The Magnetic Fields of Starburst Galaxies. I. Identification and Characterization of the Thermal Polarization in the Galactic Disk and Outflow
| Autor: | Enrique Lopez-Rodriguez |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2023 |
| Předmět: | |
| Zdroj: | The Astrophysical Journal, Vol 953, Iss 1, p 113 (2023) |
| Druh dokumentu: | article |
| ISSN: | 1538-4357 59609494 |
| DOI: | 10.3847/1538-4357/ace110 |
| Popis: | Far-infrared polarized emission by means of magnetically aligned dust grains is an excellent tracer of the magnetic fields (B-fields) in the cold phase of the galactic outflows of starburst galaxies. We present a comprehensive study of the B-fields in three nearby (3.5–17.2 Mpc) starbursts (M82, NGC 253, and NGC 2146) at 5 pc–1.5 kpc resolutions using publicly available 53–890 μ m imaging polarimetric observations with Stratospheric Observatory for Infrared Astronomy/HAWC+, James Clerk Maxwell Telescope/POL-2, and ALMA. We find that the polarized spectral energy distributions (SEDs) of the full galaxies are dominated by the polarized SEDs of the outflows with dust temperatures of ${T}_{{\rm{d}},\mathrm{outflow}}^{\mathrm{PI}}\sim 45$ K and an emissive index of ${\beta }_{\mathrm{outflow}}^{\mathrm{PI}}\sim 2.3$ . The disks are characterized by low ${T}_{{\rm{d}},\mathrm{disk}}^{\mathrm{PI}}=[24,31]$ K and ${\beta }_{\mathrm{disk}}^{\mathrm{PI}}\sim 1$ . We show that disk- and outflow-dominated galaxies can be better distinguished by using polarized SEDs instead of total SEDs. We compute the 53–850 μ m polarization spectrum of the disk and outflow, and find that dust models of the diffuse ISM can reproduce the fairly constant polarization spectrum of the disk, 〈 P _disk 〉 = 1.2% ± 0.5%. The dust models of heterogenous clouds and two-temperature components are required to explain the polarization spectrum of the outflow (2%–4% at 53 μ m, ∼1% at 850 μ m, and a minimum within 89–154 μ m). We conclude that the polarized dust grains in the outflow arise from a dust population with higher dust temperature and emissivities than those from the total flux. The B-fields of the outflows have maximum extensions within 89–214 μ m reaching heights of ∼4 kpc, and have flatter polarized fluxes than total fluxes. The extension of the B-field permeating the circumgalactic medium increases as the star formation rate increases. |
| Databáze: | Directory of Open Access Journals |
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