PREDICTED SIZES OF PRESSURE-SUPPORTED HI CLOUDS IN THE OUTSKIRTS OF THE VIRGO CLUSTER

Blakesley Burkhart,Abraham Loeb

doi:10.3847/2041-8205/824/1/l7

Blakesley Burkhart, Abraham Loeb

Open Access

https://doi.org/10.3847/2041-8205/824/1/l7

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Abstract

ABSTRACT Using data from the ALFALFA AGES Arecibo HI survey of galaxies and the Virgo cluster X-ray pressure profiles from XMM-Newton, we investigate the possibility that starless dark HI clumps, also known as “dark galaxies,” are supported by external pressure in the surrounding intercluster medium. We find that the starless HI clump masses, velocity dispersions, and positions allow these clumps to be in pressure equilibrium with the X-ray gas near the virial radius of the Virgo cluster. We predict the sizes of these clumps to range from 1 to 10 kpc, in agreement with the range of sizes found for spatially resolved HI starless clumps outside of Virgo. Based on the predicted HI surface density of the Virgo sources, as well as a sample of other similar resolved ALFALFA HI dark clumps with follow-up optical/radio observations, we predict that most of the HI dark clumps are on the cusp of forming stars. These HI sources therefore mark the transition between starless HI clouds and dwarf galaxies with stars.

Highlights

Galaxy clusters are the most massive virialized structures in the present-day universe, containing dark matter halos of 1015M⊙, thousands of galaxies, and hot diffuse gas
Using data from the Taylor et al (2012) ALFALFA Arecibo HI survey of galaxies and the Virgo cluster Xray pressure profile from XMM-Newton, we investigated the possibility that starless dark HI clumps, known as “dark galaxies”, could be held together by support from the surrounding hot X-ray emitting intercluster medium (ICM)
We predict the sizes of these sources assuming pressure equilibrium with the ICM and find they range from 1 kpc to 10 kpc

Summary

INTRODUCTION

Galaxy clusters are the most massive virialized structures in the present-day universe, containing dark matter halos of 1015M⊙, thousands of galaxies, and hot diffuse gas (see review by Bohringer & Werner 2010). Initial detections of dark galaxies later revealed that they either have a very small stellar component (i.e. have just begun star formation) or are tidally stripped HI streams An example of this latter possibility is the source known as VIRGOHI21 (Minchin et al 2007), a dark galaxy that is part of a much larger extended structure (Haynes et al 2007).

DATA AND SURVEYS

EXTERNAL PRESSURE SUPPORT IN VIRGO AND LOW STAR FORMATION RATES

Findings

DISCUSSION

CONCLUSION