arXiv subjects

Helmut Dannerbauer

Publications and source records attributed to Helmut Dannerbauer.

At least 19 recordsLinked to original sources

arXiv2026

Spider-Webb: enhanced star formation in low-mass galaxies within the Spiderweb protocluster revealed by JWST Pa$\beta$ narrow-band imaging

Understanding the role of the environment in galaxy evolution is key to revealing the physical processes that regulate galaxy growth. We study the star formation activity of \pab\ emitters (PBEs) in the Spiderweb protocluster at $z=2.16$ using \textit{James Webb Space Telescope}/NIRCam narrow-band imaging. To investigate the environmental dependence of star formation, we derive star formation rates (SFRs) from the \pab\ emission line and compare SFRs in the Spiderweb protocluster with those in the field. Our main finding is that low-mass PBEs ($M_\star < 10^9\,M_\odot$) in the Spiderweb protocluster exhibit an enhancement in star formation compared to their field counterparts. This excess persists even without applying dust-attenuation corrections, indicating that enhanced star formation in the protocluster is robust regardless of whether a dust correction is applied. In contrast, intermediate- and high-mass PBEs ($M_\star > 10^9\,M_\odot$) show no significant deviation from the field, revealing a strong mass dependence in the environmental effects on star formation. No clear spatial concentration toward the cluster core of starbursting low-mass galaxies within the protocluster is seen, suggesting that their enhancement is not restricted to the cluster core. We suggest that starbursts in low-mass galaxies are facilitated by environmental processes such as galaxy mergers/interactions, and/or efficient gas supply. While the enhancement at the low-mass end is consistent with trends reported for other protoclusters at similar redshifts, the behaviour of star formation at intermediate masses ($10^{9} < M_\star/M_\odot < 10^{10}$) is not uniform across protoclusters. Our \pab-based results in the Spiderweb protocluster indicate that star-formation enhancement at cosmic noon depends on both mass and the dynamical state of the protocluster.

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arXiv2026

Chaotic Molecular Gas in Five Dusty Star-forming Galaxies in the Spiderweb Protocluster at $z = 2.16$

Measuring the properties of cold molecular gas available for intense star formation in galaxy protoclusters at $z>2$ is a crucial step in understanding large scale structure formation. We present ALMA observations of CO(3$-$2) in five dusty star-forming galaxies within $\sim0.5-4$ cMpc of the core of the Spiderweb protocluster at $z=2.16$ to measure the molecular gas mass and kinematics in the most starbursting members of the protocluster. All five galaxies exhibit evidence for disturbed kinematics including non-Gaussian CO line profiles, irregular spatial morphology, and strong residuals when fitting the galaxies with a classical disk model. This could be indicative of an elevated merger rate in the outskirts of the mature Spiderweb protocluster, as all of the galaxies in our sample have multiple companions detected in H$\alpha$. Both the gas fractions and the gas depletion timescales of the galaxies are similar to field relations at cosmic noon, indicative of the fact that their prodigious star formation rates are compensated by similarly high gas masses. The most massive galaxies, as well as all of the galaxies identified as X-ray AGN in previous works, have gas fractions $<30$%, compared to the sample average of 49%, indicating declining availability of gas for star formation. Finally, we find that the gas fractions and specific star formation rates decline with distance from the Spiderweb Galaxy, supporting the reversal of the SFR density--radius relation in high-redshift protoclusters.

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arXiv2025

Spider-Webb: Spatially-Resolved Evidence of Inside-Out Quenching in the Spiderweb Protocluster at $z \sim 2$

