Chang, Yu-YenLe Floc'h, EmericJuneau, Stephanieda Cunha, ElisabeteSalvato, MaraDekel, ACivano, FrancescaMarchesi, StefanoSuh, HyewonWang, Wei-Hao2022-06-282022-06-280004-637Xhttp://hdl.handle.net/1885/268533We present rest-frame far-infrared (FIR) and optical size measurements of active galactic nucleus (AGN) hosts and star-forming galaxies (SFGs) in the COSMOS field, enabled by high-resolution Atacama Large Millimeter/ submillimeter Array (ALMA)/1 mm (0 1-0 4) and Hubble Space Telescope (HST)/F814W imaging (∼0 1). Our sample includes 27 galaxies at z < 2.5, classified as infrared-selected AGN (three sources), X-ray selected AGN (four sources), and non-AGN SFGs (20 sources), for which high-resolution Band 6/7 ALMA images are available at 1 mm from our own observing program as well as archival observations. The sizes and star formation rate surface densities measured from both ALMA/1 mm and HST/F814W images show that obscured AGN host galaxies are more compact than non-AGN SFGs at similar redshift and stellar mass. This result suggests that the obscured accretion phase may be related to galaxies experiencing a compaction of their gaseous component, which could be associated with enhanced central star formation before a subsequent quenching driving the formation of compact passive galaxies. Moreover, most of the detected and stacked rest-frame FIR sizes of AGNs in our sample are similar or more compact than their rest-frame optical sizes, which is consistent with recent results of ALMAdetected sources. This might be explained by the fact that the dusty starbursts take place in the compact regions, and suggests that the star formation mechanisms in the compact regions of AGN hosts are similar to those observed in SFGs observed with ALMA.Y.Y.C. acknowledges financial support from the Ministry of Science and Technology of Taiwan grant (105-2112-M-001-029-MY3 and 108-2112-M001-014-), and the Agence Nationale de la Recherche (contract #ANR-12-JS05-0008-01). E.d.C. gratefully acknowledges the Australian Research Council as the recipient of a Future Fellowship (project FT150100079). This paper makes use of the following ALMA data: ADS/JAO.ALMA #2013.1.00034. S, #2015.1.00026.S, #2016.1.00478.S, #2016.1.00735.S, #2016.1.00778.S, #2016.1.01355.S, #2016.1.01426.S, and #2016.1.01604.S. ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chileapplication/pdfen-AU© 2020. The American Astronomical Society.Active galactic nucleiAGN host galaxiesStar formationGalaxy structureGalaxy formationGalaxy evolution202010.3847/1538-4357/ab595b2021-08-01