The MeerKAT Fornax Survey

We present the science case and observations plan of the MeerKAT Fornax Survey, an HI and radio continuum survey of the Fornax galaxy cluster to be carried out with the SKA precursor MeerKAT. Fornax is the second most massive cluster within 20 Mpc and the largest nearby cluster in the southern hemisphere. Its low X-ray luminosity makes it representative of the environment where most galaxies live and where substantial galaxy evolution takes place. Fornax's ongoing growth makes it an excellent laboratory for studying the assembly of clusters, the physics of gas accretion and stripping in galaxies falling in the cluster, and the connection between these processes and the neutral medium in the cosmic web. We will observe a region of 12 deg2 reaching a projected distance of 1.5 Mpc from the cluster centre. This will cover a wide range of environment density out to the outskirts of the cluster, where gas-rich in-falling groups are found. We will: study the HI morphology of resolved galaxies down to a column density of a few times 1e+19 cm−2 at a resolution of 1 kpc; measure the slope of the HI mass function down to M(HI) 5e+5 M(sun); and attempt to detect HI in the cosmic web reaching a column density of 1e+18 cm−2 at a resolution of 10 kpc

Metal enrichment processes

There are many processes that can transport gas from the galaxies to their environment and enrich the environment in this way with metals. These metal enrichment processes have a large influence on the evolution of both the galaxies and their environment. Various processes can contribute to the gas transfer: ram-pressure stripping, galactic winds, AGN outflows, galaxy-galaxy interactions and others. We review their observational evidence, corresponding simulations, their efficiencies, and their time scales as far as they are known to date. It seems that all processes can contribute to the enrichment. There is not a single process that always dominates the enrichment, because the efficiencies of the processes vary strongly with galaxy and environmental properties.Comment: 18 pages, 8 figures, accepted for publication in Space Science Reviews, special issue "Clusters of galaxies: beyond the thermal view", Editor J.S. Kaastra, Chapter 17; work done by an international team at the International Space Science Institute (ISSI), Bern, organised by J.S. Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke

GASP XXVI. HI gas in jellyfish galaxies : the case of JO201 and JO206

Please read abstract in the article.European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme grant agreement no. 679627 and no.833824, project name FORNAX and GASP, respectively. We acknowledge funding from the agreement ASI-INAF n.2017-14-H.0, as well as from the INAF main-stream funding programme. M. R’s research is supported by the SARAO HCD programme via the "New Scientific Frontiers with Precision Radio Interferometry" research group grant. M. R. acknowledges support from the Italian Ministry of Foreign A airs and International Cooperation (MAECI Grant Number ZA18GR02) and the South African Department of Science and Technology’s National Research Foundation (DST-NRF Grant Number 113121) as part of the ISARP RADIOSKY2020 Joint Research Scheme. B. V. and M. G. also acknowledge the Italian PRIN-Miur 2017 (PI A. Cimatti). Y. J. acknowledges financial support from CONICYT PAI (Concurso Nacional de Insercion en la Academia 2017), No. 79170132 and FONDECYT Iniciación 2018 No. 11180558. M. V. acknowledges support by the Netherlands Foundation for Scientific Research (NWO) through VICI grant 016.130.338.http://www.aanda.orgam2020Physic

The MeerKAT Fornax Survey. I. Survey description and first evidence of ram pressure in the Fornax galaxy cluster

The MeerKAT Fornax Survey maps the distribution and kinematics of atomic neutral hydrogen gas (HI) in the nearby Fornax galaxy cluster using the MeerKAT telescope. The 12 deg^2 survey footprint covers the central region of the cluster out to ~ Rvir and stretches out to ~ 2 Rvir towards south west to include the NGC 1316 galaxy group. The HI column density sensitivity (3 sigma over 25 km/s) ranges from 5e+19/cm^2 at a resolution of ~ 10" (~ 1 kpc at the 20 Mpc distance of Fornax) down to ~ 1e+18/cm^2 at ~ 1' (~ 6 kpc), and slightly below this level at the lowest resolution of ~ 100" (~ 10 kpc). The HI mass sensitivity (3 sigma over 50 km/s) is 6e+5 Msun. The HI velocity resolution is 1.4 km/s. In this paper we describe the survey design and HI data processing, and we present a sample of six galaxies with long, one-sided, star-less HI tails (of which only one was previously known) radially oriented within the cluster and with measurable internal velocity gradients. We argue that the joint properties of the HI tails represent the first unambiguous evidence of ram pressure shaping the distribution of HI in the Fornax cluster. The disturbed optical morphology of all host galaxies supports the idea that the tails consist of HI initially pulled out of the galaxies' stellar body by tidal forces. Ram pressure was then able to further displace the weakly bound HI and give the tails their present direction, length and velocity gradient.Comment: Astronomy & Astrophysics, accepted. Data available at the MeerKAT Fornax Survey website https://sites.google.com/inaf.it/meerkatfornaxsurve

Declining Rotation Curves: The End of a Conspiracy?

New observations of H I rotation curves at the Very Large Array have uncovered two galaxies with rotation curves declining between 1 and 3 optical radii. The velocity decrease is large, more than 50 km s-1 (approximately 25% of the maximum rotation velocity), and is present on both sides of the galaxies; projection effects can be ruled out. We interpret the decrease in rotation velocity as an indication of a large ratio of luminous to dark mass in the luminous regions of these systems. An analysis of the current observations combined with rotation curves from the literature shows a clear correlation between peak circular velocity of a galaxy, its central surface brightness and the slope of the rotation curve in the outer parts. This correlation indicates a weakening of the well-known conspiracy between luminous and dark matter, and may provide evidence in favor of the idea that dark matter is baryonic. Although we do not sample the full morphological Hubble sequence, a strong correlation between slope of the rotation curve and morphological type is found. This result seems to support earlier suggestions that the ratio between the mass in dark and luminous matter might be the critical parameter that controls the Hubble sequence

Aperture synthesis observations of recombination lines from compact HII regions

SIGLEBSE B210189W / UCL - Université Catholique de LouvainBEBelgiu

Kinematics and neutral hydrogen properties of the giant low surface brightness galaxy UGC 2936

We present high-sensitivity, high-velocity resolution VLA H I observations of the giant low surface brightness (LSB) galaxy, UGC 2936. Like the giant LSBs presented in Pickering et al., UGC 2936 is a large and massive galaxy. Its H I mass is nearly 10(10) M-circle dot h(75)(-2), it has detectable H I extending beyond 30 kpc h(75)(-1), and it is a fast rotator (V-max similar or equal to 250 km s(-1)) with a slowly rising rotation curve. This galaxy also exhibits warping in the outermost isophotes of the optical images that appears to be visible in the H I distribution and kinematics as well. This galaxy's high inclination and relatively large amount of Her emission provides a unique opportunity to compare high-quality H I and optical rotation curves in the same LSB galaxy. The optical and H I data show good agreement as long as the effects of beam smearing on the H I rotation curve are taken into account. A large part of the disk of UGC 2936 lies above the critical density for star formation as described by Kennicutt. This is consistent with the relatively large amount of star formation occurring within the disk of this galaxy and perhaps brings into question whether this galaxy should be considered a true LSB galaxy