Detalles de publicación

PP 026078

Clumpy Disk, Interloper, or Merger? Nature of a Distant Galaxy Pair at 5 kpc Projected Separation

Hajar Aziz (1,2), Vivian U (3,1), Archana Aravindan (4,5,2), Raymond P. Remigio (1), Gabriela Canalizo (2), Justin A. Kader (1), Marina Bianchin (6,7,1), Yiqing Song (8,9,10), Tianmu Gao (11,12), Jeff Rich (13), Rosalie McGurk (14)
(1) University of California Irvine, (2) University of California Riverside, (3) IPAC, (4) Department of Astronomy, The University of Texas at Austin, (5) Cosmic Frontier Center, The University of Texas at Austin, (6) IAC, (7) ULL, (8) ESO, (9) Joint ALMA Observatory, (10) Max-Planck-Institut fur Radioastronomie, (11) Australian National University, (12) ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), (13) The Observatories of the Carnegie Institution for Science, (14) W. M. Keck Observatory
Abstract:We present the morphological, photometric, and spectroscopic properties of a z ~ 1 galaxy, "lil gal", serendipitously detected in JWST Mid Infrared Instrument (MIRI) images of nearby galaxy VV 340. In the MIRI F560W and F770W images, we identify what appears to be a spiral galaxy with a central bulge. However, in the F1500W image, a second peak appears ~0.7" northwest (NW) from the central bulge, calling into question the nature of this source as a clumpy disk, a high-redshift interloper, or a galaxy merger. Multi-band analyses of the three MIRI and four Hubble Space Telescope (HST) images suggest a photometric redshift of ~0.92. Spectroscopic analyses of data from the Keck Near-Infrared Echellette Spectrometer (NIRES) reveal two sets of [N II] and H-alpha emission lines corresponding to the two observed sources. A redshift of z = 0.9248 is identified for the NW companion. Fainter emission lines are identified from the underlying galaxy at z = 0.9225, suggesting a merging galaxy pair at a projected separation of ~5 kpc. From the emission line ratios from Keck NIRES and Keck Cosmic Web Imager (KCWI) spectra, we classify the system as hosting regions of active star formation, likely attributed to merger-induced starburst activity. The results demonstrate the necessity of resolved, spectroscopic follow-up analyses of galaxies found in deep JWST images to disentangle the role of galaxy mergers from clumpy disk galaxies at z ~ 1 to cosmic noon and beyond.

 
Aceptado para publicación en ApJ | Enviado el 2026-06-26 | Proyecto P/301404