arXiv subjects

Pamela Klaassen

Publications and source records attributed to Pamela Klaassen.

At least 19 recordsLinked to original sources

arXiv2026

IPA: Morphology and Kinematics of Molecular Hydrogen Winds in Five Young Protostars across the Mass Spectrum Observed with JWST

Molecular winds may play a key role in governing angular momentum transport and accretion during the early evolution of protostars. We present the morphology and kinematic properties of the H$_2$ emission in five young, envelope-dominated, protostars across a broad bolometric luminosity range, from 0.2 to $10^4~L_{\odot}$, observed with the NIRSpec/IFU and MIRI/MRS onboard JWST as part of the Investigating Protostellar Accretion (IPA) program. A rich set of pure rotational lines of H$_2$, up to $v=0-0$ S(18), and a few ro-vibrational lines are detected in the winds, revealing bipolar structures. The H$_2$ lines show a stratified/onion-like structure morphologically and kinematically, where the lines with higher $E_{\rm up}$ show a higher degree of collimation and higher velocities. Additionally, the wind velocity scales with the $L_{\rm bol}$ of the host protostellar system. In 4 out of 5 protostars, H$_2$ emission fills the outflow cavity without showing pronounced limb brightening. We also report a tentative detection of H$_2$ wind rotation in IRAS 16253, which suggests a launch radius of $\sim4$ au and the magnetic lever arm parameter of $\sim5-10$. Taken together, these properties of the H$_2$ winds can be explained by the magnetohydrodynamic disk wind models. We detect a collimated, high-velocity H$_2$ jet toward HOPS 370, which is more evolved than the extremely young source HH 211, but is accreting at a high accretion rate. This suggests that the presence of collimated molecular jets in protostars is more closely connected to accretion rate than system age.

astro-ph.SR↗

arXiv2026

The Atacama Large Aperture Submillimeter Telescope (AtLAST): enabling large-scale sub-mm science beyond 2030

AtLAST is designed to be the largest (sub-)mm single-dish astronomical observatory and the first climate-neutral modern research infrastructure. It offers a unique combination of large aperture (50 m), large field of view (>1 deg), fast scanning speed (up to 3 deg/s), and high surface accuracy (20micron nighttime half wavefront error) that allows >=50% Ruze efficiency up to 1 THz. The design features a rocking chair mount with an active main reflector surface, a high precision closed-loop metrology system, and the space to house six major instruments. Instruments will be periodically updated as spectroscopic focal plane array, detector, coherent amplifier, and semiconductor technologies used in readout and backend electronics will advance over the next decades. AtLAST will be a multi-purpose facility that will produce transformational results in nearly all fields of Astrophysics, such as Astrochemistry, Galactic and Extragalactic Astronomy, Cosmology, Planetary science, Stellar and Solar Physics, High energy astrophysics, and Time domain astronomy. Its unrivalled throughput of 6170 m^2 deg^2 will enable wide-field unbiased surveys. These will overcome extragalactic confusion noise and enable the detection of normal galaxy populations out to z=7. AtLAST will reveal and characterise the missing baryons in the Universe, by mapping the elusive, low surface brightness gas within and around galaxies across cosmic time. AtLAST will be the first green off-grid observatory, powered by a bespoke renewable energy system and reusing its braking energy thanks to a cutting-edge energy recovery system. By sharing surplus power and technological know-how with local communities, AtLAST will contribute to energy justice in Chile. AtLAST's new bold vision of a sustainable pursuit of breakthrough astronomy is an exceptional opportunity to shape the future of scientific research infrastructures. [abridged]