We present a spatially-resolved analysis of galaxy quenching within the Spiderweb Protocluster at $z \sim 2.16$, combining deep imaging from the James Webb Space Telescope (JWST) and the Hubble Space Telescope (HST). Utilizing pixel-by-pixel spectral energy distribution fitting, we derive maps of stellar mass, star formation rate (SFR), specific SFR (sSFR), and rest-frame UVJ colors. Quiescent galaxies, predominantly found at $\log(M_*/M_{\odot}) \geq 10.5$, exhibit clear mass-dependent inside-out quenching, with central sSFR approximately an order of magnitude lower than outer regions, while lower-mass star-forming galaxies show flat sSFR profiles. Central star formation activity fundamentally anti-correlates with S\'ersic index, indicating reduced activity in bulge-dominated systems. Spatially resolved UVJ colors reveal heterogeneous internal star formation, distinguishing star-forming regions in quiescent hosts from those in globally star-forming systems. These findings demonstrate that quenching mechanisms were effectively operating by $z \sim 2$, with the observed inside-out patterns and morphological correlations consistent with AGN-driven feedback processes. Our study provides key observational constraints on galaxy evolution during this critical epoch.

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arXiv2025

Why the Northern Hemisphere Needs a 30-40 m Telescope and the Science at Stake: Cosmology and High-z Universe

Full sky coverage with 30-40 meter-class telescopes is essential to answer fundamental questions in Astrophysics, Cosmology, and Physics, such as the composition of the Universe and the formation of the first stars and supermassive black holes. An ELT/TMT-like telescope in the Northern Hemisphere is a fundamental and necessary facility to provide multiplexing of observing power, diversity of instrumentation, rapid response, and statistical power required to address the questions and the problems, current and future, unveiled by full sky observatories such as JWST, Euclid, or Roman space telescopes. The Northern ELT/TMT will expedite the study of unique, extreme, rare, transient, and/or high-energy events which will give the most information about fundamental Physics problems in the era of multi-messenger and time-domain Astronomy.

astro-ph.IM↗

arXiv2025

The Photometric Analysis of the Environment Around Two Dusty Star-Forming Galaxies at $z \sim 2$

Studying the environments of dusty star-forming galaxies (DSFGs) provides insight into whether these luminous systems are reliable signposts of large-scale overdensities. Evidence suggests that individual DSFGs can trace overdense environments, although this association may not be universal. To test this, we investigate the environments surrounding two luminous, gravitationally-lensed DSFGs (SDP.17b at $z_\text{spec} = 2.3049$ and HELMS-55 at $z_\text{spec} = 2.2834$). Using Gemini South Flamingos-2 (F2) $K_s$-band imaging together with ancillary Subaru Hyper Suprime-Cam and Hubble Space Telescope multi-band photometry, we obtain photometric redshifts, $z_\text{phot}$, as well as star formation rates and stellar mass estimates for companion galaxies of the DSFGs. At least $5\pm2$ and $15\pm3$ companion galaxies exist with consistent $z_\text{phot}$ ($dz \leq 0.2$) within a projected separation of 5.5 cMpc of SDP.17b and HELMS-55, respectively. These correspond to galaxy overdensities of $\delta = 0.1 \pm 0.2$ and ${\delta} =1.0 \pm 0.3$, with significances of $(0.2 \pm 0.4)\sigma$ and $(2.2 \pm 0.6) \sigma$, respectively. On the $M_{\rm H_2}$-overdensity-significance plane, HELMS-55 may follow the positive correlation between the gas mass and the overdensity significance, while SDP.17b lies well above the relation despite its large gas reservoir, making it a potential outlier. Based on this study of two DSFGs, our photometric analysis suggests that DSFGs can trace the outskirts of protoclusters or associated large-scale structures. However, our small sample prevents firm conclusions about their ability to pinpoint dense cluster cores. Future multi-object spectroscopic observations are required to confirm the membership and star formation properties of the companion galaxies.

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arXiv2025

A MUltiwavelength Study of ELAN Environments (AMUSE$^2$): The Impact of Dense Environment on Massive Dusty Star-Forming Galaxies at Cosmic Noon

