Deep optical imaging of the dark galaxy candidate AGESVC1 282

Michal Bílek,Oliver Müller,Ana Vudragović,Rhys Taylor

doi:10.1051/0004-6361/202039174

Michal Bílek, Oliver Müller + Show 2 more

Open Access

https://doi.org/10.1051/0004-6361/202039174

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Journal: Astronomy & Astrophysics	Publication Date: Oct 1, 2020
Citations: 4	License type: CC BY 4.0

Affiliation: Czech Academy of Sciences

Abstract

The blind H Isurvey Arecibo Galaxy Environment Survey (AGES) detected several unresolved sources in the Virgo cluster, which do not have optical counterparts in the Sloan Digital Sky Survey. The origin of these dark clouds is unknown. They might be crucial objects since they could be the so-called dark galaxies, that is, the dark matter halos without stellar content that are expected from cosmological simulations. In order to reveal the nature of the dark clouds, we took a deep optical image of one them, AGESVC1 282, with the newly-commissioned 1.4 mMilankovićTelescope. After observing it for 10.4 h in theL-filter, the image reached a surface-brightness limit of about 29.1 mag arcsec−2inV. No optical counterpart was detected. We placed an upper limit on theV-band luminosity of the object of 1.1 × 107 L⊙, giving a stellar mass below 1.4 × 107 M⊙and a H I-to-stellar mass ratio above 3.1. By inspecting archival H Iobservations of the surrounding region, we found that none of the standard explanations for optically dark H Iclouds fits the available constraints on this object.

Highlights

There has been a rise of interest in the low surface brightness (LSB) universe
The dark cloud AGESVC1 282 is one of several Hi sources associated with the Virgo cluster without optical counterparts in public surveys
In order to further constrain the nature of these objects, we undertook very deep imaging of AGESVC1 282

Summary

Introduction

There has been a rise of interest in the low surface brightness (LSB) universe. These objects were first reported in Taylor et al (2012, 2013) as part of the Arecibo Galaxy Environment Survey (AGES). Their radial velocities (1000−2000 km s−1) and distribution on the sky suggest that they are members of the Virgo cluster (in the case of AGESVC1 282 in the B cloud, at a distance of 23 Mpc, Gavazzi et al 1999) Their Hi masses are ∼1−3 × 107 M , which is consistent with other tidal debris; their combination of isolation (> 100 kpc from the nearest galaxy) and high line widths (∼150 km s−1) make them more unusual.

Observations and data reduction

Discussion and conclusions