Dissecting the Local Environment of FRB 190608 in the Spiral Arm of its Host Galaxy
Jay S. Chittidi, Sunil Simha, Alexandra G. Mannings, J. X. Prochaska, S. D. Ryder, Marc Rafelski, Marcel Neeleman, Jean‐Pierre Macquart, Nicolás Tejos, Regina A. Jorgenson, Cherie K. Day, Lachlan Marnoch, Shivani Bhandari, Adam T. Deller, Hao Qiu, K. W. Bannister, R. M. Shannon, K. E. Heintz
Abstract
Abstract We present a high-resolution analysis of the host galaxy of fast radio burst (FRB) 190608, an SB(r)c galaxy at z = 0.11778 (hereafter HG 190608), to dissect its local environment and its contributions to the FRB properties. Our Hubble Space Telescope Wide Field Camera 3 ultraviolet and visible light image reveals that the subarcsecond localization of FRB 190608 is coincident with a knot of star formation (Σ SFR = 1.5 × 10 −2 M ⊙ yr −1 kpc −2 ) in the northwest spiral arm of HG 190608. Using H β emission present in our Keck Cosmic Web Imager integral field spectrum of the galaxy with a surface brightness of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>μ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> <mml:mi>β</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mo stretchy="false">(</mml:mo> <mml:mn>3.36</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.21</mml:mn> <mml:mo stretchy="false">)</mml:mo> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>17</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em"/> <mml:mi>erg</mml:mi> <mml:mspace width="0.25em"/> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em"/> <mml:msup> <mml:mrow> <mml:mi>cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em"/> <mml:msup> <mml:mrow> <mml:mi>arcsec</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> </mml:math> , we infer an extinction-corrected H α surface brightness and compute a dispersion measure (DM) from the interstellar medium of HG 190608 of DM Host,ISM = 94 ± 38 pc cm −3 . The galaxy rotates with a circular velocity v circ = 141 ± 8 km s −1 at an inclination i gas = 37° ± 3°, giving a dynamical mass <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>halo</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>dyn</mml:mi> </mml:mrow> </mml:msubsup> <mml:mo>≈</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>11.96</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.08</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em"/> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>⊙</mml:mo> </mml:mrow> </mml:msub> </mml:math> . This implies a halo contribution to the DM of DM Host,Halo = 55 ± 25 pc cm −3 subject to assumptions on the density profile and fraction of baryons retained. From the galaxy rotation curve, we infer a bar-induced pattern speed of Ω p = 34 ± 6 km s −1 kpc −1 using linear resonance theory. We then calculate the maximum time since star formation for a progenitor using the furthest distance to the arm’s leading edge within the localization, and find <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>t</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>enc</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>21</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>25</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> Myr. Unlike previous high-resolution studies of FRB environments, we find no evidence of disturbed morphology, emission, or kinematics for FRB 190608.