To understand how massive galaxies are influenced by their surroundings, we present new ALMA and NOEMA observations as part of A MUltiwavelength Study of ELAN Environments (AMUSE$^2$). These observations target submillimeter sources discovered in single-dish surveys around nine quasars hosting Ly$\alpha$ nebulae at $z=2\sim3$, including two Enormous Ly$\alpha$ nebulae (ELANe). Through detection of mid-$J$ CO lines, we confirm physical associations of 15 SMGs, which are located outside the expected virial radii of the central dark-matter halos hosting the quasars. We find $73^{+29}_{-21}\%$ of SMGs have line profiles better described by double Gaussian models, with a median peak-to-peak separation of 350 $\pm$ 25 km/s, suggesting rotating disks or interacting pairs. Modified blackbody fits of the far-infrared photometry yield a median $\beta$ of 2.0 $\pm$ 0.2 and $T_{dust}$ of 34 $\pm$ 3 K. Overall, SMGs outside quasar halos share similar physical properties with those in the field, but combining data from other studies reveals depleted gas fractions within quasar halos. This suggests that dense environments significantly impact massive star-forming galaxies only within halo scales at cosmic noon. Additionally, spatial analyses of 15 SMGs indicate they trace large-scale structures, possibly filamentary or elongated pancake-like, with a scale height of 2-5\,cMpc. Our measured distributions and densities of star-formation rates align with models, though likely represent lower limits.

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arXiv2025

NASIM: Revealing the low surface brightness Universe from legacy VISTA data

Near-infrared imaging is a powerful technique in observational astronomy, but the bright background, primarily from the Earth\'s atmosphere, makes the detection of faint features particularly challenging. To recover low surface brightness (LSB) structures in such data, we present NASIM (Near-infrared Automated low Surface brightness reduction In Maneage), a fully automated and reproducible data reduction pipeline optimised for VISTA/VIRCAM observations. NASIM builds on GNU Astronomy Utilities (Gnuastro) to effectively remove large-scale instrumental artefacts while preserving faint, diffuse emission. As a key science application, we focus on deep Ks-band observations of the Euclid Deep Field South (KEDFS), one of the deepest VISTA/VIRCAM datasets and a high-priority field for synergy with current and future facilities, including Euclid, JWST, LSST, Roman, Spitzer, and ALMA. With VIRCAM no longer operational, KEDFS now stands as a unique legacy dataset. We release selected tiles from the KEDFS survey and highlight science cases, including galaxy outskirts, LSB galaxies, and intracluster light, that demonstrate NASIM\'s ability to recover diffuse structures. A direct comparison with conventional VISTA data reduction pipelines demonstrates the advantages of NASIM in preserving diffuse emission without compromising compact source detection. All quantitative results presented in this paper are fully reproducible with Maneage (commit 4d32667).

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arXiv2024

Revealing the quiescent galaxy population in the Spiderweb protocluster at z=2.16 with deep HST/WFC3 slitless spectroscopy

We report the HST WFC3 G141 grism slitless spectroscopy observation of the core region of the Spiderweb protocluster at $z=2.16$. We analyzed the spectra of all objects in a $\sim 2 \times 2 \text{ arcmin}^2$ field of view and identified 40 protocluster members, recovering 19 previously identified H$\alpha$-emitters in addition to revealing 21 new members. The spectra allowed us to identify 11 galaxies with quiescent spectra. Three galaxies with quiescent spectra are possibly still star-forming according to SED fitting, indicating a possible left-over or dust-obscured star formation. We estimate a quiescent fraction of $\sim 50\%$ for $M_\star > 10^{11} M_\odot$. About half of the quiescent galaxies possibly host AGN, hinting at AGN's key role in quenching galaxies in the protocluster environment. These quiescent galaxies have relatively more compact and concentrated light profiles than the star-forming members, but they are not yet as bulge-dominated as local ellipticals. These results are consistent with previous studies that indicate the Spiderweb protocluster is in the maturing stage, with a red sequence that has begun forming.

