Discovery of a new Local Group Dwarf Galaxy Candidate in UNIONS: Boötes V

Simon E. T. Smith; Jaclyn Jensen; Joel Roediger; Federico Sestito; Christian R. Hayes; Alan W. McConnachie; Jean-Charles Cuillandre; Stephen Gwyn; Eugene Magnier; Ken Chambers; Francois Hammer; Mike Hudson; Nicolas Martin; Julio Navarro; Douglas Scott

doi:10.3847/1538-3881/acdd77

Discovery of a new Local Group Dwarf Galaxy Candidate in UNIONS: Boötes V

Simon E. T. Smith, Jaclyn Jensen, Joel Roediger, Federico Sestito, Christian R. Hayes, Alan W. McConnachie, Jean-Charles Cuillandre, Stephen Gwyn, Eugene Magnier, Ken Chambers, Francois Hammer, Mike Hudson, Nicolas Martin, Julio Navarro, Douglas Scott

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Abstract

We present the discovery of Bo\"otes V, a new ultra-faint dwarf galaxy candidate. This satellite is detected as a resolved overdensity of stars during an ongoing search for new Local Group dwarf galaxy candidates in the UNIONS photometric dataset. It has a physical half-light radius of 26.9$^{+7.5}_{-5.4}$ pc, a $V$-band magnitude of $-$4.5 $\pm$ 0.4 mag, and resides at a heliocentric distance of approximately 100 kpc. We use Gaia DR3 astrometry to identify member stars, characterize the systemic proper motion, and confirm the reality of this faint stellar system. The brightest star in this system was followed up using Gemini GMOS-N long-slit spectroscopy and is measured to have a metallicity of [Fe/H] $=$ $-$2.85 $\pm$ 0.10 dex and a heliocentric radial velocity of $v_r$ = 5.1 $\pm$ 13.4 km s$^{-1}$. Bo\"otes V is larger (in terms of scale radius), more distant, and more metal-poor than the vast majority of globular clusters. It is likely that Bo\"otes V is an ultra-faint dwarf galaxy, though future spectroscopic studies will be necessary to definitively classify this object.

Original language	English
Journal	The Astrophysical Journal
DOIs	https://doi.org/10.3847/1538-3881/acdd77
Publication status	Published - 17 Sept 2022

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astro-ph.GA

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10.3847/1538-3881/acdd77

2209.08242v2

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@article{ef6eee39a46f47e3baf89807e84f1ad5,

title = "Discovery of a new Local Group Dwarf Galaxy Candidate in UNIONS: Bo{\"o}tes V",

abstract = " We present the discovery of Bo\{"}otes V, a new ultra-faint dwarf galaxy candidate. This satellite is detected as a resolved overdensity of stars during an ongoing search for new Local Group dwarf galaxy candidates in the UNIONS photometric dataset. It has a physical half-light radius of 26.9$^{+7.5}_{-5.4}$ pc, a $V$-band magnitude of $-$4.5 $\pm$ 0.4 mag, and resides at a heliocentric distance of approximately 100 kpc. We use Gaia DR3 astrometry to identify member stars, characterize the systemic proper motion, and confirm the reality of this faint stellar system. The brightest star in this system was followed up using Gemini GMOS-N long-slit spectroscopy and is measured to have a metallicity of [Fe/H] $=$ $-$2.85 $\pm$ 0.10 dex and a heliocentric radial velocity of $v_r$ = 5.1 $\pm$ 13.4 km s$^{-1}$. Bo\{"}otes V is larger (in terms of scale radius), more distant, and more metal-poor than the vast majority of globular clusters. It is likely that Bo\{"}otes V is an ultra-faint dwarf galaxy, though future spectroscopic studies will be necessary to definitively classify this object. ",

keywords = "astro-ph.GA",

author = "Smith, {Simon E. T.} and Jaclyn Jensen and Joel Roediger and Federico Sestito and Hayes, {Christian R.} and McConnachie, {Alan W.} and Jean-Charles Cuillandre and Stephen Gwyn and Eugene Magnier and Ken Chambers and Francois Hammer and Mike Hudson and Nicolas Martin and Julio Navarro and Douglas Scott",

