On the Evidence for Molecular Outflows in High-redshift Dusty Star-forming Galaxies
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arXiv
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| Natura: | Preprint |
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2024
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| _version_ | 1866911802657341440 |
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| author | Nianias, James Lim, Jeremy Yeung, Michael |
| author_facet | Nianias, James Lim, Jeremy Yeung, Michael |
| contents | Galactic-scale outflows of molecular gas from star-forming galaxies constitute the most direct evidence for regulation of star formation. In the early universe ($ z > 4 $), such outflows have recently been inferred from gravitationally-lensed dusty star-forming galaxies (DSFGs) based on ubiquitous detections of OH absorption extending to more blueshifted velocities than [CII] or CO emission in spatially-integrated spectra. Because these lines are redshifted to sub-mm wavelengths, such measurements require careful corrections for atmospheric absorption lines, and a proper accounting of sometimes large variations in measurement uncertainties over these lines. Taking these factors into consideration, we re-analyze OH and [CII] data taken with ALMA for the five sources where such data is available, of which four were categorised as exhibiting outflows. Based on their spatially-integrated spectra alone, we find statistically significant ($ \geq 3 σ$) OH absorption more blueshifted than [CII] emission in only one source. By contrast, searching channel maps for signals diluted below the detection threshold in spatially-integrated spectra, we find evidence for a separate kinematic component in OH absorption in all five sources in the form of: (i) more blueshifted OH absorption than [CII] emission and/or (ii) a component in OH absorption exhibiting a different spatio-kinematic pattern than [CII] emission, the latter presumably tracing gas in a rotating disc. Providing a more complete and accurate assessment of molecular outflows in gravitationally-lensed DSFGs, we suggest methods to better assess the precision of corrections for atmospheric absorption and to more accurately measure the source continuum in future observations. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2403_09104 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | On the Evidence for Molecular Outflows in High-redshift Dusty Star-forming Galaxies Nianias, James Lim, Jeremy Yeung, Michael Astrophysics of Galaxies Galactic-scale outflows of molecular gas from star-forming galaxies constitute the most direct evidence for regulation of star formation. In the early universe ($ z > 4 $), such outflows have recently been inferred from gravitationally-lensed dusty star-forming galaxies (DSFGs) based on ubiquitous detections of OH absorption extending to more blueshifted velocities than [CII] or CO emission in spatially-integrated spectra. Because these lines are redshifted to sub-mm wavelengths, such measurements require careful corrections for atmospheric absorption lines, and a proper accounting of sometimes large variations in measurement uncertainties over these lines. Taking these factors into consideration, we re-analyze OH and [CII] data taken with ALMA for the five sources where such data is available, of which four were categorised as exhibiting outflows. Based on their spatially-integrated spectra alone, we find statistically significant ($ \geq 3 σ$) OH absorption more blueshifted than [CII] emission in only one source. By contrast, searching channel maps for signals diluted below the detection threshold in spatially-integrated spectra, we find evidence for a separate kinematic component in OH absorption in all five sources in the form of: (i) more blueshifted OH absorption than [CII] emission and/or (ii) a component in OH absorption exhibiting a different spatio-kinematic pattern than [CII] emission, the latter presumably tracing gas in a rotating disc. Providing a more complete and accurate assessment of molecular outflows in gravitationally-lensed DSFGs, we suggest methods to better assess the precision of corrections for atmospheric absorption and to more accurately measure the source continuum in future observations. |
| title | On the Evidence for Molecular Outflows in High-redshift Dusty Star-forming Galaxies |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2403.09104 |