Spitzer IRS Observations of Low-Mass Seyfert Galaxies

The Sloan Digital Sky Survey has made it possible to identify the first samples of active galaxies with estimated black hole masses below ~ 106M⊙. We have obtained Spitzer IRS low-resolution spectra, covering 5–38 μm, of a sample of 41 Seyfert galaxies with low-mass black holes. Our sample includes SDSS-selected objects from the low-mass Seyfert 1 sample of Greene & Ho (2004) and the low-mass Seyfert 2 sample of Barth et al. (2008), as well as NGC 4395 and POX 52. The goals of this work are to examine the dust emission properties of these objects and investigate the relationship between type 1 and type 2 AGNs at low luminosities and low masses, to search for evidence of star formation, and to use emission-line diagnostics to constrain physical conditions within the narrow-line regions. Here we present preliminary results from this project.

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Evidence for obscured broad [O iii] components in Type-2 AGN

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab185 ◽

2021 ◽

Vol 502 (2) ◽

pp. 2508-2512

Author(s):

Xue-Guang Zhang

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Unified Model ◽

Sloan Digital Sky Survey ◽

The Core ◽

Large Samples ◽

Sky Survey ◽

Narrow Emission

ABSTRACT In the manuscript, we report evidence on broad [O iii] components apparently obscured in Type-2 active galactic nuclei (AGN) under the framework of the unified model, after checking properties of broad [O iii] emissions in large samples of Type-1 and Type-2 AGN in Sloan Digital Sky Survey DR12. We can well confirm the statistically lower flux ratios of the broad to the core [O iii] components in Type-2 AGN than in Type-1 AGN, which can be naturally explained by stronger obscured broad [O iii] components by central dust torus in Type-2 AGN, unless the unified model for AGN was not appropriate to the narrow emission lines. The results provide further evidence to support broad [O iii] components coming from emission regions nearer to central BHs, and also indicate the core [O iii] component as the better indicator for central activities in Type-2 AGN, due to few effects of obscuration on the core [O iii] component. Considering the broad [O iii] components as signs of central outflows, the results provide evidence for strong central outflows being preferentially obscured in Type-2 AGN. Furthermore, the obscured broad [O iii] component can be applied to explain the different flux ratios of [O iii]λ5007Å/H β between Type-1 and Type-2 AGN in the BPT diagram.

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AGN torus properties with WISE

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314003317 ◽

2013 ◽

Vol 9 (S304) ◽

pp. 56-60

Author(s):

Robert Nikutta ◽

Maia Nenkova ◽

Željko Ivezić ◽

Nicholas Hunt-Walker ◽

Moshe Elitzur

Keyword(s):

Color Space ◽

Sloan Digital Sky Survey ◽

Wide Field ◽

Sky Survey ◽

Very Large Database ◽

First Time ◽

Previous Identification ◽

Infrared Survey

AbstractThe Wide-field Infrared Survey Explorer (WISE) has scanned the entire sky with unprecedented sensitivity in four infrared bands, at 3.4, 4.6, 12, and 22 μm. The WISE Point Source Catalog contains more than 560 million objects, among them hundreds of thousands of galaxies with Active Nuclei (AGN). While type 1 AGN, owing to their bright and unobscured nature, are easy to detect and constitute a rather complete and unbiased sample, their type 2 counterparts, postulated by AGN unification, are not as straightforward to identify. Matching the WISE catalog with known QSOs in the Sloan Digital Sky Survey we confirm previous identification of the type 1 locus in the WISE color space. Using a very large database of the popular Clumpy torus models, we find the colors of the putative type 2 counterparts, and also, for the first time, predict their number vs. flux relation that can be expected to be observed in any given WISE color range. This will allow us to put statistically very significant constraints on the torus parameters. Our results are a successful test of the AGN unification scheme.

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Are sdAs helium core stars?

