What Powers Ultra-Luminous IRAS Galaxies?

I report here centimeter–wavelength observations carried out at the Very Large Array (VLA) to help resolve two questions. First, what is the source of the far infrared (FIR) emission in infrared-luminous IRAS galaxies, active nuclei or more widely distributed star formation? And what physics underlies the tight correlation (Helou et al., 1985) between FIR and radio flux? To test potential answers to these questions, we believe it is important to study the most luminous IRAS galaxies. We selected 39 for study from the ultraluminous catalog of Strauss et al.(1990 and 1992). All sources had FIR luminosity ≥ 1011.4 L⊙. Radio wavelength observations of these systems provide several advantages. First, in the radio there is no obscuration, so we can “see” the active galactic nuclei, if present. Radio spectral indices can distinguish between synchrotron and thermal emission. And finally, observations at the VLA provide sub–kpc resolution. We observed these sources with the VLA in its C configuration. At 1460 MHz, the effective resolution was ≃ 15″; and ≃ 4″ at 4860 MHz. We made follow-up observations on 24 sources in the A configuration with resolution at 4860 MHz of ≃ 0″.5 (or 300–800 h–1 pc for these sources).

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Variable radio AGN at high redshift identified in the VLA Sky Survey

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320001921 ◽

2020 ◽

Vol 15 (S359) ◽

pp. 27-32

Author(s):

Kristina Nyland ◽

Dillon Dong ◽

Pallavi Patil ◽

Mark Lacy ◽

Amy Kimball ◽

...

Keyword(s):

Active Galactic Nuclei ◽

High Redshift ◽

Galactic Nuclei ◽

Very Large Array ◽

The Past ◽

Sky Survey ◽

Upper Limits ◽

Radio Transients ◽

Variable Radio

AbstractAs part of an on-going study of radio transients in Epoch 1 (2017–2019) of the Very Large Array Sky Survey (VLASS), we have discovered a sample of 0.2 < z < 3.2 active galactic nuclei (AGN) selected in the optical/infrared that have recently brightened dramatically in the radio. These sources would have previously been classified as radio-quiet based on upper limits from the Faint Images of the Radio Sky at Twenty-centimeters (FIRST; 1993-2011) survey; however, they are now consistent with radio-loud quasars. We present a quasi-simultaneous, multi-band (1–18 GHz) VLA follow-up campaign of our sample of AGN with extreme radio variability. We conclude that the radio properties are most consistent with AGN that have recently launched jets within the past few decades, potentially making them among the youngest radio AGN known.

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Radio continuum properties of OH megamaser galaxies

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab3542 ◽

2021 ◽

Author(s):

Yu V Sotnikova ◽

Wu Zhongzu ◽

T V Mufakharov ◽

A G Mikhailov ◽

M G Mingaliev ◽

...

Keyword(s):

Active Galactic Nuclei ◽

Spectral Index ◽

Control Sample ◽

Galactic Nuclei ◽

Far Infrared ◽

Radio Continuum ◽

Ultraluminous Infrared Galaxy ◽

Two Samples ◽

Tight Correlation ◽

And Control

Abstract We present a study of the radio continuum properties of two luminous/ultraluminous infrared galaxy samples: the OH megamaser (OHM) sample (74 objects) and the control sample (128 objects) without detected maser emission. We carried out pilot observations for 140 objects with the radio telescope RATAN-600 at 1.2, 2.3, 4.7, 8.2, 11.2, and 22.3 GHz in 2019–2021. The OHM sample has two times more flat-spectrum sources (32 per cent) than the control sample. Steep radio spectra prevail in both samples. The median spectral index at 4.7 GHz α4.7 = −0.59 for the OHM sample, and α4.7 = −0.71 for the non-OHM galaxies. We confirm a tight correlation of the far-infrared (FIR) and radio luminosities for the OHM sample. We found correlations between isotropic OH line luminosity LOH and the spectral index α4.7 (ρ=0.26, p-val.=0.04) and between LOH and radio luminosity P1.4 (ρ=0.35, p-val.=0.005). Reviewing subsamples of masers powered by active galactic nuclei and star formation revealed insignificant differences for their FIR and radio properties. Nonetheless, AGN-powered galaxies exhibit larger scatter in a range of parameters and their standard deviations. The similarities in the radio and FIR properties in the two samples are presumably caused by the presence of a significant amount of AGN sources in both samples (47 and 30 per cent in the OHM and control samples) and/or possibly by the presence of undetected OH emission sources in the control sample.

