A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE)

Monthly Notices of the Royal Astronomical Society

2020

Ram-pressure stripping (RPS) is a well observed phenomenon of massive spiral galaxies passing through the hot intra-cluster medium (ICM) of galaxy clusters. For dwarf galaxies (DGs) within a cluster, the transformation from gaseous to gas-poor systems by RPS is not easily observed and must happen in the outskirts of clusters. In a few objects in close by galaxy clusters and the field, RPS has been observed. Since cluster early-type DGs also show a large variety of internal structures (unexpected central gas reservoirs, blue stellar cores, composite radial stellar profiles), we aim in this study to investigate how ram pressure (RP) affects the interstellar gas content and therefore the star-formation (SF) activity. Using a series of numerical simulations, we quantify the dependence of the stripped-off gas on the velocity of the infalling DGs and on the ambient ICM density. We demonstrated that SF can be either suppressed or triggered by RP depending on the ICM density and the DGs mass. Under some conditions, RP can compress the gas, so that it is unexpectedly retained in the central DG region and forms stars. When gas clouds are still bound against stripping but lifted from a thin disk and fall back, their new stars form an ellipsoidal (young) stellar population already with a larger velocity dispersion without the necessity of harassment. Most spectacularly, star clusters can form downstream in stripped-off massive gas clouds in the case of strong RP. We compare our results to observations.

Section: Star-forming Blobsmentioning

confidence: 95%

The effect of ram-pressure stripping on dwarf galaxies

Steyrleithner

Hensler

Monthly Notices of the Royal Astronomical Society

2020

“…1 The NB filter has a very flat transmissivity profile (T 92%). A detailed description of the observing strategy and of the data reduction procedure is given in Boselli et al (2018). At present, the survey is ∼ 36% complete, with the full depth (where the sensitivity is f (Hα) ∼ 4 × 10 −17 erg s −1 cm −2 for point sources (5 σ)) reached in the central ∼ 16 deg 2 around M87, and in four independent outer regions ∼ 1 deg 2 each mapped during pilot observations.…”

Section: Narrow-band Imaging Datamentioning

confidence: 99%

“…The Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE, Boselli et al 2018) is a new deep blind Hα narrow-band (NB) imaging survey of the Virgo cluster carried out at the CFHT with MegaCam. Designed to cover the whole Virgo cluster up to its virial radius (104 deg 2 ), this survey is perfectly suited to study the effects of the environment on the star formation process in perturbed galaxies down to scales of 100 pc.…”

Section: Introductionmentioning

confidence: 99%

A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE)

Fossati

Cuillandre

et al. 2018

A&A

Self Cite

The Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE) is a blind narrow-band Hα+ [NII] imaging survey of the Virgo cluster carried out with MegaCam at the Canada-French-Hawaii telescope (CFHT). We use a new set of data extracted from VESTIGE to study the impact of the hostile cluster environment on the star formation process down to the scale of HII regions (∼ 50 pc). HII regions are identified and their parameters measured using the HIIphot code on a sample of 114 late-type galaxies spanning a wide range in morphological type (Sa-Sd, Im, BCD), stellar mass (10 6.5 ≤ M star ≤ 10 11 M ), and star formation activity (10 −3 ≤ S FR ≤ 10 M yr −1 ). Owing to the exquisite average resolution of the VESTIGE data (0.65 arcsec), we detect 11302 HII regions with an Hα luminosity L(Hα) ≥ 10 37 erg s −1 . We show that the typical number of HII regions in gas-stripped objects is significantly lower than in healthy late-types of similar stellar mass. We also show that in these gas-stripped galaxies the number of HII regions significantly drops outside the effective radius, suggesting that the quenching process occurs outside-in, in agreement with other multifrequency observations. These new results consistently confirm that the main mechanism responsible for the decrease of the star formation activity observed in cluster galaxies is ram pressure, allowing us to discard other milder processes such as starvation or strangulation unable to reproduce the observed radially truncated profiles.

“…This undoubtedly states that the ionised gas tail formed after the interaction of the galaxy interstellar medium (ISM) with the ICM. The most striking examples have been found first in the nearby cluster A1367 by Gavazzi et al (2001) (see also Boselli & Gavazzi 2014;Gavazzi et al 2017;Consolandi et al 2017) and are now becoming common in other clusters such as Norma (Zhang et al 2013), Coma (Yagi et al 2007(Yagi et al , 2010Fossati et al 2012;Gavazzi et al 2018) and Virgo (Yoshida et al 2002;Kenney et al 2008;Boselli et al 2016aBoselli et al , 2018bFossati et al 2018). Tails of stripped material have been observed also in H i (Chung et al 2007;Scott et al 2012), in CO (Jáchym et al 2013(Jáchym et al , 2014(Jáchym et al , 2017, and in X-rays (Sun et al 2006(Sun et al , 2007(Sun et al , 2010, indicating that the other gas phases can also be perturbed during the interaction.…”

Section: Introductionmentioning

confidence: 97%

Evidence for ram-pressure stripping in a cluster of galaxies at z = 0.7

Épinat

Contini

et al. 2019

A&A

Self Cite

MUSE observations of the cluster of galaxies CGr32 (M 200 2 × 10 14 M ) at z = 0.73 reveal the presence of two massive star forming galaxies with extended tails of diffuse gas detected in the [O ii]λλ3727-3729Å emission-line doublet. The tails, which have a cometary shape with a typical surface brightness of a few 10 −18 erg s −1 cm −2 arcsec −2 , extend up to 100 kpc (projected distance) from the galaxy discs and are not associated to any stellar component. All this observational evidence suggests that the gas has been removed during a ram-pressure stripping event. This observation is thus the first evidence that dynamical interactions with the intracluster medium were active when the Universe had only half of its present age. The density of the gas derived using the observed [O ii]λ3729/[O ii]λ3726 line ratio implies a very short recombination time, suggesting that a source of ionisation is necessary to keep the gas ionised within the tail.