A Large Molecular Gas Reservoir in the Protocluster SPT2349$-$56 at $z\,{=}\,4.3$
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| Natura: | Preprint |
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2024
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| author | Zhou, Dazhi Chapman, Scott C. Sulzenauer, Nikolaus Hill, Ryley Aravena, Manuel Araya-Araya, Pablo Cathey, Jared Marrone, Daniel P. Phadke, Kedar A. Reuter, Cassie Solimano, Manuel Spilker, Justin S. Vieira, Joaquin D. Vizgan, David Wang, George C. P. Weiss, Axel |
| author_facet | Zhou, Dazhi Chapman, Scott C. Sulzenauer, Nikolaus Hill, Ryley Aravena, Manuel Araya-Araya, Pablo Cathey, Jared Marrone, Daniel P. Phadke, Kedar A. Reuter, Cassie Solimano, Manuel Spilker, Justin S. Vieira, Joaquin D. Vizgan, David Wang, George C. P. Weiss, Axel |
| contents | We present Atacama Compact Array (ACA) Band-3 observations of the protocluster SPT2349$-$56, an extreme system hosting ${\gtrsim}\,12$ submillimeter galaxies (SMGs) at $z\,{=}\,4.3$, to study its integrated molecular gas content via CO(4-3) and long-wavelength dust continuum. The $\sim$30-hour integration represents one of the longest exposures yet taken on a single pointing with the ACA 7-m. The low-resolution ACA data ($21.0''\,{\times}\,12.2''$) reveal a 75% excess CO(4-3) flux compared to the sum of individual sources detected in higher-resolution Atacama Large Millimeter Array (ALMA) data ($1.0''\,{\times}\,0.8''$). Our work also reveals a similar result by tapering the ALMA data to $10''$. In contrast, the 3.2mm dust continuum shows little discrepancy between ACA and ALMA. A single-dish [CII] spectrum obtained by APEX/FLASH supports the ACA CO(4-3) result, revealing a large excess in [CII] emission relative to ALMA. The missing flux is unlikely due to undetected faint sources but instead suggests that high-resolution ALMA observations might miss extended and low-surface-brightness gas. Such emission could originate from the circum-galactic medium (CGM) or the pre-heated proto-intracluster medium (proto-ICM). If this molecular gas reservoir replenishes the star formation fuel, the overall depletion timescale will exceed 400Myr, reducing the requirement for the simultaneous SMG activity in SPT2349$-$56. Our results highlight the role of an extended gas reservoir in sustaining a high star formation rate (SFR) in SPT2349$-$56, and potentially establishing the ICM during the transition phase to a mature cluster. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2412_17980 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | A Large Molecular Gas Reservoir in the Protocluster SPT2349$-$56 at $z\,{=}\,4.3$ Zhou, Dazhi Chapman, Scott C. Sulzenauer, Nikolaus Hill, Ryley Aravena, Manuel Araya-Araya, Pablo Cathey, Jared Marrone, Daniel P. Phadke, Kedar A. Reuter, Cassie Solimano, Manuel Spilker, Justin S. Vieira, Joaquin D. Vizgan, David Wang, George C. P. Weiss, Axel Astrophysics of Galaxies We present Atacama Compact Array (ACA) Band-3 observations of the protocluster SPT2349$-$56, an extreme system hosting ${\gtrsim}\,12$ submillimeter galaxies (SMGs) at $z\,{=}\,4.3$, to study its integrated molecular gas content via CO(4-3) and long-wavelength dust continuum. The $\sim$30-hour integration represents one of the longest exposures yet taken on a single pointing with the ACA 7-m. The low-resolution ACA data ($21.0''\,{\times}\,12.2''$) reveal a 75% excess CO(4-3) flux compared to the sum of individual sources detected in higher-resolution Atacama Large Millimeter Array (ALMA) data ($1.0''\,{\times}\,0.8''$). Our work also reveals a similar result by tapering the ALMA data to $10''$. In contrast, the 3.2mm dust continuum shows little discrepancy between ACA and ALMA. A single-dish [CII] spectrum obtained by APEX/FLASH supports the ACA CO(4-3) result, revealing a large excess in [CII] emission relative to ALMA. The missing flux is unlikely due to undetected faint sources but instead suggests that high-resolution ALMA observations might miss extended and low-surface-brightness gas. Such emission could originate from the circum-galactic medium (CGM) or the pre-heated proto-intracluster medium (proto-ICM). If this molecular gas reservoir replenishes the star formation fuel, the overall depletion timescale will exceed 400Myr, reducing the requirement for the simultaneous SMG activity in SPT2349$-$56. Our results highlight the role of an extended gas reservoir in sustaining a high star formation rate (SFR) in SPT2349$-$56, and potentially establishing the ICM during the transition phase to a mature cluster. |
| title | A Large Molecular Gas Reservoir in the Protocluster SPT2349$-$56 at $z\,{=}\,4.3$ |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2412.17980 |