| NSF Org: |
AST Division Of Astronomical Sciences |
| Recipient: |
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| Initial Amendment Date: | June 13, 2018 |
| Latest Amendment Date: | June 13, 2018 |
| Award Number: | 1812847 |
| Award Instrument: | Standard Grant |
| Program Manager: |
ANDREAS BERLIND
aberlind@nsf.gov (703)292-5387 AST Division Of Astronomical Sciences MPS Directorate for Mathematical and Physical Sciences |
| Start Date: | June 15, 2018 |
| End Date: | May 31, 2023 (Estimated) |
| Total Intended Award Amount: | $486,967.00 |
| Total Awarded Amount to Date: | $486,967.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
W5510 FRANKS MELVILLE MEMORIAL LIBRARY STONY BROOK NY US 11794-0001 (631)632-9949 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
NY US 11794-3800 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | EXTRAGALACTIC ASTRON & COSMOLO |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.049 |
ABSTRACT
Ultra-diffuse galaxies (UDGs) are a newly discovered population of galaxies. They are extremely faint, but spatially very extended, and are almost blended in the brightness of the night sky. Such diffuse galaxies are fragile, and cannot survive in gravitational encounters with other galaxies. However, astronomers are finding a great number of UDGs in clusters of galaxies, where such encounters would occur. This research program will investigate the nature and origin of these UDGs. It will study (1) whether UDGs are distinct from other types of galaxies such as the Milky Way and dwarf galaxies; (2) how they are protected from the gravitational disruptions; and (3) whether they have even fainter outskirts. The effects of gravitational encounters should appear clearly in the outskirts. This project will engage a variety of students in the research.
This program will use deep and wide-field imaging of eight local clusters of galaxies. The data are taken with the Hyper Suprime-Cam (HSC) on the Subaru telescope. These unique data will show the very faint outskirts of UDGs, as well as their large-scale environments. The program will perform the most reliable census and resolved analysis of the UDG population within, outside, and among the clusters. The main goals are (1) to confirm whether UDGs are distinct from dwarf and normal galaxies in their properties parameter spaces; (2) to constrain how they formed and how they their properties depend on their environments; and (3) to image their fainter outskirts and to discover even fainter, more extended UDGs. The project focuses primarily on UDGs, but aims to yield a broader, coherent picture that connects UDGs, dwarfs, and normal galaxies. UDGs are faint and extended, and are difficult to be detected and analyzed. The observations and data reduction will be optimized to achieve these goals.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Ultra diffuse galaxies (UDGs) are a mysterious galaxy population. They share a size comparable to that of the Milky Way (MW) galaxy, yet possess stellar masses in the range of only approximately 1/100 to 1/1000 that of the MW. Such extended and diffuse stellar structures should be susceptible to tidal disruptions by surrounding objects, especially within the strong gravitational environment of galaxy clusters. However, they are surprisingly abundant within galaxy clusters. Their red colors suggest that their stellar populations are old, and hence, they are surviving for a long time. Their longevity may require a very large fraction of dark matter whose gravitational pull protects the stellar structures from the strong tidal forces. The UDGs may present valuable examples to pin down crucial baryonic physics within dark matter during galaxy formation. Therefore, the origin, nature, and abundance of UDGs are important for understanding dark matter and galaxy formation.
In this project, we analyzed a set of highly sensitive images taken with the Hyper Suprime-Cam (HSC) camera on the Subaru telescope located on Mt. Mauna Kea in Hawaii. HSC offers superior wide-field coverage, allowing observations of large galaxy clusters that span a large portion of the sky. Due to their remarkable sensitivity, these images reveal stars and galaxies both in the foreground and background, which obscure UDGs. Therefore, we developed a special image-cleaning technique to eliminate those contaminating objects. We successfully identified 1,503 UDGs in the Come cluster, one of the prototypal galaxy clusters in the local Universe.
We revealed that the spatial distribution of UDGs closely resembles that of more massive, conventional galaxies, such as elliptical galaxies. Notably, the UDG distribution also shows the known substructures, such as the NGC 4839 subgroup, within the Coma cluster. The similarity in the spatial distribution of UDGs and conventional galaxies suggests that they have formed and evolved in a similar manner, indicating that the extended and diffuse UDGs have not been significantly affected by the strong tidal field within the galaxy cluster.
We also found that the UDG population near the center of the cluster is slightly redder than the rest of the UDG population. This suggests that star formation in the UDGs near the cluster center was halted earlier, though the specific mechanism responsible for this halt remains identified.
Multiple students were actively involved in this project, gaining valuable research experience. A graduate student successfully completed his PhD degree based on the work carried out within this project. Three undergraduate students who worked in this project have gone on to enroll in graduate schools. The new UDG catalog of the Coma cluster has been published in a peer-reviewed journal.
Last Modified: 09/27/2023
Modified by: Jin Koda
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