Triangle of ufd's and a dwarf elliptical

https://www.legacysurvey.org//viewer/?ra=191.9428&dec=9.1906&layer=ls-dr10&zoom=13

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When I was involved with Galaxy I & II, dim/faint amorphous blob galaxies like these (but not the elliptical) were called LSBs

Is LSB still used? If so there must be a great deal of correspondence between the two sets

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ultra-diffuse galaxies, perhaps, like dragonfly 44…I associate the term lsb’s with spirals, especially Sc types, M33 for example

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An LSB is a Low Surface Brightness galaxy. It is the term for any diffuse galaxy with a low brightness (I believe to technically be classified as an LSB it has to be one magnitude lower than the night sky). I don’t think there is any requirement on what type of galaxy is has to be but spirals are obviously more likely to have a low surface brightness. A UDG (ultra diffuse galaxy) is just an extreme case of this and is much less bright, sometimes even hard to see on a survey. This is because they have less star-forming gas (I think the consensus is that the gas has been ram-pressure stripped or used up but I’m not up to date on this so would love a second opinion) and so they are filled with OAP stars that are less luminous.

In this case, it would seem to me that the two on the left are definitely UDGs and there on the bottom right is likely a UDG but less definitely.

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++ Niko, you are right on all points.

In 2015 van Dokkum. using data from Dragonfly, named UDGs as a subset of LSBs in this letter:

FORTY-SEVEN MILKY WAY-SIZED, EXTREMELY DIFFUSE GALAXIES IN THE COMA CLUSTER

van Dokkum P. G. et al, 2015a, ApJ, 798, L45
10.1088/2041-8205/798/2/L45
https://iopscience.iop.org/article/10.1088/2041-8205/798/2/L45

This may be of interest:

The Fornax Deep Survey (FDS) with the VST: III. Low Surface Brightness (LSB) dwarfs and Ultra Diffuse Galaxies (UDGs) in the center of the Fornax cluster

A. Venhola et al, arXiv:1710.04616v2 [1710.04616v2] The Fornax Deep Survey (FDS) with the VST: III. Low Surface Brightness (LSB) dwarfs and Ultra Diffuse Galaxies (UDGs) in the center of the Fornax cluster)
[1710.04616] The Fornax Deep Survey (FDS) with the VST: III. Low Surface Brightness (LSB) dwarfs and Ultra Diffuse Galaxies (UDGs) in the center of the Fornax cluster

This June 2023 paper, José A Benavides et al support tidal effect formation of some UDGs

Origin and evolution of ultradiffuse galaxies in different environments

Monthly Notices of the Royal Astronomical Society, Volume 522, Issue 1, June 2023, Pages 1033–1048, https://doi.org/10.1093/mnras/stad1053
Origin and evolution of ultradiffuse galaxies in different environments | Monthly Notices of the Royal Astronomical Society | Oxford Academic

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Ah - thank you for all the papers. Sunday afternoon was looking a little empty and that “origin and evolution” paper looks interesting :slight_smile:

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You are welcome to check out my Dim Loners Collection at Galaxy Zoo
I’ve been told by one of the project astronomers that we can’t see LSBs at the distance we work at in the H2O Cosmic Dawn Survey we are working with.

I have seen many LSB-like objects while doing my 6.5k H2O classifications, so I decided to collect them.

I have recently come to believe that the custom filters used by H2O Cosmic Dawn to optimize HSC for faint objects may be more capable than she thought and that my DLGs are, in fact, LSBs.

If you click on the image you’ll get its page where you’ll see an “I” (information) icon below and to the right of the image. It contains metrics, links to NED - Simbad - Vizier, etc. including a photo-Z (which is pretty useless)

It is easy to trace the development of the galaxies - from blob to spiral or ellipitical - in the 333 examples

Have fun!

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