note = "13 pages, 7 figures, 3 tables. Accepted for publication in the AAS Journals. Please note that this paper was submitted in coordination with the work of William Cerny et al. 2022. These authors independently discovered this same satellite so our two research groups have coordinated the submission of these discovery papers",

year = "2022",

month = sep,

day = "17",

doi = "10.3847/1538-3881/acdd77",

language = "English",

journal = "The Astrophysical Journal",

issn = "0004-637X",

publisher = "IOP Publishing Ltd.",

}

TY - JOUR

T1 - Discovery of a new Local Group Dwarf Galaxy Candidate in UNIONS

T2 - Boötes V

AU - Smith, Simon E. T.

AU - Jensen, Jaclyn

AU - Roediger, Joel

AU - Sestito, Federico

AU - Hayes, Christian R.

AU - McConnachie, Alan W.

AU - Cuillandre, Jean-Charles

AU - Gwyn, Stephen

AU - Magnier, Eugene

AU - Chambers, Ken

AU - Hammer, Francois

AU - Hudson, Mike

AU - Martin, Nicolas

AU - Navarro, Julio

AU - Scott, Douglas

N1 - 13 pages, 7 figures, 3 tables. Accepted for publication in the AAS Journals. Please note that this paper was submitted in coordination with the work of William Cerny et al. 2022. These authors independently discovered this same satellite so our two research groups have coordinated the submission of these discovery papers

PY - 2022/9/17

Y1 - 2022/9/17

N2 - We present the discovery of Bo\"otes V, a new ultra-faint dwarf galaxy candidate. This satellite is detected as a resolved overdensity of stars during an ongoing search for new Local Group dwarf galaxy candidates in the UNIONS photometric dataset. It has a physical half-light radius of 26.9$^{+7.5}_{-5.4}$ pc, a $V$-band magnitude of $-$4.5 $\pm$ 0.4 mag, and resides at a heliocentric distance of approximately 100 kpc. We use Gaia DR3 astrometry to identify member stars, characterize the systemic proper motion, and confirm the reality of this faint stellar system. The brightest star in this system was followed up using Gemini GMOS-N long-slit spectroscopy and is measured to have a metallicity of [Fe/H] $=$ $-$2.85 $\pm$ 0.10 dex and a heliocentric radial velocity of $v_r$ = 5.1 $\pm$ 13.4 km s$^{-1}$. Bo\"otes V is larger (in terms of scale radius), more distant, and more metal-poor than the vast majority of globular clusters. It is likely that Bo\"otes V is an ultra-faint dwarf galaxy, though future spectroscopic studies will be necessary to definitively classify this object.

AB - We present the discovery of Bo\"otes V, a new ultra-faint dwarf galaxy candidate. This satellite is detected as a resolved overdensity of stars during an ongoing search for new Local Group dwarf galaxy candidates in the UNIONS photometric dataset. It has a physical half-light radius of 26.9$^{+7.5}_{-5.4}$ pc, a $V$-band magnitude of $-$4.5 $\pm$ 0.4 mag, and resides at a heliocentric distance of approximately 100 kpc. We use Gaia DR3 astrometry to identify member stars, characterize the systemic proper motion, and confirm the reality of this faint stellar system. The brightest star in this system was followed up using Gemini GMOS-N long-slit spectroscopy and is measured to have a metallicity of [Fe/H] $=$ $-$2.85 $\pm$ 0.10 dex and a heliocentric radial velocity of $v_r$ = 5.1 $\pm$ 13.4 km s$^{-1}$. Bo\"otes V is larger (in terms of scale radius), more distant, and more metal-poor than the vast majority of globular clusters. It is likely that Bo\"otes V is an ultra-faint dwarf galaxy, though future spectroscopic studies will be necessary to definitively classify this object.

KW - astro-ph.GA

U2 - 10.3847/1538-3881/acdd77

DO - 10.3847/1538-3881/acdd77

M3 - Article

SN - 0004-637X

JO - The Astrophysical Journal

JF - The Astrophysical Journal

ER -

Discovery of a new Local Group Dwarf Galaxy Candidate in UNIONS: Boötes V

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