Understanding galaxy mergers and AGN feedback with UVIT

AbstractSimulations expect an enhanced star-formation and active galactic nuclei (AGN) activity during galaxy mergers, which can lead to formation of binary/dual AGN. AGN feedback can enhance or suppress star-formation. We have carried out a pilot study of a sample of ˜10 dual nuclei galaxies with AstroSat’s Ultraviolet Imaging Telescope (UVIT). Here, we present the initial results for two sample galaxies (Mrk 739, ESO 509) and deep multi-wavelength data of another galaxy (Mrk 212). UVIT observations have revealed signatures of positive AGN feedback in Mrk 739 and Mrk 212, and negative feedback in ESO 509. Deeper UVIT observations have recently been approved; these will provide better constraints on star-formation as well as AGN feedback in these systems.

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A Catalog of 204 Offset and Dual Active Galactic Nuclei (AGNs): Increased AGN Activation in Major Mergers and Separations under 4 kpc

The Astrophysical Journal ◽

10.3847/1538-4357/ac0bbf ◽

2021 ◽

Vol 923 (1) ◽

pp. 36

Author(s):

Aaron Stemo ◽

Julia M. Comerford ◽

R. Scott Barrows ◽

Daniel Stern ◽

Roberto J. Assef ◽

...

Keyword(s):

Star Formation ◽

Active Galactic Nuclei ◽

Hubble Space Telescope ◽

Formation Rate ◽

Galactic Nuclei ◽

Host Galaxy ◽

Galaxy Mergers ◽

Mass Ratio ◽

Merging Galaxies ◽

Pair Separation

Abstract During galaxy mergers, gas and dust are driven toward the centers of merging galaxies, triggering enhanced star formation and supermassive black hole (SMBH) growth. Theory predicts that this heightened activity peaks at SMBH separations <20 kpc; if sufficient material accretes onto one or both of the SMBHs for them to become observable as active galactic nuclei (AGNs) during this phase, they are known as offset and dual AGNs, respectively. To better study these systems, we have built the ACS-AGN Merger Catalog, a large catalog (N = 204) of uniformly selected offset and dual AGN observed by the Hubble Space Telescope at 0.2 < z < 2.5 with separations <20 kpc. Using this catalog, we answer many questions regarding SMBH−galaxy coevolution during mergers. First, we confirm predictions that the AGN fraction peaks at SMBH pair separations <10 kpc; specifically, we find that the fraction increases significantly at pair separations of <4 kpc. Second, we find that AGNs in mergers are preferentially found in major mergers and that the fraction of AGNs found in mergers follows a logarithmic relation, decreasing as merger mass ratio increases. Third, we do not find that mergers (nor the major or minor merger subpopulations) trigger the most luminous AGNs. Finally, we find that nuclear column density, AGN luminosity, and host galaxy star formation rate have no dependence on SMBH pair separation or merger mass ratio in these systems, nor do the distributions of these values differ significantly from that of the overall AGN population.

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Observational Constraints on Correlated Star Formation and Active Galactic Nuclei in Late-stage Galaxy Mergers

The Astrophysical Journal ◽

10.3847/1538-4357/aa93de ◽

2017 ◽

Vol 850 (1) ◽

pp. 27 ◽

Cited By ~ 9

Author(s):

R. Scott Barrows ◽

Julia M. Comerford ◽

Nadia L. Zakamska ◽

Michael C. Cooper

Keyword(s):

Star Formation ◽

Active Galactic Nuclei ◽

Late Stage ◽

Galactic Nuclei ◽

Observational Constraints ◽

Galaxy Mergers

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Peering into the heart of darkness: Radio VLBI survey of the NEP deep field

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320003385 ◽

2019 ◽

Vol 15 (S356) ◽

pp. 366-366

Author(s):

Joseph Gelfand

Keyword(s):