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arXiv2024

Spider-Webb: JWST Near Infrared Camera resolved galaxy star formation and nuclear activities in the Spiderweb protocluster at z=2.16

Near-infrared (NIR) emission is less affected by dust than UV and optical emission and is therefore useful for studying the properties of dust-obscured galaxies. Although rest-frame NIR observations of high-redshift galaxies have long been made using space telescopes, their structures were unresolved due to the lack of angular resolution. This letter reports the early results from the analysis of high-resolution Pa$\beta$ imaging of the Spiderweb protocluster at $z=2.16$ with the JWST Near Infrared Camera. We investigate radial profiles of Pa$\beta$ lines and rest-frame NIR continua from luminous H$\alpha$-emitting galaxies (HAEs) in the protocluster. Particularly, we compare those of 11 HAEs (N-HAEs) on the star-forming main sequence with those of 8 HAEs (X-HAEs) with X-ray AGNs. Resultant composite Pa$\beta$ line images of N-HAEs indicate significant star formation in galactic disks. In contrast, X-HAEs are dominated by point source components rather than outer star formation, as inferred from our earlier work based on multi-wavelength SED fitting. Given their higher stellar potentials suggested from their rest-frame NIR images, the different characteristics may be driven by the impact of AGN feedback.

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arXiv2024

JWST/NIRCam Pa$\mathrm{\beta}$ narrow-band imaging reveals ordinary dust extinction for H$\mathrm{\alpha}$ emitters within the Spiderweb protocluster at z=2.16

We combine JWST/NIRCam and Subaru/MOIRCS dual Pa$\mathrm{\beta}$ + H$\mathrm{\alpha}$ narrow-band imaging to trace the dust attenuation and the star-formation activities of a sample of 43 H$\mathrm{\alpha}$ emitters at the core of one of the most massive and best-studied clusters in formation at the cosmic noon: the Spiderweb protocluster at $\mathrm{z=2.16}$. We find that most H$\mathrm{\alpha}$ emitters display Pa$\mathrm{\beta}$/H$\mathrm{\alpha}$ ratios compatible with Case B recombination conditions, which translates into nebular extinction values ranging at $\mathrm{A_V\approx0-3}$ magnitudes, and dust corrected $\mathrm{Pa\beta}$ star formation rates consistent with coeval main sequence field galaxies at fixed stellar mass ($\mathrm{9.4<\log M_*/M_\odot<11.0}$) during this cosmic epoch. Furthermore, we investigate possible environmental impacts on dust extinction across the protocluster large-scale structure and find no correlation between the dustiness of its members and environmental proxies such as phase-space position, clustercentric radius, or local density. These results support the scenario for which dust production within the main galaxy population of this protocluster is driven by secular star formation activities fueled by smooth gas accretion across its large-scale structure. This downplays the role of gravitational interactions in boosting star formation and dust production within the Spiderweb protocluster, in contrast with observations in higher redshift and less evolved protocluster cores.

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arXiv2024

JWST/NIRCam Narrowband Survey of Pa$\beta$ Emitters in the Spiderweb Protocluster at z=2.16

We report the initial result of our Pa$\beta$ narrowband imaging on a protocluster with the JWST Near Infrared Camera (NIRCam). As NIRCam enables deep narrowband imaging of rest-frame NIR lines at $z>1$, we target one of the most studied protoclusters, the Spiderweb protocluster at $z=2.16$, in which previous studies have confirmed more than a hundred member galaxies. The NIRCam F405N narrowband filter covers in Pa$\beta$ line the protocluster redshift given by known protocluster members, allowing the search for new member candidates. The weight-corrected color-magnitude diagram obtained 57 sources showing narrowband excesses, 41 of which satisfy further color selection criteria for limiting the sample to Pa$\beta$ emitter candidates at $z\sim2.16$, and 24 of them do not have H$\alpha$ emitter counterparts. The Pa$\beta$ emitter candidates appear to follow the spatial distribution of known protocluster members; however, follow-up spectroscopic confirmation is required. Only 17 out of 58 known H$\alpha$-emitting cluster members are selected as Pa$\beta$ emitters in the current data, albeit the rest fall out of the narrowband selection owing to their small Pa$\beta$ equivalent widths. We derive Pa$\beta$ luminosity function in the Spiderweb protocluster, showing a normalization density of $\log{\phi^\ast}=-2.53\pm0.15$ at a characteristic Pa$\beta$ luminosity of $\log{L^\ast}=42.33\pm0.17$. Furthermore, we examine the possibility of detecting faint line emitters visible only in the narrow-band image, but find no promising candidates.

