CHANG-ES XXXII: Spatially Resolved Thermal/Nonthermal Separation from Radio Data Alone -- New Probes into NGC 3044 and NGC 5775
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| Auteurs principaux: | , , , , , , , , |
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| Format: | Preprint |
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2024
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| _version_ | 1866914882850390016 |
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| author | Irwin, Judith Cook, Tanden Stein, Michael Dettmar, Ralf-Juergen Heesen, Volker Wang, Q. Daniel Wiegert, Theresa Stein, Yelena Vargas, Carlos |
| author_facet | Irwin, Judith Cook, Tanden Stein, Michael Dettmar, Ralf-Juergen Heesen, Volker Wang, Q. Daniel Wiegert, Theresa Stein, Yelena Vargas, Carlos |
| contents | We have carried out spatially resolved thermal/nonthermal separation on two edge-on galaxies, NGC~3044 and NGC~5775, using only radio data. Narrow-band imaging within a frequency band that is almost contiguous from 1.25 to 7.02 GHz (L-band, S-band and C-band) has allowed us to fit spectra and construct thermal, nonthermal, and nonthermal spectral index maps. This method does not require any ancillary H$α$ and infrared data, or reliance on dust corrections that are challenging in edge-on galaxies. For NGC~3044, at 15 arcsec resolution, we find a median thermal fraction of $\sim\, 13$\% with an estimated uncertainty in this fraction of $\sim\, 50$\% at 4.13 GHz. This compares well with the H$α$ mixture method results. We uncovered evidence for a vertical outflow feature reaching at least $z\,\sim\,3.5$ kpc in projection above the plane, reminiscent of M82's starburst wind. For the higher SFR galaxy, NGC~5775 at 12 arcsec resolution, we find a median thermal fraction of 44\% at 4.13 GHz with an estimated error on this fraction of 17\%. Both galaxies show a change of slope (flattening) in L-band. These results suggest that a radio-only method for separating thermal from nonthermal emission is not only feasible, but able to reveal new features that might otherwise be obscured in edge-on disks. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2407_16442 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | CHANG-ES XXXII: Spatially Resolved Thermal/Nonthermal Separation from Radio Data Alone -- New Probes into NGC 3044 and NGC 5775 Irwin, Judith Cook, Tanden Stein, Michael Dettmar, Ralf-Juergen Heesen, Volker Wang, Q. Daniel Wiegert, Theresa Stein, Yelena Vargas, Carlos Astrophysics of Galaxies We have carried out spatially resolved thermal/nonthermal separation on two edge-on galaxies, NGC~3044 and NGC~5775, using only radio data. Narrow-band imaging within a frequency band that is almost contiguous from 1.25 to 7.02 GHz (L-band, S-band and C-band) has allowed us to fit spectra and construct thermal, nonthermal, and nonthermal spectral index maps. This method does not require any ancillary H$α$ and infrared data, or reliance on dust corrections that are challenging in edge-on galaxies. For NGC~3044, at 15 arcsec resolution, we find a median thermal fraction of $\sim\, 13$\% with an estimated uncertainty in this fraction of $\sim\, 50$\% at 4.13 GHz. This compares well with the H$α$ mixture method results. We uncovered evidence for a vertical outflow feature reaching at least $z\,\sim\,3.5$ kpc in projection above the plane, reminiscent of M82's starburst wind. For the higher SFR galaxy, NGC~5775 at 12 arcsec resolution, we find a median thermal fraction of 44\% at 4.13 GHz with an estimated error on this fraction of 17\%. Both galaxies show a change of slope (flattening) in L-band. These results suggest that a radio-only method for separating thermal from nonthermal emission is not only feasible, but able to reveal new features that might otherwise be obscured in edge-on disks. |
| title | CHANG-ES XXXII: Spatially Resolved Thermal/Nonthermal Separation from Radio Data Alone -- New Probes into NGC 3044 and NGC 5775 |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2407.16442 |