Active Galactic Nuclei ◽

Angular Resolution ◽

Galactic Nuclei ◽

Powerful Radio ◽

Host Galaxies ◽

Radio Jets ◽

Heart Of Darkness ◽

Multi Wavelength ◽

Initial Results ◽

Size Scales

AbstractActive Galactic Nuclei (AGN), accreting supermassive black holes at the centers of galaxies, are believed to produce powerful outflows – often observed as radio jets – which significantly influence the evolution of the surrounding galaxy and inter-galactic medium. However, how these jets – which are produced in the central parsecs of the AGN – impact gas on scales thousands to millions times larger is poorly understood. Doing so requires measuring the properties on all the relevant size scales. In this talk I will present initial results from the deepest-ever radio VLBI survey of an extragalactic field, whose milli-arcsecond angular resolution allows us to probe the central parsecs around these AGN. By comparing the radio properties of the detected radio jets with the multi-wavelength properties of their host galaxies, we are better to understand what galaxies generate powerful radio jets, and how do these outflows affect their host galaxies.

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Obtaining the (dust-obscured) star formation history using the VLA-COSMOS survey

Proceedings of the International Astronomical Union ◽

10.1017/s1743921306010556 ◽

2006 ◽

Vol 2 (S235) ◽

pp. 428-428

Author(s):

V. Smolčić ◽

E. Schinnerer ◽

M. Scodeggio ◽

C.L. Carilli ◽

P. Franzetti ◽

...

Keyword(s):

Star Formation ◽

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Photometric Data ◽

Star Formation History ◽

Star Forming ◽

Radio Data ◽

Formation History ◽

First Results ◽

Multi Wavelength

AbstractUsing the multi-wavelength COSMOS survey (Scoville et al. 2006), we develop a method based on purely photometric data to separate the faint VLA-COSMOS radio population into star-forming (SF) galaxies and active-galactic nuclei (AGN). Based on this classification method we select SF galaxies within our sample and present first results on the cosmic (dust-obscured) star-formation history based on VLA-COSMOS (Schinnerer et al. 2006) radio data.

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The ASKAP Variables and Slow Transients (VAST) Pilot Survey

Publications of the Astronomical Society of Australia ◽

10.1017/pasa.2021.44 ◽

2021 ◽

Vol 38 ◽

Author(s):

Tara Murphy ◽

David L. Kaplan ◽

Adam J. Stewart ◽

Andrew O’Brien ◽

Emil Lenc ◽

...

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Integration Time ◽

Central Frequency ◽

Pilot Survey ◽

Radio Detection ◽

Observation Strategy ◽

Transient Sources ◽

Multi Wavelength ◽

Initial Results

Abstract The Variables and Slow Transients Survey (VAST) on the Australian Square Kilometre Array Pathfinder (ASKAP) is designed to detect highly variable and transient radio sources on timescales from 5 s to $\sim\!5$ yr. In this paper, we present the survey description, observation strategy and initial results from the VAST Phase I Pilot Survey. This pilot survey consists of $\sim\!162$ h of observations conducted at a central frequency of 888 MHz between 2019 August and 2020 August, with a typical rms sensitivity of $0.24\ \mathrm{mJy\ beam}^{-1}$ and angular resolution of $12-20$ arcseconds. There are 113 fields, each of which was observed for 12 min integration time, with between 5 and 13 repeats, with cadences between 1 day and 8 months. The total area of the pilot survey footprint is 5 131 square degrees, covering six distinct regions of the sky. An initial search of two of these regions, totalling 1 646 square degrees, revealed 28 highly variable and/or transient sources. Seven of these are known pulsars, including the millisecond pulsar J2039–5617. Another seven are stars, four of which have no previously reported radio detection (SCR J0533–4257, LEHPM 2-783, UCAC3 89–412162 and 2MASS J22414436–6119311). Of the remaining 14 sources, two are active galactic nuclei, six are associated with galaxies and the other six have no multi-wavelength counterparts and are yet to be identified.