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arXiv2024

The RAdio Galaxy Environment Reference Survey (RAGERS): Evidence of an anisotropic distribution of submillimeter galaxies in the 4C 23.56 protocluster at z=2.48

High-redshift radio(-loud) galaxies (H$z$RGs) are massive galaxies with powerful radio-loud active galactic nuclei (AGNs) and serve as beacons for protocluster identification. However, the interplay between H$z$RGs and the large-scale environment remains unclear. To understand the connection between H$z$RGs and the surrounding obscured star formation, we investigated the overdensity and spatial distribution of submillimeter-bright galaxies (SMGs) in the field of 4C\,23.56, a well-known H$z$RG at $z=2.48$. We used SCUBA-2 data ($\sigma\,{\sim}\,0.6$\,mJy) to estimate the $850\,{\rm \mu m}$ source number counts and examine the radial and azimuthal overdensities of the $850\,{\rm \mu m}$ sources in the vicinity of the H$z$RG. The angular distribution of SMGs is inhomogeneous around the H$z$RG 4C\,23.56, with fewer sources oriented along the radio jet. We also find a significant overdensity of bright SMGs (${\rm S}_{850\rm\,\mu m}\geq5\,$mJy). Faint and bright SMGs exhibit different spatial distributions. The former are concentrated in the core region, while the latter prefer the outskirts of the H$z$RG field. High-resolution observations show that the seven brightest SMGs in our sample are intrinsically bright, suggesting that the overdensity of bright SMGs is less likely due to the source multiplicity.

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arXiv2024

An ALMA survey of submillimetre galaxies in the Extended Chandra Deep Field South: an unbiased study of SMG environments measured with narrowband imaging

Submillimetre galaxies (SMGs) are some of the most extreme star-forming systems in the Universe, whose place in the framework of galaxy evolution is as yet uncertain. It has been hypothesised that SMGs are progenitors of local early-type galaxies, requiring that SMGs generally reside in galaxy cluster progenitors at high redshift. We test this hypothesis and explore SMG environments using a narrowband VLT/HAWK-I+GRAAL study of H$\alpha$ and [OIII] emitters around an unbiased sample of three ALMA-identified and spectroscopically-confirmed SMGs at $z \sim 2.3$ and $z \sim 3.3$, where these SMGs were selected solely on spectroscopic redshift. Comparing with blank-field observations at similar epochs, we find that one of the three SMGs lies in an overdensity of emission-line sources on the $\sim4$ Mpc scale of the HAWK-I field of view, with overdensity parameter $\delta_{g} = 2.6^{+1.4}_{-1.2}$. A second SMG is significantly overdense only on $\lesssim 1.6$ Mpc scales and the final SMG is consistent with residing in a blank field environment. The total masses of the two overdensities are estimated to be $\log(M_{h}/{\rm M}_{\odot}) =$12.1--14.4, leading to present-day masses of $\log(M_{h,z=0}/{\rm M}_{\odot}) =$12.9--15.9. These results imply that SMGs occupy a range of environments, from overdense protoclusters or protogroups to the blank field, suggesting that while some SMGs are strong candidates for the progenitors of massive elliptical galaxies in clusters, this may not be their only possible evolutionary pathway.

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arXiv2024

The Radio Galaxy Environment Reference Survey (RAGERS): a submillimetre study of the environments of massive radio-quiet galaxies at $z = 1{\rm -}3$

