The Past ◽  
Spectral Class ◽  
Dust Component ◽  
Over Time

ABSTRACT We have conducted a systematic survey for z &lt; 0.04 active Galactic nuclei (AGNs) that may have changed spectral class over the past decade. We use SkyMapper, Pan-STARRS and the Véron-Cetty & Véron catalogue to search the entire sky for these ‘changing-look’ AGNs (CLAGNs) using a variety of selection methods, where Pan-STARRS has a coverage of 3$\pi$ steradians (sky north of Declination −30○) and SkyMapper has coverage of ∼21000 $~\rm {deg^2}$ (sky south of Declination 0○). We use small aperture photometry to measure how colour and flux have changed over time, where a change may indicate a change in spectral type. Optical colour and flux are used as a proxy for changing Hα equivalent width, while WISE 3.4 μm flux is used to look for changes in the hot dust component. We have identified four AGNs with varying spectra selected using our optical colour selection method. Three AGNs were confirmed from recent observations with WiFeS on the 2.3 m telescope at Siding Spring and the other was identified from archival spectra alone. From this, we identify two new CLAGNs; NGC 1346 and 2MASX J20075129–1108346. We also recover Mrk 915 and Mrk 609, which are known to have varying spectra in the literature, but they do not meet our specific criteria for CLAGNs.

scholarly journals Constraints on the production and escape of ionizing radiation from the emission-lines of metal-poor star-forming galaxies

2019 ◽  
Vol 15 (S352) ◽  
pp. 121-122
Author(s):  
A. Plat ◽  
S. Charlot ◽  
G. Bruzual ◽  
A. Feltre ◽  
A. Vidal-Garca ◽  
...  
Keyword(s):  
Ionizing Radiation ◽  
Emission Line ◽  
Active Galactic Nuclei ◽  
High Redshift ◽  
Galactic Nuclei ◽  
Emission Lines ◽  
High Redshift Galaxies ◽  
Star Forming ◽  
Radiative Shocks ◽  
Metal Poor Star

AbstractTo understand how the nature of the ionizing sources and the leakage of ionizing photons in high-redshift galaxies can be constrained from their emission-line spectra, we compare emission-line models of star-forming galaxies including leakage of ionizing radiation, active galactic nuclei (AGN) and radiative shocks, with observations of galaxies at various redshifts with properties expected to approach those of primeval galaxies.

scholarly journals NEON AND $[{\rm{C}}\,{\rm{II}}]$ 158 μ m EMISSION LINE PROFILES IN DUSTY STARBURSTS AND ACTIVE GALACTIC NUCLEI

2016 ◽  
Vol 226 (1) ◽  
pp. 11 ◽  
Author(s):  
Anahit Samsonyan ◽  
Daniel Weedman ◽  
Vianney Lebouteiller ◽  
Donald Barry ◽  
Lusine Sargsyan
Keyword(s):  
Emission Line ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Line Profiles

scholarly journals Molecular hydrogen and [Fe ii] in active galactic nuclei – III. Low-ionization nuclear emission-line region and star-forming galaxies

2013 ◽  
Vol 430 (3) ◽  
pp. 2002-2017 ◽  
Author(s):  
R. Riffel ◽  
A. Rodríguez-Ardila ◽  
I. Aleman ◽  
M. S. Brotherton ◽  
M. G. Pastoriza ◽  
...  
Keyword(s):  
Emission Line ◽  
Active Galactic Nuclei ◽  
Molecular Hydrogen ◽  
Galactic Nuclei ◽  
Star Forming ◽  
Line Region

scholarly journals Velocity Diagnostics of the Broad Emission-Line Region of Active Galactic Nuclei

1997 ◽  
Vol 159 ◽  
pp. 175-178 ◽  
Author(s):  
Brian Espey
Keyword(s):  
Emission Line ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Nuclear Region ◽  
Driving Mechanisms ◽  
Broad Emission ◽  
Line Region ◽  
Broad Emission Line ◽  
Ongoing Project

AbstractWe present a brief review of emission-line velocity differences, and describe an ongoing project to determine the driving mechanisms responsible. We conclude with a brief outline of the use of velocity differences as probes of the conditions in the nuclear region of AGNs.

scholarly journals Structure and Emission Line Spectrum of an X-ray Heated Accretion Disk in AGN

1994 ◽  
Vol 159 ◽  
pp. 484-484
Author(s):  
Yuan-Kuen Ko ◽  
Timothy R. Kallman
Keyword(s):  
Emission Line ◽  
Active Galactic Nuclei ◽  
Accretion Disk ◽  
Line Emission ◽  
Galactic Nuclei ◽  
X Ray ◽  
Disk Size ◽  
Emission Line Spectrum ◽  
Self Gravity ◽  
A Site

We investigate the structure of an X-ray heated accretion disk in active galactic nuclei. It is found that X-ray heating can prevent the disk to be disrupted by its self-gravity under sufficient X-ray heating. The disk size can be two orders of magnitute larger than that limited by self-gravity of the disk without X-ray heating. An accretion disk corona will be formed by X-ray heating and can be a site for line emission. We present such emission line spectra which range from optical to hard X-ray energies and compare with the observational data.

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