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Polarimetric Properties of Blazars Caught by the WEBT

Galaxies ◽

10.3390/galaxies9020042 ◽

2021 ◽

Vol 9 (2) ◽

pp. 42

Author(s):

Claudia M. Raiteri ◽

Massimo Villata

Keyword(s):

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Plasma Jets ◽

Line Of Sight ◽

Optical Behaviour ◽

Relativistic Jets ◽

Comprehensive Picture ◽

Multi Wavelength ◽

Extreme Variability ◽

Continuous Range

Active galactic nuclei come in many varieties. A minority of them are radio-loud, and exhibit two opposite prominent plasma jets extending from the proximity of the supermassive black hole up to megaparsec distances. When one of the relativistic jets is oriented closely to the line of sight, its emission is Doppler beamed and these objects show extreme variability properties at all wavelengths. These are called “blazars”. The unpredictable blazar variability, occurring on a continuous range of time-scales, from minutes to years, is most effectively investigated in a multi-wavelength context. Ground-based and space observations together contribute to give us a comprehensive picture of the blazar emission properties from the radio to the γ-ray band. Moreover, in recent years, a lot of effort has been devoted to the observation and analysis of the blazar polarimetric radio and optical behaviour, showing strong variability of both the polarisation degree and angle. The Whole Earth Blazar Telescope (WEBT) Collaboration, involving many tens of astronomers all around the globe, has been monitoring several blazars since 1997. The results of the corresponding data analysis have contributed to the understanding of the blazar phenomenon, particularly stressing the viability of a geometrical interpretation of the blazar variability. We review here the most significant polarimetric results achieved in the WEBT studies.

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Constraining photoionization models with a reprojected optical diagnostic diagram

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3259 ◽

2020 ◽

Vol 499 (4) ◽

pp. 5749-5764 ◽

Cited By ~ 1

Author(s):

Xihan Ji ◽

Renbin Yan

Keyword(s):

Star Formation ◽

Active Galactic Nuclei ◽

Galactic Nuclei ◽

Theoretical Models ◽

Line Ratio ◽

Star Forming ◽

Optical Diagnostic ◽

Diagnostic Diagram ◽

Upper Limits ◽

Nitrogen Abundance

ABSTRACT Optical diagnostic diagrams are powerful tools to separate different ionizing sources in galaxies. However, the model-constraining power of the most widely used diagrams is very limited and challenging to visualize. In addition, there have always been classification inconsistencies between diagrams based on different line ratios, and ambiguities between regions purely ionized by active galactic nuclei (AGNs) and composite regions. We present a simple reprojection of the 3D line ratio space composed of [N ii]λ6583/H α, [S ii]λλ6716, 6731/H α, and [O iii]λ5007/H β, which reveals its model-constraining power and removes the ambiguity for the true composite objects. It highlights the discrepancy between many theoretical models and the data loci. With this reprojection, we can put strong constraints on the photoionization models and the secondary nitrogen abundance prescription. We find that a single nitrogen prescription cannot fit both the star-forming locus and AGN locus simultaneously, with the latter requiring higher N/O ratios. The true composite regions stand separately from both models. We can compute the fractional AGN contributions for the composite regions, and define demarcations with specific upper limits on contamination from AGN or star formation. When the discrepancy about nitrogen prescriptions gets resolved in the future, it would also be possible to make robust metallicity measurements for composite regions and AGNs.

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Intensity ratios for XDR/PDR identification

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316007912 ◽

2015 ◽

Vol 11 (S315) ◽

Author(s):

C.-E. Green ◽

M. R. Cunningham ◽

J. A. Green ◽

J. R. Dawson ◽

P. A. Jones ◽

...

Keyword(s):

Black Holes ◽

Star Formation ◽

Active Galactic Nuclei ◽

Intensity Ratio ◽

Galactic Nuclei ◽

Relative Influence ◽

Calculation Methods ◽

X Ray ◽

Ratio Calculation ◽

Intensity Ratios

AbstractThe intensity ratios of HCO+/HCN and HNC/HCN (1-0) reveal the relative influence of star formation and active galactic nuclei (AGN) or black holes on the circum-nuclear gas of a galaxy, allowing the identification of X-ray dominated regions (XDRs) and Photon-dominated regions (PDRs). It is not always clear in the literature how this intensity ratio calculation has been, or should be performed. This paper discusses ratio calculation methods for interferometric data.

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