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Multiwavelength analysis of OH Megamaser galaxies: The case of IRAS11506-3851

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320004317 ◽

2020 ◽

Vol 15 (S359) ◽

pp. 347-349

Author(s):

Carpes P. Hekatelyne ◽

Thaisa Storchi-Bergmann

Keyword(s):

Active Galactic Nuclei ◽

Hubble Space Telescope ◽

Galactic Nuclei ◽

Large Array ◽

Very Large Array ◽

Star Forming ◽

Star Forming Regions ◽

Field Unit ◽

Mixed Transition ◽

Integral Field

AbstractWe present Multi-Object Spectrograph (GMOS) Integral Field Unit (IFU), Hubble Space Telescope (HST) and Very Large Array (VLA) observations of the inner kpc of the OH Megamaser galaxy IRAS 11506-3851. In this work we discuss the kinematics and excitation of the gas as well as its radio emission. The HST images reveal an isolated spiral galaxy and the combination with the GMOS-IFU flux distributions allowed us to identify a partial ring of star-forming regions surrounding the nucleus with a radius of ≍500 pc. The emission-line ratios and excitation map reveal that the region inside the ring present mixed/transition excitation between those of Starbursts and Active Galactic Nuclei (AGN), while regions along the ring are excited by Starbursts. We suggest that we are probing a buried or fading AGN that could be both exciting the gas and originating an outflow.

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The Southern 2MASS Active Galactic Nuclei Survey: Spectroscopic Follow-up with Six Degree Field

Publications of the Astronomical Society of Australia ◽

10.1071/as10001 ◽

2010 ◽

Vol 27 (3) ◽

pp. 302-320 ◽

Cited By ~ 2

Author(s):

Frank J. Masci ◽

Roc M. Cutri ◽

Paul J. Francis ◽

Brant O. Nelson ◽

John P. Huchra ◽

...

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Far Infrared ◽

Type I ◽

Galactic Latitude ◽

Stellar Objects ◽

Identification Rate ◽

Near Ir ◽

The Uk ◽

Probable Type

AbstractThe Two Micron All-Sky Survey (2MASS) has provided a uniform photometric catalog to search for previously unknown red active galactic nuclei (AGN) and Quasi-Stellar Objects (QSOs).We have extended the search to the southern equatorial sky by obtaining spectra for 1182 AGN candidates using the six degree field (6dF) multifibre spectrograph on the UK Schmidt Telescope. These were scheduled as auxiliary targets for the 6dF Galaxy Redshift Survey. The candidates were selected using a single color cut of J – Ks > 2 to Ks ≲ 15.5 and a galactic latitude of lbl > 30°. 432 spectra were of sufficient quality to enable a reliable classification. 116 sources (∼27%) were securely classified as type I AGN, 20 as probable type I AGN, and 57 as probable type II AGN. Most of them span the redshift range 0.05 < z < 0.5 and only 8 (∼6%) were previously identified as AGN or QSOs. Our selection leads to a significantly higher AGN identification rate amongst local galaxies (>20%) than in any previous (mostly blue-selected) galaxy survey. A small fraction of the type I AGN could have their optical colors reddened by optically thin dust with AV < 2 mag relative to optically selected QSOs. A handful show evidence of excess far-infrared (IR) emission. The equivalent width (EW) and color distributions of the type I and II AGN are consistent with AGN unified models. In particular, the EW of the [Oiii] emission line weakly correlates with optical–near-IR color in each class of AGN, suggesting anisotropic obscuration of the AGN continuum. Overall, the optical properties of the 2MASS red AGN are not dramatically different from those of optically-selected QSOs. Our near-IR selection appears to detect the most near-IR luminous QSOs in the local universe to z≃0.6 and provides incentive to extend the search to deeper near-IR surveys.

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VLA Observations of a Sample of Low-Brightness 6.7 GHz Methanol Masers

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318000807 ◽

2017 ◽

Vol 13 (S336) ◽

pp. 311-312

Author(s):

Luca Olmi ◽

Esteban D. Araya ◽

Jason Armstrong

Keyword(s):

New Mexico ◽

Star Formation ◽

Far Infrared ◽

Large Array ◽

Very Large Array ◽

Early Stages ◽

Methanol Masers ◽

Infrared Sources ◽

Massive Cores

AbstractIn 2014 we conducted a survey for 6.7 GHz methanol masers with the Arecibo Telescope toward far infrared sources selected from the Hi-GAL catalog of massive cores. We found a number of sources with weak 6.7 GHz methanol masers, possibly indicating regions in early stages of star formation. Here we describe the results of follow-up observations that were conducted with the Very Large Array in New Mexico to characterize this new population of “weak” 6.7 GHz methanol masers.

