eDIG-CHANGES I: Extended Hα Emission from the Extraplanar Diffuse Ionized Gas (eDIG) around CHANG-ES Galaxies

Abstract

The extraplanar diffuse ionized gas (eDIG) represents the cool/warm ionized gas reservoir around galaxies. We present a spatial analysis of H$\alpha$ images of 22 nearby edge-on spiral galaxies from the CHANG-ES sample (the eDIG-CHANGES project), taken with the APO 3.5m telescope, in order to study their eDIG. We conduct an exponential fit to the vertical intensity profiles of the sample galaxies, of which 16 can be decomposed into a thin disk plus an extended thick disk component. The median value of the scale height (h) of the extended component is $1.13\pm 0.14$ kpc. We find a tight sublinear correlation between h and the SFR. Moreover, the offset of individual galaxies from the best-fit SFR-h relation shows significant anti-correlation with SFR_SD. This indicates that galaxies with more intense star formation tend to have disproportionately extended eDIG. Combined with data from the literature, we find that the correlations between the eDIG properties and the galaxies' properties extend to broader ranges. We further compare the vertical extension of the eDIG to multi-wavelength measurements of other CGM phases. We find the eDIG to be slightly more extended than the neutral gas (HI 21-cm line), indicating the existence of some extended ionizing sources. Most galaxies have an X-ray scale height smaller than the h, suggesting that the majority of the X-ray emission detected in shallow observations are actually from the thick disk. The h is comparable to the L-band radio continuum scale height, both slightly larger than that at higher frequencies (C-band), where the cooling is stronger and the thermal contribution may be larger. The comparable H$\alpha$ and L-band scale height indicates that the thermal and non-thermal electrons have similar spatial distributions. This further indicates that the thermal gas, the cosmics rays, and the magnetic field may be close to energy equipartition.

References in corpus (10)

• A Spectacular H$\alpha$ Complex in Virgo: Evidence for a Collision Between M86 and NGC 4438 and Implications for Collisional ISM Heating of Ellipticals
• A 100-kiloparsec wind feeding the circumgalactic medium of a massive compact galaxy
• H-alpha emission in local galaxies: star formation, time variability and the diffuse ionized gas
• The Circum-Galactic Medium of MASsive Spirals II: Probing the Nature of Hot Gaseous Halo around the Most Massive Isolated Spiral Galaxies
• CHANG-ES XX. High Resolution Radio Continuum Images of Edge-on Galaxies and their AGNs -- Data Release 3
• Models of Diffuse Hα in the Interstellar Medium: The Relative Contributions from In Situ Ionisation and Dust Scattering
• Testing a Dynamical Equilibrium Model of the Extraplanar Diffuse Ionized Gas in NGC 891
• Detection of non-thermal hard X-ray emission from the "Fermi bubble" in an external galaxy
• CHANG-ES XXV: HI Imaging of Nearby Edge-on Galaxies -- Data Release 4
• A Dynamical Study of Extraplanar Diffuse Ionized Gas in NGC 5775

Cited by in corpus (10)

• Cosmic-Ray Driven Galactic Winds from the Warm Interstellar Medium
• Bidimensional Exploration of the warm-Temperature Ionised gaS (BETIS) II. Revisiting the ionisation mechanism of the extraplanar diffuse ionised gas
• CO-CHANGES I: IRAM 30m CO Observations of Molecular Gas in the Sombrero Galaxy
• CHANG-ES: XXXVI. The thin and thick radio discs
• Extraplanar emission in isolated edge-on late-type galaxies. I. The H$\alpha$ distribution versus to the old and young stellar discs
• Shocked POststarburst Galaxy Survey. IV. Outflows in Shocked Post-Starburst Galaxies Are Not Responsible For Quenching
• The GECKOS Survey: Resolved, multiphase observations of mass-loading and gas density in the galactic wind of NGC 4666
• CO-CHANGES II: spatially resolved IRAM 30M CO line observations of 23 nearby edge-on spiral galaxies
• CHANG-ES XXXVII. Effects of spectral aging on radio scale heights
• Cosmic-ray electron propagation in NGC 3044 from radio continuum observations