UVIT observations of the star-forming ring in NGC 7252: Evidence of possible AGN feedback suppressing central star formation

Context. Some post-merger galaxies are known to undergo a starburst phase that quickly depletes the gas reservoir and turns it into a red-sequence galaxy, though the details are still unclear. Aims. Here we explore the pattern of recent star formation in the central region of the post-merger galaxy NGC 7252 using high-resolution ultraviolet (UV) images from the UVIT on ASTROSAT. Methods. The UVIT images with 1.2 and 1.4 arcsec resolution in the FUV and NUV are used to construct a FUV-NUV colour map of the central region. Results. The FUV-NUV pixel colour map for this canonical post-merger galaxy reveals a blue circumnuclear ring of diameter ~10′′ (3.2 kpc) with bluer patches located over the ring. Based on a comparison to single stellar population models, we show that the ring is comprised of stellar populations with ages ≲300 Myr, with embedded star-forming clumps of younger age (≲150Myr). Conclusions. The suppressed star formation in the central region, along with the recent finding of a large amount of ionised gas, leads us to speculate that this ring may be connected to past feedback from a central super-massive black hole that has ionised the hydrogen gas in the central ~4′′ ~1.3 kpc.

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The relationship between black hole mass and galaxy properties: examining the black hole feedback model in IllustrisTNG

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa374 ◽

2020 ◽

Vol 493 (2) ◽

pp. 1888-1906 ◽

Cited By ~ 23

Author(s):

Bryan A Terrazas ◽

Eric F Bell ◽

Annalisa Pillepich ◽

Dylan Nelson ◽

Rachel S Somerville ◽

...

Keyword(s):

Black Hole ◽

Star Formation ◽

Galaxy Formation ◽

Formation Rate ◽

Black Hole Mass ◽

Star Forming ◽

Stellar Radius ◽

Accretion Rates ◽

Hole Model ◽

Galaxy Population

ABSTRACT Supermassive black hole feedback is thought to be responsible for the lack of star formation, or quiescence, in a significant fraction of galaxies. We explore how observable correlations between the specific star formation rate (sSFR), stellar mass (Mstar), and black hole mass (MBH) are sensitive to the physics of black hole feedback in a galaxy formation model. We use the IllustrisTNG simulation suite, specifically the TNG100 simulation and 10 model variations that alter the parameters of the black hole model. Focusing on central galaxies at z = 0 with Mstar > 1010 M⊙, we find that the sSFR of galaxies in IllustrisTNG decreases once the energy from black hole kinetic winds at low accretion rates becomes larger than the gravitational binding energy of gas within the galaxy stellar radius. This occurs at a particular MBH threshold above which galaxies are found to sharply transition from being mostly star forming to mostly quiescent. As a result of this behaviour, the fraction of quiescent galaxies as a function of Mstar is sensitive to both the normalization of the MBH–Mstar relation and the MBH threshold for quiescence in IllustrisTNG. Finally, we compare these model results to observations of 91 central galaxies with dynamical MBH measurements with the caveat that this sample is not representative of the whole galaxy population. While IllustrisTNG reproduces the observed trend that quiescent galaxies host more massive black holes, the observations exhibit a broader scatter in MBH at a given Mstar and show a smoother decline in sSFR with MBH.

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Twins born in different environments? Nuclei of two dSphs: isolated galaxy KKS3 and E269-66, a close neighbor of NGC5128

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316008693 ◽

2015 ◽

Vol 12 (S316) ◽

pp. 349-350

Author(s):

Margarita Sharina ◽

Alexei Kniazev ◽

Igor Karachentsev

Keyword(s):

Globular Clusters ◽

Massive Star ◽

Stellar Population ◽

Central Star ◽

Close Neighbor ◽

Dwarf Spheroidal Galaxies ◽

Star Forming ◽

Star Formation Histories ◽

Massive Clusters ◽

Centaurus A

AbstractWe present the results of age, metallicity and radial velocity determination for central massive globular clusters (GCs) in dwarf spheroidal galaxies: KKs3 and ESO269-66. KKS3 is a unique isolated galaxy. ESO269-66 is a close neighbor of the giant S0 Centaurus A. The results contribute to the knowledge about the origin of massive star clusters and their host dSphs. The structure and star formation histories of the two dwarf galaxies look rather similar. Both of them have experienced several star-forming events. The most recent ones occurred 1-2 Gyr ago, and most powerful bursts happened 12-14 Gyrs ago. Our analysis has shown that both GCs appear to be 1-2 Gyr younger and 0.1-0.3 dex more metal-rich than the most ancient metal-poor stars in the host dSphs. We examine signatures of multiple stellar population in the GCs using our data. Since central star-forming bursts were extended in time, the massive clusters might be considered as nuclei of the galaxies.

