Extraplanar emission in isolated edge-on late-type galaxies. I. The H$\alpha$ distribution versus to the old and young stellar discs

• Main Authors: Sardaneta, Minerva M, Amram, Philippe, Rampazzo, Roberto, Rosado, Margarita, Sanchez-Cruces, Monica, Fuentes-Carrera, Isaura, Ghosh, Soumavo
• Format: Journal Article
• Language: English
• Published: 05-01-2024
• Subjects: Physics - Astrophysics of Galaxies
• DOI: 10.48550/arxiv.2401.02876

Isolated galaxies are the ideal reference sample to study the galaxy
structure minimising potential environmental effects. We selected a complete
sample of 14 nearby, late-type, highly inclined ($i\geq80^{\circ}$), isolated
galaxies from the Catalogue of Isolated Galaxies (CIG) which offers a vertical
view of their disc structure. We aim to study extraplanar Diffuse Ionized Gas
(eDIG) by comparing the old and young disc components traced by near-infrared
(NIR) and Ultraviolet (UV) imaging with the H$\alpha$ emission structure. We
obtained H$\alpha$ monochromatic maps from the Fabry-Perot (FP) interferometry,
while the old and young discs structures are obtained from the photometric
analysis of the 2MASS K$_{s}$-band, and GALEX NUV and FUV images, thereby
identifying the stellar disc and whether the eDIG is present. The H$\alpha$
morphology is peculiar in CIG 71, CIG 183, CIG 593 showing clear asymmetries.
In general, geometric parameters (isophotal position angle, peak light
distribution, inclination) measured from H$\alpha$, UV and NIR show minimal
differences (e.g. $\Delta i\leq\pm$10$^{\circ}$), suggesting that interaction
does not play a significant role in shaping the morphology, as expected in
isolated galaxies. From H$\alpha$ maps, the eDIG was detected vertically in 11
out of 14 galaxies. Although the fraction of eDIG is high, the comparison
between our sample and a generic sample of inclined spirals suggests that the
phenomenon is uncorrelated to the galaxy environment. As suggested by the
extraplanar UV emission found in 13 out of 14 galaxies the star formation
extends well beyond the disc defined by the H$\alpha$ map.