astro-ph.IM↗

arXiv2026

Unveiling Complex Chemistry in Planet-forming Disks with the SKAO

The chemical composition of planets is inherited from that of the natal protoplanetary disk at the time of planet formation. In recent years, we have made huge progress in characterizing disk chemistry. (Sub-)millimeter interferometers, such as ALMA, allowed us to detect emission lines from simple to complex organic molecules and to probe their radial and vertical distribution in disks. On the other hand, JWST has started to unveil the composition of disk ices, and line emission from the innermost disk regions. The advent of SKA will open new domains in the field, by observing emission lines from heavier molecules including heavy carbon chains and rings, and prebiotic molecules with peak emission in the cm range. Moreover, SKA will probe molecular emission from regions which are obscured by dust opacity at mm wavelengths, hence from the disk midplane, and often from the inner 30 au region. These observations will constrain the initial conditions for disk evolution and planet formation, allowing us to predict the chemical composition of the forming planets and their atmospheres. Comparison with forthcoming results on exoplanet atmospheres and on the chemistry of pristine bodies in the Solar System will provide new hints on the origin and evolution of planetary systems including our own.

astro-ph.SR↗

arXiv2026

JOYS: Launching and destruction of dust in protostellar jets. The case of BHR71-IRS1 with JWST/MIRI

Protostellar winds can theoretically lift solids from the planet-forming disks, but direct evidence for launched dust has been scarce so far. Numerous atomic lines that are unique to mid-infrared (IR) wavelengths reveal refractories eroded from dust grains and provide information on wind properties in the earliest stages of the star formation process. We present JWST/MIRI-MRS spectral imaging of the inner 2000 au of the BHR71-IRS1 blueshifted side of the outflow. Atomic line intensities are compared to shock models to constrain the physical conditions and elemental abundances of the outflowing gas. Dust continuum maps are constructed from PSF-subtracted cubes, and the dust spectral energy distribution is analyzed. The ionized central jet of BHR71-IRS1 is spatially resolved and imaged for the first time, revealing a unique inventory of refractory, volatile, and noble-gas fine-structure lines (Fe, Ni, Co, Cl, S, Ne, Ar). The emission is concentrated along four bright knots that wiggle along the jet axis. PSF-subtracted continuum maps reveal extended mid-IR continuum emission co-spatial with the jet bullets and within the H$_2$-traced outflow cone. Spectral energy distributions along the jet are fit together with the extinction, revealing a warm (200-400 K) and a cold (70-90 K) dust component. Shock modeling constrained by the mid-IR lines indicates a decline in shock velocity from 70 to 35 km s$^{-1}$ and pre-shock density from $>$10$^5$ to $ 4\times 10^4$ cm$^{-3}$ with distance from the protostar. Gas-phase Fe and Ni are measurably depleted relative to Solar abundances, consistent with a substantial fraction of refractories remaining locked in grains in spite of the shocks. These JWST observations provide direct evidence that dust is launched in a Class 0 jet and at least partly survives shock processing.

astro-ph.SR↗

arXiv2026

ALMAGAL VII. Cataloging Hierarchical Mass Structure from Cores to Clumps across the Galactic Disk

Investigating the multi-scale fragmentation of dense clumps into compact cores is essential for understanding the processes that govern the initial distribution of mass in stellar clusters and how high-mass stars ($>8~M_{\odot}$) form. We present a catalog of the hierarchical continuum structure from 904 clumps observed in the ALMAGAL program, a high resolution ($0.15-0.8$\arcsec) 1.38 mm Atacama Large Millimeter/submillimeter Array (ALMA) large program targeting dense clumps capable of high-mass star formation throughout the Galactic disk. We use \verb|astrodendro|, a dendrogram-based algorithm, on a uniform linear resolution (2000 au) version of the data to extract 5160 continuum structures with effective radii spanning $800-42000$ au and estimated masses between $~0.05-670~M_{\odot}$. With our large sample, we statistically examine differences in clump properties for regions with varying levels of hierarchical complexity. We find that clumps exhibiting the richest hierarchical morphology have distributions with higher dust temperatures, surface densities, luminosity-to-mass (\textit{L/M}) ratios, and most massive core (MMC) masses, indicating that these regions tend to be at later evolutionary stages. We find a positive correlation between the mass of cores from the ALMAGAL core catalog and the surface density of their surrounding structures identified in this work. However, this correlation is weaker for cores in more evolved clumps, where lower mass cores can be found at higher local surface densities. This could indicate that some cores accrete mass less efficiently from the intra-clump reservoir than others, despite the total available mass increasing over time, a scenario that is congruent with a clump-fed core accretion model.

