Young, Blue, and Isolated Stellar Systems in the Virgo Cluster. I. 2D Optical Spectroscopy

Abstract

We use panoramic optical spectroscopy obtained with the Very Large Telescope/MUSE to investigate the nature of five candidate extremely isolated low-mass star-forming regions (Blue Candidates; hereafter, BCs) toward the Virgo cluster of galaxies. Four of the five (BC1, BC3, BC4, and BC5) are found to host several H ii regions and to have radial velocities fully compatible with being part of the Virgo cluster. All the confirmed candidates have mean metallicity significantly in excess of that expected from their stellar mass, indicating that they originated from gas stripped from larger galaxies. In summary, these four candidates share the properties of the prototype system SECCO 1, suggesting the possible emergence of a new class of stellar systems, intimately linked to the complex duty cycle of gas within clusters of galaxies. A thorough discussion of the nature and evolution of these objects is presented in a companion paper, where the results obtained here from the MUSE data are complemented with Hubble Space Telescope (optical) and Very Large Array (Hi) observations.

Dark No More: The Low-luminosity Stellar Counterpart of a Dark Cloud in the Virgo Cluster*

“…Sand et al (2015) searched for other objects with similar optical and UV morphology to SECCO 1, identifying five additional candidates in Virgo. With Hubble Space Telescope (HST) imaging, plus Jansky Very Large Array (VLA), GBT, and Multi Unit Spectroscopic Explorer observations (Jones et al 2022a(Jones et al , 2022bBellazzini et al 2022), we demonstrated that four 11 of these are analogous to SECCO 1 (though not all are H I-rich) and argued that they represent a new class of object, which we will refer to simply as "blue blobs." The only viable mechanism to explain both the isolation and young ages of blue blobs is high-speed ram pressure stripping of H Ibearing galaxies falling into the cluster (Jones et al 2022b).…”

“…Beccari et al (2017) andBellazzini et al (2022) measured the metallicities of five blue blobs (SECCO 1, BC1, and BC3-5) using the same line ratio metrics as used here (see Section 3.5) and found a range of <…”