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The nearby extreme accretion and feedback system PDS 456: finding a complex radio-emitting nucleus

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2445 ◽

2020 ◽

Vol 500 (2) ◽

pp. 2620-2626

Author(s):

Jun Yang ◽

Zsolt Paragi ◽

Emanuele Nardini ◽

Willem A Baan ◽

Lulu Fan ◽

...

Keyword(s):

Black Hole ◽

Radio Emission ◽

High Speed ◽

Feedback System ◽

Emission Region ◽

Starburst Galaxy ◽

Massive Black Hole ◽

Star Forming ◽

Thermal Radio ◽

Thermal Radio Emission

ABSTRACT When a black hole accretes close to the Eddington limit, the astrophysical jet is often accompanied by radiatively driven, wide-aperture and mildly relativistic winds. Powerful winds can produce significant non-thermal radio emission via shocks. Among the nearby critical accretion quasars, PDS 456 has a very massive black hole (about 1 billion solar masses), shows a significant star-forming activity (about 70 solar masses per year), and hosts exceptionally energetic X-ray winds (power up to 20 per cent of the Eddington luminosity). To probe the radio activity in this extreme accretion and feedback system, we performed very long baseline interferometric (VLBI) observations of PDS 456 at 1.66 GHz with the European VLBI Network and the enhanced Multi-Element Remotely Linked Interferometry Network. We find a rarely seen complex radio-emitting nucleus consisting of a collimated jet and an extended non-thermal radio emission region. The diffuse emission region has a size of about 360 pc and a radio luminosity about three times higher than that of the nearby extreme starburst galaxy Arp 220. The powerful nuclear radio activity could result either from a relic jet with a peculiar geometry (nearly along the line of sight) or more likely from diffuse shocks formed naturally by the existing high-speed winds impacting on high-density star-forming regions.

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The AGN-galaxy connection: Low-redshift benchmark & lessons learnt

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319009517 ◽

2019 ◽

Vol 15 (S352) ◽

pp. 144-156

Author(s):

Stéphanie Juneau

Keyword(s):

Black Hole ◽

Star Formation ◽

Spatial Scales ◽

Formation Rate ◽

Cosmic Time ◽

Individual Case ◽

Host Galaxy ◽

Gas Reservoir ◽

Lessons Learnt

AbstractSeveral scenarios have been proposed to describe the physical connection between galaxies and their central active galactic nuclei (AGN). This connection could act on a range of spatial scales and vary across cosmic time. In these proceedings, we consider black hole and galaxy growth and whether that growth is affected by AGN feedback both based on statistical approaches – which reveal general population trends – and based on an individual case study – which gives us a more detailed insight on the physical processes at play. For the statistical approach, we showcase a low-redshift (0.04 < z < 0.2) SDSS sample with AGN classification based on a combination of emission-line diagnostic diagrams, and for which we account for sample selection by using a V/Vmax approach. The trends on the star formation rate - stellar mass (SFR – M*) plane suggest that the most likely connection is a common gas reservoir for star formation and AGN, and that they both decline as the gas reservoir is consumed. The trends established at low-redshift could act as a local benchmark against which to compare higher redshift studies. As a complementary approach, we use a detailed case study of a nearby AGN host with integral field spectroscopy from the VLT/MUSE instrument in order to spatially resolve the interplay between AGN feedback and the host galaxy. We find that the galaxy substructure likely plays a role by collimating and/or obscuring the outflows and radiation from the central engine. Ongoing and future work with 3D spectroscopy will enable us to learn more about galaxy and black hole coevolution. Lastly, we briefly discuss lessons learnt from both approaches.

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Tracing black hole and galaxy co-evolution in the Romulus simulations

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2161 ◽

2019 ◽

Vol 489 (1) ◽

pp. 802-819 ◽

Cited By ~ 7

Author(s):

Angelo Ricarte ◽

Michael Tremmel ◽

Priyamvada Natarajan ◽

Thomas Quinn

Keyword(s):

