arXiv subjects

Paul Bennet

Publications and source records attributed to Paul Bennet.

41 records · Page 3Linked to original sources

arXiv2022

AGC 226178 and NGVS 3543: Two deceptive dwarfs towards Virgo

The two sources AGC 226178 and NGVS 3543, an extremely faint, clumpy, blue stellar system and a low surface brightness dwarf spheroidal, are adjacent systems in the direction of the Virgo cluster. Both have been studied in detail previously, with it being suggested that they are unrelated normal dwarf galaxies or that NGVS 3543 recently lost its gas through ram pressure stripping, and that AGC 226178 formed from this stripped gas. However, with HST ACS imaging we demonstrate that the stellar population of NGVS 3543 is inconsistent with being at the distance of the Virgo cluster, and that it is likely a foreground object at approximately 10 Mpc. Whereas the stellar population of AGC 226178 is consistent with it being a very young (10-100 Myr) object in the Virgo cluster. Through a re-analysis of the original ALFALFA HI detection we show that AGC 226178 likely formed from gas stripped from the nearby dwarf galaxy VCC 2034, a hypothesis strengthened by the high metallicity measured with MUSE VLT observations. However, it is unclear whether ram pressure or a tidal interaction is responsible for stripping the gas. AGC 226178 is one of at least five similar objects now known towards Virgo. These objects are all young and unlikely to remain visible for over ~500 Myr, suggesting that they are continually produced in the cluster.

astro-ph.GA↗

arXiv2021

Satellites Around Milky Way Analogs: Tension in the Number and Fraction of Quiescent Satellites Seen in Observations Versus Simulations

We compare the star-forming properties of satellites around Milky Way (MW) analogs from the Stage~II release of the Satellites Around Galactic Analogs Survey (SAGA-II) to those from the APOSTLE and Auriga cosmological zoom-in simulation suites. We use archival GALEX UV imaging as a star-formation indicator for the SAGA-II sample and derive star-formation rates (SFRs) to compare with those from APOSTLE and Auriga. We compare our detection rates from the NUV and FUV bands to the SAGA-II H$α$ detections and find that they are broadly consistent with over $85\%$ of observed satellites detected in all three tracers. We apply the same spatial selection criteria used around SAGA-II hosts to select satellites around the MW-like hosts in APOSTLE and Auriga. We find very good overall agreement in the derived SFRs for the star-forming satellites as well as the number of star-forming satellites per host in observed and simulated samples. However, the number and fraction of quenched satellites in the SAGA-II sample are significantly lower than those in APOSTLE and Auriga below a stellar mass of $M_*\sim10^{8}\,M_{\odot}$, even when the SAGA-II incompleteness and interloper corrections are included. This discrepancy is robust with respect to the resolution of the simulations and persists when alternative star-formation tracers are employed. We posit that this disagreement is not readily explained by vagaries in the observed or simulated samples considered here, suggesting a genuine discrepancy that may inform the physics of satellite populations around MW analogs.

astro-ph.GA↗

arXiv2021

Evidence for Ultra-Diffuse Galaxy Formation Through Tidal Heating of Normal Dwarfs

We have followed up two ultra-diffuse galaxies (UDGs), detected adjacent to stellar streams, with Hubble Space Telescope (HST) imaging and HI mapping with the Jansky Very Large Array (VLA) 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 $5^{+1}_{-2}$, respectively. NGC 2708-Dw1 is undetected in HI down to a 3$σ$ limit of $\log (M_\mathrm{HI}/\mathrm{M_\odot}) = 7.3$, and there is no apparent HI associated with the nearby stellar stream. There is a 2$σ$ HI 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 HI 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 over-luminous ($M_\mathrm{V} = -11.1$) 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.

astro-ph.GA↗

arXiv2019

Neutral Hydrogen Observations of Low Surface Brightness Galaxies around M101 and NGC 5485

We present atomic hydrogen (HI) observations using the Robert C. Byrd Green Bank Telescope along the lines-of-sight to 27 low surface brightness (LSB) dwarf galaxy candidates discovered in optical searches around M101. We detect HI reservoirs in 5 targets and place stringent upper limits on the remaining 22, implying that they are gas poor. The distances to our HI detections range from 7 Mpc --150 Mpc, demonstrating the utility of wide-bandpass HI observations as a follow-up tool. The systemic velocities of 3 detections are consistent with that of the NGC~5485 group behind M101, and we suggest that our 15 non-detections with lower distance limits from the optical are associated with and have been stripped by that group. We find that the gas richnesses of confirmed M101 satellites are broadly consistent with those of the Milky Way satellites, as well as with those of satellites around other hosts of comparable mass, when survey completeness is taken into account. This suggests that satellite quenching and gas stripping proceeds similarly around halos of similar mass, in line with theoretical expectations.

astro-ph.GA↗

arXiv2018

Evidence for Ultra-Diffuse Galaxy `Formation' Through Galaxy Interactions

We report the discovery of two ultra-diffuse galaxies (UDGs) which show clear evidence for association with tidal material and interaction with a larger galaxy halo, found during a search of the Wide portion of the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS). The two new UDGs, NGC2708-Dw1 and NGC5631-Dw1, are faint ($M_g$=$-$13.7 and $-$11.8 mag), extended ($r_h$=2.60 and 2.15 kpc) and have low central surface brightness ($μ(g,0)$=24.9 and 27.3 mag arcsec$^{-2}$), while the stellar stream associated with each has a surface brightness $μ(g)$$\gtrsim$28.2 mag arcsec$^{-2}$. These observations provide evidence that the origin of some UDGs may connect to galaxy interactions, either by transforming normal dwarf galaxies by expanding them, or because UDGs can collapse out of tidal material (i.e. they are tidal dwarf galaxies). Further work is needed to understand the fraction of the UDG population `formed' through galaxy interactions, and wide field searches for diffuse dwarf galaxies will provide further clues to the origin of these enigmatic stellar systems.

astro-ph.GA↗