astro-ph.GA↗

arXiv2026

Investigating the Nested Structure of the Outflow from the Low Luminosity Protostar IRAS 16253-2429 using JWST and ALMA

Understanding the earliest stage of star and planet formation requires detailed observations to address the connection and interplay between the accretion, outflow and disk evolution. We present results from the observations of the low luminosity ($L_\mathrm{bol}\sim~0.2~L_\odot$) and mass (M$_*\sim$\,0.15~M$_\odot$) Class~0 protostar IRAS 16253$-$2429, conducted as part of the \textit{eDisk} ALMA large program and the JWST cycle-1 GO program \textit{IPA}. Observations reveal a wide hourglass-shaped continuum cavity traced in scattered light (at $\leq$~5~$μ$m), with a brighter, extended northern side. We detect 15 pure rotational H$_2$ transitions (E$_\mathrm{up}$:~1015--21411~K), revealing a wide-angle molecular outflow. {The outflow width (as traced in H$_2$~0-0~S(11)) at the protostellar location measures $\leq$35 au, slightly larger than the dust and Keplerian disk diameters ($\sim$30 au) but wider than the 20--23~au jet width in [Fe II].} {The opening angle narrows from 40--35\arcdeg{} for the low-J H$_2$ lines (up to S(5)) and the cold gas component (ALMA $^{12}$CO) to $\sim$28--19\arcdeg{} for the high-J H$_2$ lines (S(7)--S(11)).} Position-velocity diagrams of H$_2$ reveal higher velocities for higher E$_{up}$, ranging from ~12.5 km~s$^{-1}$ for H$_2$~0-0~S(1) and S(2) to ~28.5 km~s$^{-1}$ for H$_2$~0-0~S(5)~and~S(7) with respect to the mean flow velocity. The nested excitation and velocity structure of the collimated jet and wide angle wind suggest a magnetohydrodynamic wind as a likely launching mechanism, similar to the findings in other protostars and Class II sources. The lower velocity mm CO may be gas from the infalling envelope accelerated outwards by the wide angle wind along the cavity walls.

astro-ph.SR↗

arXiv2026

Gravitational trapping and ram pressure trapping of ultracompact and hypercompact H II regions

Observationally, early H II regions are classified by size into ultracompact and hypercompact configurations. It remains unclear whether these phases are long-lived or transient. Understanding the physical processes that stall H II region growth may help to solve the so-called lifetime problem: the observation of more compact H II regions than expected from theory. Utilizing two-dimensional, axially symmetric radiation hydrodynamic simulations of young expanding H II regions, including the phase of early star and disk formation, we seek to better understand the trapping of H II regions. Trapping forces include gravity and ram pressure, which oppose forces such as thermal pressure expansion, radiation pressure, and centrifugal force. Without radiation pressure, the H II region remains gravitationally trapped in the ultracompact phase indefinitely. With radiation pressure, the H II region escapes gravitational trapping but experiences ram pressure trapping on larger scales. For initial mass reservoirs with high central density, no trapping occurs, while a less steep density gradient yields clear trapped phases. Hypercompact trapped phases exhibit a so-called flickering variation in H II region radius, in agreement with observations of stalling and even contraction over small time scales. With radiation pressure, low-density reservoirs experience both gravitational and ram pressure trapping, while high-mass reservoirs undergo only the latter.

