A Quenched and Relatively Isolated Dwarf Galaxy in the Local Volume

Abstract An increasing number of discoveries of isolated and quenched dwarf galaxies are challenging the idea that the present-day local environment of low-mass systems is the main determinant of their quenching. We present new Hubble Space Telescope (HST) data of one such system, the dwarf galaxy Canes Venatici C (CVnC). CVnC is a low-mass ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>3</mml:mn> <mml:mo>.</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2.6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>4.2</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>×</mml:mo> <mml:mn>1</mml:mn> <mml:msup> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>6</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="1em"/> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> ) galaxy with a Tip of the Red Giant Branch distance of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>8.4</mml:mn> <mml:msubsup> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.32</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.47</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> Mpc determined from the resolved stars in the HST imaging, which we also use to derive CVnC’s structural parameters. CVnC’s distance places CVnC in the Local Volume and in an isolated environment with the most tidally influential L ⋆ galaxy &gt; 5 R vir away. Additional constraints from the HST color–magnitude diagram, archival far-ultraviolet, and neutral hydrogen (H i ) data show that CVnC is quenched, with no evidence of star formation in the last 100 Myr and no detectable gas (M H i &lt; 1.5 × 10 6 M ⊙ ). Circumstantial evidence suggests that CVnC may have quenched via past interactions with the L ⋆ galaxy NGC 4631 ( L K = 10 10.4 L ⊙ ), and was possibly sent on an extreme backsplash orbit by the tidal dissolution of a subhalo group. However, other quenching mechanisms—such as stripping via the cosmic web—cannot be ruled out. CVnC adds to the growing number of quenched dwarf galaxies in underdense environments, a population that will be critical to defining the mass and environment regimes in which different quenching mechanisms operate.