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HII regions in NGC 628: the view of two catalogs

Ksenia I. Smirnova, Dmitri S. Wiebe

TL;DR

The paper compares two automated HII-region catalogs for NGC 628 (Congiu and Groves) to assess cross-catalog consistency. It analyzes multiwavelength fluxes (7.7 μm, 21 μm, Hα, CO) and kinematic line widths (FWHM) after instrumental corrections to evaluate similarities and differences. The study finds substantial overlap but notable spatial and classification discrepancies, with Groves regions generally having higher FWHM and some regions likely representing shocks rather than classical HII regions. These results inform catalog selection and interpretation in PHANGS-like, multiwavelength studies of star formation.

Abstract

The study is devoted to comparing the parameters of the interstellar medium of HII regions in the Kongiu and Groves catalogs for the galaxy NGC 628. The article analyzes the characteristics of star-forming regions, including a comparison of radiation fluxes in the ranges of 7.7 $μ$m and 21 $μ$m and in the H$α$, H$β$, OIII and CO lines, calculating the kinematic parameters (FWHM) for the lines, and analyzing the spatial distribution of regions for both catalogs. The results of the study showed that the regions from the Groves catalog demonstrate higher line widths compared to the Kongiu catalog. Signs of possible misidentified classification of some regions from the Groves catalog were revealed: there is a possibility that some of them are not HII regions, but shock ionization regions.

HII regions in NGC 628: the view of two catalogs

TL;DR

The paper compares two automated HII-region catalogs for NGC 628 (Congiu and Groves) to assess cross-catalog consistency. It analyzes multiwavelength fluxes (7.7 μm, 21 μm, Hα, CO) and kinematic line widths (FWHM) after instrumental corrections to evaluate similarities and differences. The study finds substantial overlap but notable spatial and classification discrepancies, with Groves regions generally having higher FWHM and some regions likely representing shocks rather than classical HII regions. These results inform catalog selection and interpretation in PHANGS-like, multiwavelength studies of star formation.

Abstract

The study is devoted to comparing the parameters of the interstellar medium of HII regions in the Kongiu and Groves catalogs for the galaxy NGC 628. The article analyzes the characteristics of star-forming regions, including a comparison of radiation fluxes in the ranges of 7.7 m and 21 m and in the H, H, OIII and CO lines, calculating the kinematic parameters (FWHM) for the lines, and analyzing the spatial distribution of regions for both catalogs. The results of the study showed that the regions from the Groves catalog demonstrate higher line widths compared to the Kongiu catalog. Signs of possible misidentified classification of some regions from the Groves catalog were revealed: there is a possibility that some of them are not HII regions, but shock ionization regions.
Paper Structure (6 sections, 4 figures)

This paper contains 6 sections, 4 figures.

Table of Contents

  1. Introduction
  2. Catalogs
  3. RESULTS
  4. Location of HII regions
  5. Fluxes and line profiles
  6. Conclusions

Figures (4)

  • Figure 1: Locations of HII regions in NGC 628 according to the Congiu and Groves catalogs.
  • Figure 2: Relation between the FWHM of H$\beta$ lines on the H$\alpha$ lines for the selected regions: HII regions from the Groves catalog (red dots), HII regions from the Congiu catalog (blue dots), shock ionization regions from the Congiu catalog (green dots).
  • Figure 3: Relation between the OIII and H$\alpha$ line FWHMs for star-forming regions of the Groves (red dots) and Congiu (blue dots) catalogs.
  • Figure 4: Line profiles H$\alpha$, H$\beta$ and OIII of one of the regions of the galaxy NGC628. The line profiles were artificially brought to one center.