astro-ph.SR↗

arXiv2026

The Structure and Kinematics of Three Class 0 Protostellar Jets from JWST

We present observations of jets within 2000 au of three deeply embedded protostars using 2.9-27 micron observations with JWST. These observations show the morphologies and kinematics of the collimated jets from three protostars, the low-mass Class 0 protostars B335 and HOPS 153, and the intermediate-mass protostar HOPS 370. These jets are traced by shock-ionized fine-structure line emission observed with the JWST NIRSpec and MIRI IFUs. We find that [Fe II] emission traces the full extent of the inner 1000 to 2000 au of the jets, depending on distance to the protostar, while other ions mostly trace isolated shocked knots. The jets show evidence of wiggling motion in the plane of the sky as well as asymmetries between blue and red-shifted lobes. The widths of the jets increase non-monotonically with distance from the central protostar, with opening angles ranging from 2.1 degrees to < 10.1 degrees for the three protostars in the sample. The jets have total velocities ranging from 147 to 184 km/s after correcting for disk inclination. For B335, an 8-month gap between NIRSpec and MIRI MRS observations enabled measurement of the tangential velocity of a shocked knot; in combination with the radial velocity, this shows that the jet has a different inclination than the outflow cavity. We find multiple knots before and during a recent outburst in B335, although the knots were more frequent during the burst. The asymmetries between blue- and red-shifted lobes strongly suggest complex interactions between the circumstellar disks and magnetic fields.

astro-ph.SR↗

arXiv2025

IPA. Accretion rate of a low-mass Class 0 protostar, measured via mid-infrared fluorescent OH emission

The earliest stages of star formation are highlighted by complex interactions between accretion, outflow, and radiative processes, which shape the chemical and physical environment of the emerging protostar. James Webb Space Telescope observations of the low-mass, low-luminosity Class 0 protostar IRAS 16253-2429 reveal a central compact source. This object exhibits a rich mid-infrared emission spectrum of OH pure rotational lines and $\rm CO_2$ ro-vibrational lines. Unusually for a young stellar object, it has no mid-infrared line emission from $\rm H_2O$ to match the other molecules. We demonstrate that the emitting OH molecules arise from UV photodissociation of $\rm H_2O$ in its second absorption band at $λ= 114-145$ nm, and that the OH emission is a fluorescent cascade starting with highest-excitation rotational states. This situation offers the opportunity of using the infrared OH spectrum to measure the UV flux from the central protostar. Thereby we determine the disk-star accretion rate to be $3 \times 10^{-10} \ M_\sun \ {\rm year^{-1}}$, and demonstrate that the system luminosity arises mostly from the protostar's photosphere rather than from accretion luminosity. The result is in accord with the measured outflow rate of IRAS 16253-2429 and lies within the outflow/accretion-flow rate trend often inferred for protostars; and with episodic accretion as the dominant mechanism by which this protostar has grown.

astro-ph.SR↗

arXiv2025

Mass Assembly and Chemical Complexity in the Milky Way

(Sub-)millimeter spectral lines can be used not only to understand the chemical complexity and enrichment history of an observed portion of our Galaxy, but with spectrally resolved lines, they reveal the physical conditions, dynamics, and even the ionisation state and magnetic field strengths of the gas component of our Galaxy. They are prime tracers of mass assembly and structure formation across scales.

astro-ph.GA↗

arXiv2025

Non-detection of J1407b in ALMA Band 7 Observations

We report on ALMA Band 7 continuum observations towards the star 1SWASP J140747.93-394542.6 taken in mid 2024. These observations were a follow-up of a previous detection of an emission source in the J1407 field of view at an unexpected position in 2017. Proper motion analysis indicated that if this were the object responsible for the 2007 eclipse of J1407, it would be detectable at a new position, but still within an ALMA field of view in 2024. Here we present the non-detection of emission in the ALMA field of view (to a 1σ upper limit of 17.5 μJy),at both the 2017 position, and the position expected from proper motions. We place upper limits on a source at the proper motion corrected expected location in this 2024 data, and rule out the possibility of a dusty object being responsible for the 2007 eclipse

astro-ph.GA↗

arXiv2025

Atacama Large Aperture Submillimeter Telescope (AtLAST) Science: Resolving the Hot and Ionized Universe through the Sunyaev-Zeldovich effect

