ODIN: A New Lyman Alpha Blob Selection Method, Sample, and Statistical Analysis at $z\sim3.1$
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| Natura: | Preprint |
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2025
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| author | Moon, Byeongha Yang, Yujin Lee, Kyoung-Soo Gawiser, Eric Dey, Arjun Valdes, Francisco Lang, Dustin Ciardullo, Robin Gronwall, Caryl Zabludoff, Ann Ramakrishnan, Vandana Firestone, Nicole M. Pinarski, Ethan Chang, Seok-jun Guaita, Lucia Hong, Sungryong Hwang, Ho Seong Im, Sang Hyeok Jeong, Woong-Seob Jun, Eunsoo Kim, Seongjae Lee, Jaehyun Lee, Seong-Kook Nagaraj, Gautam Nantais, Julie B. Padilla, Nelson Park, Changbom Song, Hyunmi Troncoso, Paulina |
| author_facet | Moon, Byeongha Yang, Yujin Lee, Kyoung-Soo Gawiser, Eric Dey, Arjun Valdes, Francisco Lang, Dustin Ciardullo, Robin Gronwall, Caryl Zabludoff, Ann Ramakrishnan, Vandana Firestone, Nicole M. Pinarski, Ethan Chang, Seok-jun Guaita, Lucia Hong, Sungryong Hwang, Ho Seong Im, Sang Hyeok Jeong, Woong-Seob Jun, Eunsoo Kim, Seongjae Lee, Jaehyun Lee, Seong-Kook Nagaraj, Gautam Nantais, Julie B. Padilla, Nelson Park, Changbom Song, Hyunmi Troncoso, Paulina |
| contents | Ly$α$ blobs (LABs) are large, spatially extended Ly$α$-emitting objects whose nature remains unclear. Their statistical properties such as number densities and luminosity functions are still uncertain because of small sample sizes and large cosmic variance. The One-hundred-deg$^2$ DECam Imaging in Narrowbands (ODIN) survey, with its large volume, offers an opportunity to overcome these limitations. We describe our LAB selection method and present 112 new LABs in the 9 deg$^2$ E-COSMOS field. We begin with the conventional LAB selection approach, cross-matching LAEs with extended Ly$α$ sources, yielding 89 LAB candidates. To obtain a more complete LAB sample, we introduce a new selection pipeline that models all galaxies detected in deep broadband imaging, subtracts them from the narrowband image, and then directly detects extended Ly$α$ emission. This method successfully identifies 23 additional low-surface-brightness LABs which could otherwise be missed by the conventional method. The number density of ODIN LABs near an ODIN protocluster ($n=7.5\times10^{-5}$ cMpc$^{-3}$) is comparable to that found in the SSA22 proto-cluster and is four times higher than the average across the field. The cumulative Ly$α$ luminosity function within the protocluster regions is similar to that measured for the LABs in the SSA22 proto-cluster, suggesting a large excess of luminous LABs relative to the average field. These findings suggest the Ly$α$ luminosities and number densities of LABs are environment-dependent. ODIN will provide an expansive LAB and protocluster samples across six additional fields and two more redshifts, allowing us to investigate the nature of LABs in relation to their environments. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2512_17368 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | ODIN: A New Lyman Alpha Blob Selection Method, Sample, and Statistical Analysis at $z\sim3.1$ Moon, Byeongha Yang, Yujin Lee, Kyoung-Soo Gawiser, Eric Dey, Arjun Valdes, Francisco Lang, Dustin Ciardullo, Robin Gronwall, Caryl Zabludoff, Ann Ramakrishnan, Vandana Firestone, Nicole M. Pinarski, Ethan Chang, Seok-jun Guaita, Lucia Hong, Sungryong Hwang, Ho Seong Im, Sang Hyeok Jeong, Woong-Seob Jun, Eunsoo Kim, Seongjae Lee, Jaehyun Lee, Seong-Kook Nagaraj, Gautam Nantais, Julie B. Padilla, Nelson Park, Changbom Song, Hyunmi Troncoso, Paulina Astrophysics of Galaxies Ly$α$ blobs (LABs) are large, spatially extended Ly$α$-emitting objects whose nature remains unclear. Their statistical properties such as number densities and luminosity functions are still uncertain because of small sample sizes and large cosmic variance. The One-hundred-deg$^2$ DECam Imaging in Narrowbands (ODIN) survey, with its large volume, offers an opportunity to overcome these limitations. We describe our LAB selection method and present 112 new LABs in the 9 deg$^2$ E-COSMOS field. We begin with the conventional LAB selection approach, cross-matching LAEs with extended Ly$α$ sources, yielding 89 LAB candidates. To obtain a more complete LAB sample, we introduce a new selection pipeline that models all galaxies detected in deep broadband imaging, subtracts them from the narrowband image, and then directly detects extended Ly$α$ emission. This method successfully identifies 23 additional low-surface-brightness LABs which could otherwise be missed by the conventional method. The number density of ODIN LABs near an ODIN protocluster ($n=7.5\times10^{-5}$ cMpc$^{-3}$) is comparable to that found in the SSA22 proto-cluster and is four times higher than the average across the field. The cumulative Ly$α$ luminosity function within the protocluster regions is similar to that measured for the LABs in the SSA22 proto-cluster, suggesting a large excess of luminous LABs relative to the average field. These findings suggest the Ly$α$ luminosities and number densities of LABs are environment-dependent. ODIN will provide an expansive LAB and protocluster samples across six additional fields and two more redshifts, allowing us to investigate the nature of LABs in relation to their environments. |
| title | ODIN: A New Lyman Alpha Blob Selection Method, Sample, and Statistical Analysis at $z\sim3.1$ |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2512.17368 |