Open Astronomy ◽

10.1515/astro-2017-0433 ◽

2017 ◽

Vol 26 (1) ◽

Cited By ~ 4

Author(s):

Ingrid Pelisoli ◽

S. O. Kepler ◽

Detlev Koester

Keyword(s):

Main Sequence ◽

Galactic Disk ◽

Physical Nature ◽

Sloan Digital Sky Survey ◽

Distance Modulus ◽

Main Sequence Stars ◽

Sky Survey ◽

Balmer Lines ◽

Low Mass ◽

Binary Evolution

AbstractEvolved stars with a helium core can be formed by non-conservative mass exchange interaction with a companion or by strong mass loss. Their masses are smaller than 0.5 M⊙. In the database of the Sloan Digital Sky Survey (SDSS), there are several thousand stars which were classified by the pipeline as dwarf O, B and A stars. Considering the lifetimes of these classes on the main sequence, and their distance modulus at the SDSS bright saturation, if these were common main sequence stars, there would be a considerable population of young stars very far from the galactic disk. Their spectra are dominated by Balmer lines which suggest effective temperatures around 8 000-10 000 K. Several thousand have significant proper motions, indicative of distances smaller than 1 kpc. Many show surface gravity in intermediate values between main sequence and white dwarf, 4.75 < log g < 6.5, hence they have been called sdA stars. Their physical nature and evolutionary history remains a puzzle. We propose they are not H-core main sequence stars, but helium core stars and the outcomes of binary evolution. We report the discovery of two new extremely-low mass white dwarfs among the sdAs to support this statement.

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White Dwarf Stars

International Journal of Modern Physics Conference Series ◽

10.1142/s2010194517600230 ◽

2017 ◽

Vol 45 ◽

pp. 1760023

Author(s):

S. O. Kepler ◽

Alejandra Daniela Romero ◽

Ingrid Pelisoli ◽

Gustavo Ourique

Keyword(s):

White Dwarf ◽

Final Stage ◽

White Dwarfs ◽

Sloan Digital Sky Survey ◽

Dwarf Stars ◽

Multiple Systems ◽

White Dwarf Stars ◽

Sky Survey ◽

Data Release ◽

Low Mass

White dwarf stars are the final stage of most stars, born single or in multiple systems. We discuss the identification, magnetic fields, and mass distribution for white dwarfs detected from spectra obtained by the Sloan Digital Sky Survey up to Data Release 13 in 2016, which lead to the increase in the number of spectroscopically identified white dwarf stars from 5[Formula: see text]000 to 39[Formula: see text]000. This number includes only white dwarf stars with [Formula: see text], i.e., excluding the Extremely Low Mass white dwarfs, which are necessarily the byproduct of stellar interaction.

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CO in Seyfert Galaxies

Symposium - International Astronomical Union ◽

10.1017/s0074180900141348 ◽

1989 ◽

Vol 134 ◽

pp. 359-364

Author(s):

Timothy M. Heckman

Keyword(s):

Seyfert Galaxies ◽

Normal Galaxies ◽

Line Widths ◽

Co Emission

We present data for Seyfert and normal galaxies in the Revised Shapley-Ames Catalog. The type 2 Seyferts are stronger CO and Far-IR emitters (by factors of 2–4) than either normal galaxies or type 1 Seyferts. The Seyfert CO line-widths correlate with both the 21cm HI and [OIII]5007 line-widths. Interferometer maps show that in many Seyferts the CO emission is strongly concentrated within radii of 100–1000pc of the nucleus. The implications of these results are briefly discussed.

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A VO study of SDSS AGNs with X-ray emission from ROSAT-PSPC pointed observations

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307011799 ◽

2006 ◽

Vol 2 (14) ◽

pp. 581-581

Author(s):

Robert J. Hanisch ◽

Anatoly A. Suchkov ◽

Timothy M. Heckman ◽

Wolfgang H. Voges

Keyword(s):

Survey Data ◽

Sloan Digital Sky Survey ◽

Radio Sources ◽

X Ray ◽

Sky Survey ◽

Data Release

We use VO facilities to study AGNs with X-ray emission. We present a sample of 1744 of Type 1 AGNs from the Sloan Digital Sky Survey Data Release 4 (SDSS DR4) spectroscopic catalog with X-ray counterparts in the White-Giommi-Angelini catalogue (WGACAT) of ROSAT-pspc pointed observations. Of 1744 X-ray sources, 1410 (80.9%) are new AGN identifications. Of 4,574 SDSS DR4 AGNs for which we found radio matches in the catalogue of radio sources from the Faint Images of the Radio Sky at Twenty (FIRST) cm survey, 224 turned up in our sample of SDSS X-ray AGN.

