Constraining the mass of the M31 ionized baryon Halo using CHIME/FRB Catalog 2
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| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , |
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| Format: | Preprint |
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2026
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| author | Kahinga, Lordrick A. Prochaska, J. Xavier Simha, Sunil Leung, Calvin Cook, Amanda C. Craiu, Radu V. Eadie, Gwendolyn Fonseca, Emmanuel Gaensler, B. M. Kaspi, Victoria M. Khan, Afrokk Kharel, Bikash Lanman, Adam E. Main, Robert A. Mas-Ribas, Lluis Masui, Kiyoshi W. Scholz, Paul Pandhi, Ayush Patil, Swarali Shivraj Pearlman, Aaron B. Shin, K. Siegel, Seth R. Smith, Kendrick Woodland, Michele |
| author_facet | Kahinga, Lordrick A. Prochaska, J. Xavier Simha, Sunil Leung, Calvin Cook, Amanda C. Craiu, Radu V. Eadie, Gwendolyn Fonseca, Emmanuel Gaensler, B. M. Kaspi, Victoria M. Khan, Afrokk Kharel, Bikash Lanman, Adam E. Main, Robert A. Mas-Ribas, Lluis Masui, Kiyoshi W. Scholz, Paul Pandhi, Ayush Patil, Swarali Shivraj Pearlman, Aaron B. Shin, K. Siegel, Seth R. Smith, Kendrick Woodland, Michele |
| contents | The circumgalactic medium (CGM) surrounding galaxies is believed to be a significant reservoir of baryons, yet its total mass remains poorly constrained. We present a novel approach to probe the CGM of the Andromeda galaxy (M31) using fast radio bursts (FRBs) from the CHIME/FRB Catalog 2. By comparing the dispersion measures (DMs) of 171 FRBs whose sightlines intersect M31's halo (within $r_{\rm vir}= 302\,\mathrm{kpc}$) to a control sample of 684 FRBs, we estimate the DM contribution from M31's CGM. We find evidence for an excess DM of $δ\mathrm{DM} = 5.9$--$59.6\,\mathrm{pc\,cm^{-3}}$ in the inner halo ($\approx 0$--$151\,\mathrm{kpc}$) and $δ\mathrm{DM} = 25.7$--$64.6\,\mathrm{pc\,cm^{-3}}$ in the outer halo ($\approx 151$--$302\,\mathrm{kpc}$). Using a generalized halo model parameterized by a closure radius $r_{\mathrm{close}}$, we constrain the baryon distribution and infer a best-fit value for $r_{\mathrm{close}}$ to be $9.2^{+9.9}_{-4.9}\,r_{\rm vir}$ ($1σ$), corresponding to a total CGM mass of $M_{b,\mathrm{halo}} = 18.6^{+7.9}_{-8.4} \times 10^{10}\,M_\odot$. Our results suggest that M31 may harbor a substantial fraction of its cosmic baryon budget in diffuse, ionized gas. This work demonstrates the potential of FRBs as a powerful tool for studying the CGM of nearby galaxies, with future larger samples expected to provide tighter constraints on the baryon content of galactic halos. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2602_23749 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Constraining the mass of the M31 ionized baryon Halo using CHIME/FRB Catalog 2 Kahinga, Lordrick A. Prochaska, J. Xavier Simha, Sunil Leung, Calvin Cook, Amanda C. Craiu, Radu V. Eadie, Gwendolyn Fonseca, Emmanuel Gaensler, B. M. Kaspi, Victoria M. Khan, Afrokk Kharel, Bikash Lanman, Adam E. Main, Robert A. Mas-Ribas, Lluis Masui, Kiyoshi W. Scholz, Paul Pandhi, Ayush Patil, Swarali Shivraj Pearlman, Aaron B. Shin, K. Siegel, Seth R. Smith, Kendrick Woodland, Michele Astrophysics of Galaxies The circumgalactic medium (CGM) surrounding galaxies is believed to be a significant reservoir of baryons, yet its total mass remains poorly constrained. We present a novel approach to probe the CGM of the Andromeda galaxy (M31) using fast radio bursts (FRBs) from the CHIME/FRB Catalog 2. By comparing the dispersion measures (DMs) of 171 FRBs whose sightlines intersect M31's halo (within $r_{\rm vir}= 302\,\mathrm{kpc}$) to a control sample of 684 FRBs, we estimate the DM contribution from M31's CGM. We find evidence for an excess DM of $δ\mathrm{DM} = 5.9$--$59.6\,\mathrm{pc\,cm^{-3}}$ in the inner halo ($\approx 0$--$151\,\mathrm{kpc}$) and $δ\mathrm{DM} = 25.7$--$64.6\,\mathrm{pc\,cm^{-3}}$ in the outer halo ($\approx 151$--$302\,\mathrm{kpc}$). Using a generalized halo model parameterized by a closure radius $r_{\mathrm{close}}$, we constrain the baryon distribution and infer a best-fit value for $r_{\mathrm{close}}$ to be $9.2^{+9.9}_{-4.9}\,r_{\rm vir}$ ($1σ$), corresponding to a total CGM mass of $M_{b,\mathrm{halo}} = 18.6^{+7.9}_{-8.4} \times 10^{10}\,M_\odot$. Our results suggest that M31 may harbor a substantial fraction of its cosmic baryon budget in diffuse, ionized gas. This work demonstrates the potential of FRBs as a powerful tool for studying the CGM of nearby galaxies, with future larger samples expected to provide tighter constraints on the baryon content of galactic halos. |
| title | Constraining the mass of the M31 ionized baryon Halo using CHIME/FRB Catalog 2 |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2602.23749 |