Results
Take a look at our previous project from the Virgo cluster and how citizen science played a key role in our results!
https://www.zooniverse.org/projects/mike-dot-jones-dot-astro/blobs-and-blurs-extreme-galaxies-in-clusters/about/results
We are just getting started! We have not yet begun our analysis of LSST DP2 data, but we will keep you in the loop as we learn about blue blobs and diffuse galaxies. Below you can find results of our previous Blobs and Blurs project to give you a taste of what is to come:
Diffuse Galaxies in the Fornax Cluster
The Blobs and Blurs project previously used imaging from the Fornax Deep Survey (FDS) to search for diffuse galaxies in the Fornax galaxy cluster. In order for an object to be considered a diffuse galaxy candidate, we required that at least 4 volunteers marked the same object. Using this metric, you identified 1,138 diffuse galaxy candidates in the Fornax Cluster! These candidates are plotted below in a map of Fornax, with some being identified by over 20 volunteers!
The candidates that were identified by a higher number of citizen scientists are most likely to exist in current diffuse galaxy catalogs of Fornax. We’re most interested in catalogs that were generated with automated detection methods, since their completeness is limited by the faint, smudge-like appearance of these galaxies. Many of these candidates have been cataloged by such methods, but you found 55 diffuse galaxies that were not found by any automated search! Here are a few standout examples of these objects:
This one is quite faint so we've included the VST image as well:
Possible reasons why automated searches missed these objects include:
- The diffuse galaxy was either too bright or too faint for the algorithm
- A nearby bright object (such as a star) obscured the diffuse galaxy from the algorithm
Although these objects don’t appear in any automated catalogs of Fornax, nearly all of them have been cataloged already through some form of visual inspection (usually focused on a subregion of Fornax). However, you found 4 completely new diffuse galaxy candidates that don’t appear in any existing catalogs—automated or visual—which is very exciting! We've included them here below:
You can read all the details of the Blob and Blurs search for diffuse galaxies in Fornax in our published paper.
Blue Blobs in the Virgo Cluster
The Blobs and Blurs project also previously conducted a search for blue blobs in the Virgo galaxy cluster using imaging from the Next Generation Virgo cluster Survey (NGVS). Although the deepest available data at the time, NGVS was much shallower than Rubin/LSST imaging, hence why we are reviving this search effort.
At the outset of the previous search, only five blue blobs were known in total. Zooniverse volunteers helped to identify an additional 13 high confidence blue blob candidates, more than doubling the number of known examples. Below are NGVS (optical) and GALEX (UV) images of two of the newly discovered objects, BC17 and BC30.
Many of these new candidates were followed up with optical spectroscopy using the Hobby-Eberly Telescope (HET; McDonald Observatory, University of Texas) to look for emission lines associated with recent star formation. These observations provide two key additional pieces of information, which allows the candidates to be confirmed as bona fide blue blobs. First, is the radial velocity that they are moving away from us. This allows us to verify if candidates have the same velocity as other objects in the Virgo cluster, and rule out the chance that they might be a much larger star-forming galaxy far in the background. Second, the relative strengths of the emission lines detected in the spectra reveals the chemical composition of the gas that stars are forming from. Typically, low-mass galaxies have minimal amounts of elements heavier than hydrogen and helium, while large galaxies like our Milky Way have many times more. Bona fide blue blobs are far more rich in these heavier elements than their sizes would imply.
Remarkably, some of the blue blobs discovered by Zooniverse volunteers appear to the be the stellar counterparts of previously known, enormous "dark" gas clouds lurking in the Virgo cluster, some of which had been thought to be entirely "dark" (i.e., without any stars at all) since they were first discovered over a decade ago. With the discovery of their blue blob counterparts, one of these systems is now the most gas-rich stellar system known, with over 20,000 times more mass in gas than it has in stars.
You can read all the details of the prior Blobs and Blurs search for blue blobs in the Virgo cluster in our published paper.