Measuring the environments of massive galaxies at high redshift is crucial to understanding galaxy evolution and the conditions that gave rise to the distribution of matter we see in the Universe today. While high-$z$ radio galaxies (H$z$RGs) and quasars tend to reside in protocluster-like systems, the environments of their radio-quiet counterparts are relatively unexplored, particularly in the submillimetre, which traces dust-obscured star formation. In this study we search for 850 $\mu$m-selected submillimetre galaxies in the environments of massive ($M_{\star} > 10^{11} M_{\odot}$), radio-quiet ($L_{500 {\rm MHz}} \lesssim 10^{25}$ W Hz$^{-1}$) galaxies at $z \sim 1\text{--}3$ using S2COSMOS data. By constructing number counts in circular regions of radius 1--6 arcmin and comparing with blank-field measurements, we find no significant overdensities of SMGs around massive radio-quiet galaxies at any of these scales, despite being sensitive down to overdensities of $\delta \sim 0.4$. To probe deeper than the catalogue we also examine the distribution of peaks in the SCUBA-2 SNR map, which reveals only tentative signs of any difference in the SMG densities of the radio-quiet galaxy environments compared to the blank field, and only on smaller scales (1$^{\prime}$ radii, corresponding to $\sim0.5$ Mpc) and higher SNR thresholds. We conclude that massive, radio-quiet galaxies at cosmic noon are typically in environments with $\delta\lesssim0.4$, which are either consistent with the blank field or contain only weak overdensities spanning sub-Mpc scales. The contrast between our results and studies of H$z$RGs with similar stellar masses and redshifts implies an intrinsic link between the wide-field environment and radio AGN luminosity at high redshift.

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arXiv2024

ALESS-JWST: Joint (sub-)kiloparsec JWST and ALMA imaging of $z\sim3$ submillimeter galaxies reveals heavily obscured bulge formation events

We present JWST NIRCam imaging targeting 13 $z\sim3$ infrared-luminous ($L_{\rm IR}\sim5\times10^{12}L_{\odot}$) galaxies from the ALESS survey with uniquely deep, high-resolution (0.08$''$$-$0.16$''$) ALMA 870$\mu$m imaging. The 2.0$-$4.4$\mu$m (observed frame) NIRCam imaging reveals the rest-frame near-infrared stellar emission in these submillimeter-selected galaxies (SMGs) at the same (sub-)kpc resolution as the 870$\mu$m dust continuum. The newly revealed stellar morphologies show striking similarities with the dust continuum morphologies at 870$\mu$m, with the centers and position angles agreeing for most sources, clearly illustrating that the spatial offsets reported previously between the 870$\mu$m and HST morphologies were due to strong differential dust obscuration. The F444W sizes are 78$\pm$21% larger than those measured at 870$\mu$m, in contrast to recent results from hydrodynamical simulations that predict larger 870$\mu$m sizes. We report evidence for significant dust obscuration in F444W for the highest-redshift sources, emphasizing the importance of longer-wavelength MIRI imaging. The majority of the sources show evidence that they are undergoing mergers/interactions, including tidal tails/plumes -- some of which are also detected at 870$\mu$m. We find a clear correlation between NIRCam colors and 870$\mu$m surface brightness on $\sim$1 kpc scales, indicating that the galaxies are primarily red due to dust -- not stellar age -- and we show that the dust structure on $\sim$kpc-scales is broadly similar to that in nearby galaxies. Finally, we find no strong stellar bars in the rest-frame near-infrared, suggesting the extended bar-like features seen at 870$\mu$m are highly obscured and/or gas-dominated structures that are likely early precursors to significant bulge growth.

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arXiv2024

A Comparative Study of the Ground State Transitions of CO and [C I] as Molecular Gas Tracers at High Redshift

The CO(1--0) and [\ion{C}{1}](1--0) emission lines are well-established tracers of cold molecular gas mass in local galaxies. At high redshift, where the interstellar medium (ISM) is likely to be denser, there have been limited direct comparisons of both ground state transitions. Here we present a study of CO(1--0) and [\ion{C}{1}](1--0) emission in a sample of 20 unlensed dusty, star-forming galaxies at $z=2-5$. The CO(1--0)/[\ion{C}{1}](1--0) ratio is constant up to at least $z=5$, supporting the use of [CI](1-0) as a gas mass tracer. PDR modelling of the available data indicates a median H$_2$ density of log$(n~[$cm$^{-3}])=4.7\pm0.2$, and UV radiation field log$(G_{\mathrm{UV}} [G$_0$])=3.2\pm0.2$. We use the CO(1--0), [\ion{C}{1}](1--0) and 3mm dust continuum measurements to cross--calibrate the respective gas mass conversion factors, finding no dependence of these factors on either redshift or infrared luminosity. Assuming a variable CO conversion factor then implies [\ion{C}{1}] and dust conversion factors that differ from canonically assumed values but are consistent with the solar/super-solar metallicities expected for our sources. Radiative transfer modelling shows that the warmer CMB at high redshift can significantly affect the [\ion{C}{1}] as well as CO emission, which can change the derived molecular gas masses by up to 70\% for the coldest kinetic gas temperatures expected. Nevertheless, we show that the magnitude of the effect on the ratio of the tracers is within the known scatter of the $L'_\mathrm{CO}-L'_\mathrm{[CI]}$ relation. Further determining the absolute decrease of individual line intensities will require well-sampled spectral line energy distributions (SLEDs) to model the gas excitation conditions in more detail.