Black Hole ◽

Star Formation ◽

Star Formation Rate ◽

Accretion Rate ◽

Formation Rate ◽

Star Forming ◽

Black Hole Accretion ◽

Black Hole Growth ◽

Hole Growth ◽

Hole Accretion

ABSTRACT We study the link between supermassive black hole growth and the stellar mass assembly of their host galaxies in the state-of-the-art Romulus suite of simulations. The cosmological simulations Romulus25 and RomulusC employ innovative recipes for the seeding, accretion, and dynamics of black holes in the field and cluster environments, respectively. We find that the black hole accretion rate traces the star formation rate among star-forming galaxies. This result holds for stellar masses between 108 and 1012 solar masses, with a very weak dependence on host halo mass or redshift. The inferred relation between accretion rate and star formation rate does not appear to depend on environment, as no difference is seen in the cluster/proto-cluster volume compared to the field. A model including the star formation rate, the black hole-to-stellar mass ratio, and the cold gas fraction can explain about 70 per cent of all variations in the black hole accretion rate among star-forming galaxies. Finally, bearing in mind the limited volume and resolution of these cosmological simulations, we find no evidence for a connection between black hole growth and galaxy mergers, on any time-scale and at any redshift. Black holes and their galaxies assemble in tandem in these simulations, regardless of the larger scale intergalactic environment, suggesting that black hole growth simply follows star formation on galactic scales.

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The SFR Efficiency of HI Gas in the Outskirts of Star Forming Galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316009236 ◽

2016 ◽

Vol 11 (S321) ◽

pp. 360-362

Author(s):

Marc Rafelski

Keyword(s):

Star Formation ◽

Atomic Hydrogen ◽

Rest Frame ◽

Star Formation Rate ◽

Formation Rate ◽

Hydrogen Gas ◽

Star Forming ◽

Uv Emission ◽

Atomic Gas

AbstractIn order to understand the origin of the decreased star formation rate (SFR) efficiency of neutral atomic hydrogen gas measured in Damped Lyα Systems (DLAs) at z ~ 3, we measure the SFR efficiency of atomic gas at z ~ 1, z ~ 2, and z ~ 3 around star-forming galaxies. We create galaxy stacks in these three redshift bins, and measure the SFR efficiency by combining DLA absorber statistics with the observed rest-frame UV emission in the galaxies’ outskirts. We find that the SFR efficiency of Hi gas is ~ 3% of that predicted by the KS relation. We find no significant evolution in the SFR efficiency with redshift, although simulations and models predict a decreasing SFR efficiency with decreasing metallicity and thus with increasing redshift. We discuss possible explanations for this decreased efficiency without an evolution with redshift.

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OB stars towards NGC 6357 and NGC 6334

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317005385 ◽

2017 ◽

Vol 12 (S330) ◽

pp. 341-342

Author(s):

Delphine Russeil

Keyword(s):

Star Formation ◽

Massive Star ◽

Stellar Population ◽

Proper Motions ◽

Massive Star Formation ◽

Ob Stars ◽

Stellar Cluster ◽

Star Forming ◽

Star Forming Regions ◽

Ngc 6334

AbstractThe star forming regions NGC6334 and NGC6357 are amid the most active star-forming complexes of our Galaxy where massive star formation is occuring. Both complexes gather several HII regions but they exhibit different aspects: NGC6334 is characterised by a dense molecular ridge where recent massive star formation is obvious while NGC6357 is dominated by the action of the stellar cluster Pismis 24 which have shaped a large cavity. To understand and compare the formation of massive stars in these two regions requires to precise the distance and characterise the proper motions of the O to B3 stellar population in these regions.

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A New HI Ring: LGG 138

Publications of the Astronomical Society of Australia ◽

10.1071/as99077 ◽

1999 ◽

Vol 16 (1) ◽

pp. 77-83 ◽

Cited By ~ 7

Author(s):

David G. Barnes

Keyword(s):

Star Formation ◽

Stellar Population ◽

Density Wave ◽

Radial Distance ◽

Neutral Hydrogen ◽

Hydrogen Gas ◽

Radial Velocities ◽

Complete Ring ◽

Distinct Colour ◽

Colour Break

AbstractA complete ring of neutral hydrogen gas (HI) in the LGG 138 group of galaxies has been found. The HI mass of the ring is greater than 109, and the gas appears to be rotating with a projected circular speed of ∼200 km s−1. Two bright galaxies are enclosed by the ring, both having radial velocities consistent with membership of the group. Faint stellar emission extends to the radial distance of the HI ring, where a small but distinct colour discontinuity of between 0·05 and 0·20 magnitudes is detected. Three simple models for the formation of the system are briefly described, the most likely appearing to be a past gas-sweeping collision between one of the two bright galaxies and an outside intruder, with the colour break being partly due to an expanding density wave that is triggering star formation, and partly to a different stellar population that has been collected from the outskirts of the intruder.

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