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Localization of binary black hole mergers with known inclination

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2072 ◽

2019 ◽

Vol 488 (3) ◽

pp. 4459-4463 ◽

Cited By ~ 7

Author(s):

K Rainer Corley ◽

Imre Bartos ◽

Leo P Singer ◽

Andrew R Williamson ◽

Zoltán Haiman ◽

...

Keyword(s):

Black Hole ◽

Binary System ◽

Active Galactic Nuclei ◽

Prior Information ◽

Galactic Nuclei ◽

Electromagnetic Emission ◽

Accretion Discs ◽

Host Galaxies ◽

Binary Black Hole

ABSTRACT The localization of stellar-mass binary black hole mergers using gravitational waves is critical in understanding the properties of the binaries’ host galaxies, observing possible electromagnetic emission from the mergers, or using them as a cosmological distance ladder. The precision of this localization can be substantially increased with prior astrophysical information about the binary system. In particular, constraining the inclination of the binary can reduce the distance uncertainty of the source. Here, we present the first realistic set of localizations for binary black hole mergers, including different prior constraints on the binaries’ inclinations. We find that prior information on the inclination can reduce the localization volume by a factor of 3. We discuss two astrophysical scenarios of interest: (i) follow-up searches for beamed electromagnetic/neutrino counterparts and (ii) mergers in the accretion discs of active galactic nuclei.

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Monitoring the Extragalactic High Energy Sky

Galaxies ◽

10.3390/galaxies7010009 ◽

2019 ◽

Vol 7 (1) ◽

pp. 9 ◽

Cited By ~ 2

Author(s):

Jean-Philippe Lenain

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

High Energy ◽

Line Of Sight ◽

Data Sets ◽

High Energies ◽

Multi Wavelength ◽

Rich Data ◽

Very High

Blazars are jetted active galactic nuclei with a jet pointing close to the line of sight, hence enhancing their intrinsic luminosity and variability. Monitoring these sources is essential in order to catch them flaring and promptly organize follow-up multi-wavelength observations, which are key to providing rich data sets used to derive e.g., the emission mechanisms at work, and the size and location of the flaring zone. In this context, the Fermi-LAT has proven to be an invaluable instrument, whose data are used to trigger many follow-up observations at high and very high energies. A few examples are illustrated here, as well as a description of different data products and pipelines, with a focus given on FLaapLUC, a tool in use within the H.E.S.S. collaboration.

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AGN Feedback and its Importance to Galaxy Evolution in the Era of the ngVLA

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319003508 ◽

2018 ◽

Vol 14 (A30) ◽

pp. 78-81

Author(s):

Kristina Nyland

Keyword(s):

Star Formation ◽

Active Galactic Nuclei ◽

Galaxy Evolution ◽

Angular Resolution ◽

Galactic Nuclei ◽

Gas Content ◽

Large Array ◽

Very Large Array ◽

Frequency Coverage ◽

Evolutionary Role

AbstractEnergetic feedback by Active Galactic Nuclei (AGN) plays an important evolutionary role in the regulation of star formation (SF) on galactic scales. However, the effects of this feedback as a function of redshift and galaxy properties such as mass, environment and cold gas content remain poorly understood. The broad frequency coverage (1 to 116 GHz), high collecting area (about ten times higher than the Karl G. Jansky Very Large Array), and superb angular resolution (maximum baselines of at least a few hundred km) of the proposed next-generation Very Large Array (ngVLA) are uniquely poised to revolutionize our understanding of AGN and their role in galaxy evolution.

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AKARI Infrared Views of AGNs

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310005909 ◽

2009 ◽

Vol 5 (S267) ◽

pp. 129-129

Author(s):

Shinki Oyabu

Keyword(s):

Infrared Spectroscopy ◽

Active Galactic Nuclei ◽

Near Infrared Spectroscopy ◽

Near Infrared ◽

Galactic Nuclei ◽

Far Infrared ◽

Sky Survey

AbstractThe Japanese infrared satellite AKARI has unique capabilities for near-infrared spectroscopy and an all-sky survey in the mid- and far-infrared. We present the recent results on active galactic nuclei that use the unique capabilities of AKARI.

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