Abstract We present deep Hubble Space Telescope (HST) imaging of five faint dwarf galaxies associated with the nearby spiral NGC 253 (D ≈ 3.5 Mpc). Three of these are newly discovered dwarf galaxies, while all five were found in the Panoramic Imaging Survey of Centaurus and Sculptor, a Magellan+Megacam survey to identify faint dwarfs and other substructures in resolved stellar light around massive galaxies outside of the Local Group. Our HST data reach ≳3 magnitudes below the tip of the red giant branch for each dwarf, allowing us to derive their distances, structural parameters, and luminosities. All five systems contain mostly old, metal-poor stellar populations (age ∼12 Gyr, [M/H] ≲ −1.5) and have sizes ( r h ∼ 110–3000 pc) and luminosities ( M V ∼ −7 to −12 mag) largely consistent with Local Group dwarfs. The three new NGC 253 satellites are among the faintest systems discovered beyond the Local Group. We also use archival H i data to place limits on the gas content of our discoveries. Deep imaging surveys such as our program around NGC 253 promise to elucidate the faint end of the satellite luminosity function and its scatter across a range of galaxy masses, morphologies, and environments in the decade to come.
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H i properties of satellite galaxies around local volume hosts
We present neutral atomic hydrogen (H i) observations using the Robert C. Byrd Green Bank Telescope along the lines of sight to 49 confirmed or possible dwarf satellite galaxies around eight Local Volume systems (M104, M51, NGC 1023, NGC 1156, NGC 2903, NGC 4258, NGC 4565, and NGC 4631). We detect the H i reservoirs of two candidates (dw0934+2204 and dw1238−1122) and find them to be background sources relative to their nearest foreground host systems. The remaining 47 satellite candidates are not detected in H i, and we place stringent 5σ upper limits on their H i mass. We note that some (15/47) of our non-detections stem from satellites being occluded by their putative host’s H i emission. In addition to these new observations, we compile literature estimates on the H i mass for an additional 17 satellites. We compare the H i properties of these satellites to those within the Local Group, finding broad agreement between them. Crucially, these observations probe a ‘transition’ region between −10 ≳ MV ≳ −14 where we see a mixture of gas-rich and gas-poor satellites. While there are many gas-poor satellites within this region, some are gas-rich and this suggests that the transition towards predominantly gas-rich satellites occurs at LV ∼ 107L⊙, in line with simulations. The observations presented here are a key step toward characterizing the properties of dwarf satellite galaxies around Local Volume systems and future wide-field radio surveys with higher angular resolution (e.g. WALLABY) will vastly improve upon the study of such systems.
more » « less- NSF-PAR ID:
- 10370678
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 516
- Issue:
- 2
- ISSN:
- 0035-8711
- Page Range / eLocation ID:
- p. 1741-1751
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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