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arXiv2024

Atacama Large Aperture Submillimeter Telescope (AtLAST) Science: Surveying the distant Universe

During the most active period of star formation in galaxies, which occurs in the redshift range 1<z<3, strong bursts of star formation result in significant quantities of dust, which obscures new stars being formed as their UV/optical light is absorbed and then re-emitted in the infrared, which redshifts into the mm/sub-mm bands for these early times. To get a complete picture of the high-z galaxy population, we need to survey a large patch of the sky in the sub-mm with sufficient angular resolution to resolve all galaxies, but we also need the depth to fully sample their cosmic evolution, and therefore obtain their redshifts using direct mm spectroscopy with a very wide frequency coverage. This requires a large single-dish sub-mm telescope with fast mapping speeds at high sensitivity and angular resolution, a large bandwidth with good spectral resolution and multiplex spectroscopic capabilities. The proposed 50-m Atacama Large Aperture Submillimeter Telescope (AtLAST) will deliver these specifications. We discuss how AtLAST allows us to study the whole population of high-z galaxies, including the dusty star-forming ones which can only be detected and studied in the sub-mm, and obtain a wealth of information for each of these up to z~7: gas content, cooling budget, star formation rate, dust mass, and dust temperature. We present worked examples of surveys that AtLAST can perform, both deep and wide, and also focused on galaxies in proto-clusters. In addition we show how such surveys with AtLAST can measure the growth rate and the Hubble constant with high accuracy, and demonstrate the power of the line-intensity mapping method in the mm/sub-mm wavebands to constrain the cosmic expansion history at high redshifts, as good examples of what can uniquely be done by AtLAST in this research field.

astro-ph.CO↗

arXiv2024

Atacama Large Aperture Submillimeter Telescope (AtLAST) Science: The hidden circumgalactic medium

Our knowledge of galaxy formation and evolution has incredibly progressed through multi-wavelength observational constraints of the interstellar medium (ISM) of galaxies at all cosmic epochs. However, little is known about the physical properties of the more diffuse and lower surface brightness reservoir of gas and dust that extends beyond ISM scales and fills dark matter haloes of galaxies up to their virial radii, the circumgalactic medium (CGM). New theoretical studies increasingly stress the relevance of the latter for understanding the feedback and feeding mechanisms that shape galaxies across cosmic times, whose cumulative effects leave clear imprints into the CGM. Recent studies are showing that a -- so far unconstrained -- fraction of the CGM mass may reside in the cold (T < 1e4 K) molecular and atomic phase, especially in high-redshift dense environments. These gas phases, together with the warmer ionised phase, can be studied in galaxies from z ~ 0 to z ~ 10 through bright far-infrared and sub-millimeter emission lines such as [C II] 158${\mu}$m, [O III] 88 ${\mu}$m, [C I] 609${\mu}$m, [C I] 370${\mu}$m, and the rotational transitions of CO. Imaging such hidden cold CGM can lead to a breakthrough in galaxy evolution studies but requires a new facility with the specifications of the proposed Atacama Large Aperture Submillimeter Telescope (AtLAST). In this paper, we use theoretical and empirical arguments to motivate future ambitious CGM observations with AtLAST and describe the technical requirements needed for the telescope and its instrumentation to perform such science.

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