TY - JOUR
T1 - Evidence for Ultra-diffuse Galaxy Formation through Tidal Heating of Normal Dwarfs
AU - Jones, Michael G.
AU - Bennet, Paul
AU - Mutlu-Pakdil, Burcin
AU - Sand, David J.
AU - Spekkens, Kristine
AU - Crnojević, Denija
AU - Karunakaran, Ananthan
AU - Zaritsky, Dennis
N1 - Publisher Copyright:
© 2021. The American Astronomical Society. All rights reserved..
PY - 2021/10/1
Y1 - 2021/10/1
N2 - We have followed up two ultra-diffuse galaxies (UDGs), detected adjacent to stellar streams, with Hubble Space Telescope (HST) imaging and H i mapping with the Jansky Very Large Array in order to investigate the possibility that they might have a tidal origin. With the HST F814W and F555W images we measure the globular cluster (GC) counts for NGC 2708-Dw1 and NGC 5631-Dw1 as 2-1+1 and 5-2+1, respectively. NGC 2708-Dw1 is undetected in H i down to a 3σ limit of log (M H i /M o˙) = 7.3, and there is no apparent H i associated with the nearby stellar stream. There is a 2σ H i feature coincident with NGC 5631-Dw1. However, this emission is blended with a large gaseous tail emanating from NGC 5631 and is not necessarily associated with the UDG. The presence of any GCs and the lack of clear H i connections between the UDGs and their parent galaxies strongly disfavor a tidal dwarf galaxy origin, but cannot entirely rule it out. The GC counts are consistent with those of normal dwarf galaxies, and the most probable formation mechanism is one where these UDGs were born as normal dwarfs and were later tidally stripped and heated. We also identify an overluminous (M V = -11.1) GC candidate in NGC 2708-Dw1, which may be a nuclear star cluster transitioning to an ultra-compact dwarf as the surrounding dwarf galaxy gets stripped of stars.
AB - We have followed up two ultra-diffuse galaxies (UDGs), detected adjacent to stellar streams, with Hubble Space Telescope (HST) imaging and H i mapping with the Jansky Very Large Array in order to investigate the possibility that they might have a tidal origin. With the HST F814W and F555W images we measure the globular cluster (GC) counts for NGC 2708-Dw1 and NGC 5631-Dw1 as 2-1+1 and 5-2+1, respectively. NGC 2708-Dw1 is undetected in H i down to a 3σ limit of log (M H i /M o˙) = 7.3, and there is no apparent H i associated with the nearby stellar stream. There is a 2σ H i feature coincident with NGC 5631-Dw1. However, this emission is blended with a large gaseous tail emanating from NGC 5631 and is not necessarily associated with the UDG. The presence of any GCs and the lack of clear H i connections between the UDGs and their parent galaxies strongly disfavor a tidal dwarf galaxy origin, but cannot entirely rule it out. The GC counts are consistent with those of normal dwarf galaxies, and the most probable formation mechanism is one where these UDGs were born as normal dwarfs and were later tidally stripped and heated. We also identify an overluminous (M V = -11.1) GC candidate in NGC 2708-Dw1, which may be a nuclear star cluster transitioning to an ultra-compact dwarf as the surrounding dwarf galaxy gets stripped of stars.
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U2 - 10.3847/1538-4357/ac0975
DO - 10.3847/1538-4357/ac0975
M3 - Article
AN - SCOPUS:85116887279
SN - 0004-637X
VL - 919
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 72
ER -