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Star formation in low-redshift cluster dwarf galaxies

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa697 ◽

2020 ◽

Vol 493 (4) ◽

pp. 5625-5635

Author(s):

Cody M Rude ◽

Madina R Sultanova ◽

Gihan L Ipita Kaduwa Gamage ◽

Wayne A Barkhouse ◽

Sandanuwan P Kalawila Vithanage

Keyword(s):

Star Formation ◽

Dwarf Galaxies ◽

Sloan Digital Sky Survey ◽

Galaxy Interactions ◽

Cluster Data ◽

Luminosity Functions ◽

Sky Survey ◽

Ram Pressure ◽

Low Mass ◽

Central Concentration

ABSTRACT Evolution of galaxies in dense environments can be affected by close encounters with neighbouring galaxies and interactions with the intracluster medium. Dwarf galaxies (dGs) are important as their low mass makes them more susceptible to these effects than giant systems. Combined luminosity functions (LFs) in the r and u band of 15 galaxy clusters were constructed using archival data from the Canada–France–Hawaii Telescope. LFs were measured as a function of clustercentric radius from stacked cluster data. Marginal evidence was found for an increase in the faint-end slope of the u-band LF relative to the r-band with increasing clustercentric radius. The dwarf-to-giant ratio (DGR) was found to increase toward the cluster outskirts, with the u-band DGR increasing faster with clustercentric radius compared to the r-band. The dG blue fraction was found to be ∼2 times larger than the giant galaxy blue fraction over all clustercentric distance (∼5σ level). The central concentration (C) was used as a proxy to distinguish nucleated versus non-nucleated dGs. The ratio of high-C to low-C dGs was found to be ∼2 times greater in the inner cluster region compared to the outskirts (2.8σ level). The faint-end slope of the r-band LF for the cluster outskirts (0.6 ≤ r/r200 < 1.0) is steeper than the Sloan Digital Sky Survey field LF, while the u-band LF is marginally steeper at the 2.5σ level. Decrease in the faint-end slope of the r- and u-band cluster LFs towards the cluster centre is consistent with quenching of star formation via ram pressure stripping and galaxy–galaxy interactions.

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WATCAT: a tale of wide-angle tailed radio galaxies

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935058 ◽

2019 ◽

Vol 626 ◽

pp. A8 ◽

Cited By ~ 5

Author(s):

V. Missaglia ◽

F. Massaro ◽

A. Capetti ◽

M. Paolillo ◽

R. P. Kraft ◽

...

Keyword(s):

Radio Galaxies ◽

Sloan Digital Sky Survey ◽

Host Galaxy ◽

Wide Angle ◽

Host Galaxies ◽

Very Large Array ◽

Sky Survey ◽

Black Hole Masses ◽

Extended Emission ◽

Radio Power

We present a catalog of 47 wide-angle tailed radio galaxies (WATs), the WATCAT, mainly built including a radio morphological classification; WATs were selected by combining observations from the National Radio Astronomy Observatory/Very Large Array Sky Survey (NVSS), the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST), and the Sloan Digital Sky Survey (SDSS). We included in the catalog only radio sources showing two-sided jets with two clear “warmspots” (i.e., jet knots as bright as 20% of the nucleus) lying on the opposite side of the radio core, and having classical extended emission resembling a plume beyond them. The catalog is limited to redshifts z ≤ 0.15, and lists only sources with radio emission extended beyond 30 kpc from the host galaxy. We found that host galaxies of WATCAT sources are all luminous (−20.5 ≳ Mr ≳ −23.7), red early-type galaxies with black hole masses in the range 108 ≲ MBH ≲ 109 M⊙. The spectroscopic classification indicates that they are all low-excitation galaxies (LEGs). Comparing WAT multifrequency properties with those of FR I and FR II radio galaxies at the same redshifts, we conclude that WATs show multifrequency properties remarkably similar to FR I radio galaxies, having radio power of typical FR IIs.

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