Probing the low surface brightness dwarf galaxy population of the virgo cluster

Abstract

We have used public data from the Next Generation Virgo Survey (NGVS) to investigate the dwarf galaxy population of the Virgo cluster beyond what has previously been discovered. We initially mask and smooth the data, and then use the object detection algorithm S extractor to make our initial dwarf galaxy selection. All candidates are then visually inspected to remove artefacts and duplicates. We derive S extractor parameters to best select low surface brightness galaxies using central surface brightness values of 22.5 µ g 0 26.0 µg and exponential scale lengths of 3.0 h 10.0 arc sec to identify 443 cluster dwarf galaxies -303 of which are new detections, with a surface density that decreases with radius from the cluster centre. We also apply our selection algorithm to 'background', non-cluster, fields and find zero detections. In combination, this leads us to believe that we have isolated a cluster dwarf galaxy population. The range of objects we are able to detect is limited because smaller scale sized galaxies are confused with the background, while larger galaxies are split into numerous smaller objects by the detection algorithm. Using data from previous surveys combined with our data, we find a faint end slope to the luminosity function of −1.35 ± 0.03, which does not significantly differ to what has previously been found for the Virgo cluster, but is a little steeper than the slope for field galaxies. There is no evidence for a faint end slope steep enough to correspond with galaxy formation models, unless those models invoke either strong feedback processes or use warm dark matter.

Measurements of Extragalactic Background Light From the Far Uv to the Far Ir From Deep Ground- And Space-Based Galaxy Counts

“…Both studies explored the low-surface-brightness universe and, while finding numerous new systems, these systems ultimately contribute only small amounts of additional light (<20%; Driver 1999). Studies of rich clusters have also been very successful at finding low-surface-brightness systems (e.g., Davies et al 2016;van Dokkum et al 2015), yet not in sufficient quantities to significantly affect the total luminosity density, e.g., the thousand new galaxies found in the Coma cluster by Koda et al (2015) collectively add up to just one extra * L galaxy. Two final arguments can be made for a minimal amount of missing light from low-surface-brightness galaxies based on the actual number-count and IGL data.…”

The physics of galactic spin

“…1c), thus creating the postulated large amounts of non-baryons. Possible effects of non-luminous baryons inside [18,19,32] and outside [38] spiral galaxies have been discussed, but the importance of shape was overlooked, as is evident in the RHS of (4), and in the lack of discussion of I for galaxies in Binney and Tremaine's tome [28].…”

The Gould Belt

“…An analysis of the earliest observations of neutral hydrogen at 21 cm showed that its distribution is related to the Gould belt [57,58].…”

“…The total mass of interstellar dust in the vicinity of the sun is about 1% of the overall mass of available hydrogen [57,58]. Dark dust clouds are a serious problem when estimating the photometric distances to stars or diffuse stellar clusters.…”

“…Original estimates of the mass of neutral hydrogen and dust were obtained by Davis [58] using their concentration as derived from an extensive program of observations of radio-frequency hydrogen lines. They obtained a preliminary estimate for the mass of all the stars in the different spectral classes belonging to the Gould belt.…”