AGC 226178 and NGVS 3543: Two Deceptive Dwarfs toward Virgo

M G K Jones ,Dennis Zaritsky,Elizabeth A K Adams,Elisa Toloba,Nelson Caldwell,Jay Strader,David J Sand,Martha P Haynes,Paul Bennet,Burçin Mutlu-Pakdil,John L Inoue,Ananthan Karunakaran,Denija Crnojević,Jackson Fuson,Kristine Spekkens,Puragra Guhathakurta,Ricardo R Muñoz,Anil Seth,L Magrini ,John Cannon ,M Bellazzini ,G Cresci ,G Battaglia ,G Beccari

doi:10.3847/2041-8213/ac51dc

Abstract

Abstract The two sources AGC 226178 and NGVS 3543, an extremely faint, clumpy, blue stellar system and a low surface brightness dwarf spheroidal, are adjacent systems in the direction of the Virgo cluster. Both have been studied in detail previously, with it being suggested that they are unrelated normal dwarf galaxies or that NGVS 3543 recently lost its gas through ram pressure stripping and AGC 226178 formed from this stripped gas. However, with Hubble Space Telescope Advanced Camera for Surveys imaging, we demonstrate that the stellar population of NGVS 3543 is inconsistent with being at the distance of the Virgo cluster and that it is likely a foreground object at approximately 10 Mpc, whereas the stellar population of AGC 226178 is consistent with it being a very young (10–100 Myr) object in the Virgo cluster. Through a reanalysis of the original ALFALFA H i detection, we show that AGC 226178 likely formed from gas stripped from the nearby dwarf galaxy VCC 2034, a hypothesis strengthened by the high metallicity measured with MUSE VLT observations. However, it is unclear whether ram pressure or a tidal interaction is responsible for stripping the gas. Object AGC 226178 is one of at least five similar objects now known toward Virgo. These objects are all young and unlikely to remain visible for over ∼500 Myr, suggesting that they are continually produced in the cluster.

Highlights

Blind surveys of neutral hydrogen (H I) in the local universe have revealed a plethora of extremely high mass-to-light ratio systems that have few or no stars (Saul et al 2012; Adams et al 2013; Cannon et al 2015)
The regions used to produce the color–magnitude diagram (CMD) of AGC 226178 were manually constructed after comparison of the Hubble Space Telescope (HST) images and Hα detections in Multi Unit Spectroscopic Explorer (MUSE) (Section 3.4)
A velocity width of 30 km s−1 was assumed for Next Generation Virgo cluster Survey (NGVS) 3543 and 100 km s−1 for VCC 2045 and 2048. a Estimated by Junais et al (2021), normalized to the relevant distance. b Estimated by summing regions A, B, C, E, and H from Junais et al (2021, Table 3). c From Junais et al (2021, Table 2). d the RGB (TRGB) measurement from Karachentsev et al (2014). e Globular cluster luminosity function measurement from Villegas et al (2010)

Summary

Introduction

Blind surveys of neutral hydrogen (H I) in the local universe have revealed a plethora of extremely high mass-to-light ratio systems that have few or no stars (Saul et al 2012; Adams et al 2013; Cannon et al 2015). Some may be genuine Local Group dwarfs, similar to Leo T (Irwin et al 2007) and Leo P (Giovanelli et al 2013), while others appear to be unusual objects in the direction of the Virgo cluster (Cannon et al 2015; Bellazzini et al 2015b; Sand et al 2015; Adams et al 2015). The actual stellar counterpart was essentially invisible given the depth of the

Results

Discussion

Conclusion