Galaxy formation and evolution

Research group

Research theme

Sub department

About

Merger rates of intermediate-mass black hole binaries in nuclear star clusters

Astrophysical Journal American Astronomical Society 933:2 (2022) 170

Authors:

Giacomo Fragione, Abraham Loeb, Bence Kocsis, Frederic A Rasio

Abstract:

Repeated mergers of stellar-mass black holes in dense star clusters can produce intermediate-mass black holes (IMBHs). In particular, nuclear star clusters at the centers of galaxies have deep enough potential wells to retain most of the black hole (BH) merger products, in spite of the significant recoil kicks due to anisotropic emission of gravitational radiation. These events can be detected in gravitational waves, which represent an unprecedented opportunity to reveal IMBHs. In this paper, we analyze the statistical results of a wide range of numerical simulations, which encompass different cluster metallicities, initial BH seed masses, and initial BH spins, and we compute the merger rate of IMBH binaries. We find that merger rates are in the range 0.01–10 Gpc−3 yr−1 depending on IMBH masses. We also compute the number of multiband detections in ground-based and space-based observatories. Our model predicts that a few merger events per year should be detectable with LISA, DECIGO, Einstein Telescope (ET), and LIGO for IMBHs with masses ≲1000 M⊙, and a few tens of merger events per year with DECIGO, ET, and LIGO only.

More details from the publisher
Details from ORA
More details
More details

Impact of radiation feedback on the formation of globular cluster candidates during cloud-cloud collisions

(2022)

Authors:

Daniel Han, Taysun Kimm, Harley Katz, Julien Devriendt, Adrianne Slyz
More details from the publisher
Details from ArXiV

The challenges of identifying Population III stars in the early universe

(2022)

Authors:

Harley Katz, Taysun Kimm, Richard S Ellis, Julien Devriendt, Adrianne Slyz
More details from the publisher
Details from ArXiV

A compressed sensing faraday depth reconstruction framework for the MeerKAT MIGHTEE-POL Survey

Proceedings of the 3rd URSI Atlantic and Asia Pacific Radio Science Meeting (AT-AP-RASC 2022) IEEE (2022) 1-4

Authors:

M Carcamo, A Scaife, R Taylor, M Jarvis, M Bowles, S Sekhar, L Heino, J Stil

Abstract:

In this work we present a novel compute framework for reconstructing Faraday depth signals from noisy and incomplete spectro-polarimetric radio datasets. This framework is based on a compressed-sensing approach that addresses a number of outstanding issues in Faraday depth reconstruction in a systematic and scaleable manner. We apply this framework to early-release data from the MeerKAT MIGHTEE polarisation survey.
More details from the publisher
Details from ORA
More details

Down but not out: properties of the molecular gas in the stripped Virgo Cluster early-type galaxy NGC4526

The Astrophysical Journal, 933:1 (2022) 90-119

Authors:

Lisa M. Young, David S. Meier, Alison Crocker, Timothy A. Davis, and Selçuk Topal

Abstract:

We present Atacama Large Millimeter/submillimeter Array data on the 3 mm continuum emission, CO isotopologues (12CO, 13CO, and C18O), and high-density molecular tracers (HCN, HCO+, HNC, HNCO, CS, CN, and CH3OH) in NGC 4526. These data enable a detailed study of the physical properties of the molecular gas in a longtime resident of the Virgo Cluster; comparisons to more commonly studied spiral galaxies offer intriguing hints into the processing of molecular gas in the cluster environment. Many molecular line ratios in NGC 4526, along with our inferred abundances and CO/H2 conversion factors, are similar to those found in nearby spirals. One striking exception is the very low observed 12CO/13CO(1−0) line ratio, 3.4 ± 0.3, which is unusually low for spirals though not for Virgo Cluster early-type galaxies. We carry out radiative transfer modeling of the CO isotopologues with some archival (2−1) data, and we use Bayesian analysis with Markov Chain Monte Carlo techniques to infer the physical properties of the CO-emitting gas. We find surprisingly low [12CO/13CO] abundance ratios of 7.8 and 6.5 at radii of 0.4 kpc and 1 kpc. The emission from the high-density tracers HCN, HCO+, HNC, CS, and CN is also relatively bright, and CN is unusually optically thick in the inner parts of NGC 4526. These features hint that processing in the cluster environment may have removed much of the galaxy's relatively diffuse, optically thinner molecular gas along with its atomic gas. Angular momentum transfer to the surrounding intracluster medium may also have caused contraction of the disk, magnifying radial gradients such as we find in [13CO/C18O]. More detailed chemical evolution modeling would be interesting in order to explore whether the unusual [12CO/13CO] abundance ratio is entirely an environmental effect or whether it also reflects the relatively old stellar population in this early-type galaxy.
More details from the publisher
Full PDF text