Hα emission in the outskirts of galaxies at z = 0.4. (14th February 2022)

• Record Type: Journal Article
• Authors: Shimakawa, Rhythm; Tanaka, Masayuki; Kikuta, Satoshi; Hayashi, Masao
• Is Part Of: Publications of the Astronomical Society of Japan. Volume 74:Number 2(2022)
• Page Start: 318
• Page End: 325
• Publication Date: 2022-02-14
• Subjects: galaxies: evolution -- galaxies: formation -- galaxies: general -- galaxies: halos; Astronomy -- Periodicals; 520.5
• DOI: 10.1093/pasj/psab127
• Languages: English
• ISSNs: 0004-6264

Abstract

Abstract: This paper reports detections of Hα emission and stellar continuum out to approximately 30 physical kiloparsecs, and Hα directionality in the outskirts of Hα-emitting galaxies (Hα emitters) at $z$ = 0.4. This research adopts narrow-band selected Hα emitters at $z$ = 0.4 from the emission-line object catalog by Hayashi et al. (2020, PASJ, 72, 86), which is based on data in the Deep and Ultradeep layers of the Hyper Suprime-Cam Subaru Strategic Program. Deep narrow- and broad-band images of 8625 Hα emitters across 16.8 deg 2 enable us to construct deep composite emission-line and continuum images. The stacked images show diffuse Hα emission (down to ∼5 × 10 −20 erg s −1 cm −2 arcsec −2 ) and stellar continuum (down to ∼5 × 10 −22 erg s −1 cm −2 Å −1 arcsec −2 ), extending beyond 10 kpc at stellar masses >10 9 $M_\odot$, parts of which may originate from stellar halos. Those radial profiles are broadly consistent with each other. In addition, we obtain a dependence of the Hα emission on the position angle because relatively higher Hα equivalent width has been detected along the minor-axis towards galaxy disks. While the Hα directionality could be attributed to biconical outflows, further research with hydrodynamic simulations is highly demanded to pin down the exact cause.