An omnipresent feature of the multi-phase ``cosmic web'' is that warm/hot (>$10^5$ K) ionized gas pervades it. This gas constitutes a relevant contribution to the overall universal matter budget across multiple scales, from the several tens of Mpc-scale IGM filaments, to the Mpc ICM, all the way down to the CGM surrounding individual galaxies from ~1 kpc up to their respective virial radii (~100 kpc). The study of the hot baryonic component of cosmic matter density represents a powerful means for constraining the intertwined evolution of galactic populations and large-scale cosmological structures, for tracing the matter assembly in the Universe and its thermal history. To this end, the SZ effect provides the ideal observational tool for measurements out to the beginnings of structure formation. The SZ effect is caused by the scattering of the photons from the cosmic microwave background off the hot electrons embedded within cosmic structures, and provides a redshift-independent perspective on the thermal and kinematic properties of the warm/hot gas. Still, current and future (sub)mm facilities have been providing only a partial view of the SZ Universe due to any combination of: limited angular resolution, spectral coverage, field of view, spatial dynamic range, sensitivity. In this paper, we motivate the development of a wide-field, broad-band, multi-chroic continuum instrument for the Atacama Large Aperture Submillimeter Telescope (AtLAST) by identifying the scientific drivers that will deepen our understanding of the complex thermal evolution of cosmic structures. On a technical side, this will necessarily require efficient multi-wavelength mapping of the SZ signal with an unprecedented spatial dynamic range (from arcsecond to tens of arcminutes) and we employ theoretical forecasts to determine the key instrumental constraints for achieving our goals. [abridged]

astro-ph.CO↗

arXiv2025

HDO ice detected toward an isolated low-mass protostar with JWST

Water is detected in environments representing every stage of star and solar system formation, but its chemical evolution throughout these stages remains poorly constrained. Deuterium ratios offer a means of probing chemical links between water in different cosmic regions because of their sensitivity to physicochemical conditions. Here, we present the first detection of the 4.1 $μ$m HDO ice feature with JWST toward a low-mass protostar, L1527 IRS, which may eventually grow to a sun-like mass. We measure an ice HDO/H$_{2}$O ratio of 4.4$^{+3.7}_{-1.7}$$\times$10$^{-3}$, where the reported error is dominated by uncertainties in continuum definition and ice band strengths. This fraction is similar to the gas HDO/H$_{2}$O ratios measured in the warm ($>$100 K) inner cores of other low-mass protostellar envelopes and protoplanetary disks found in comparably isolated star-forming regions. Such a similarity tentatively supports the assumption that water vapor detected in these regions is not significantly altered by gas-phase reactions following ice sublimation. It also supports the hypothesis that pre- and protostellar water ice is largely inherited in a chemically unaltered state by outer protoplanetary disks. However, the fraction is a factor of $\sim$4-10 times higher than the gas HDO/H$_{2}$O ratios measured toward comets and low-mass protostars in clustered star-forming regions. This difference may be due to either gas-phase water reprocessing in protostellar envelopes and protoplanetary disks, or differences between prestellar conditions of isolated dense cores and the clustered star-forming regions that are more analogous to the environment in which our Sun formed.

astro-ph.SR↗

arXiv2025

The conceptual design of the 50-meter Atacama Large Aperture Submillimeter Telescope (AtLAST)

The (sub)millimeter sky contains a vast wealth of information that is both complementary and inaccessible to other wavelengths. Over half the light we receive is observable at (sub)millimeter wavelengths, yet we have mapped only a small portion of the sky at sufficient spatial resolution and sensitivity to detect and resolve distant galaxies or star forming cores within their large-scale environments. For decades the astronomical community has highlighted the need for a large, high-throughput (sub-)mm ($λ\sim 0.35-10$ mm) single dish. The Atacama Large Aperture Submillimeter Telescope (AtLAST), with its 50-m aperture and $2^\circ$ maximal field of view, aims to be such a facility. We present here the preliminary design concept for AtLAST, developed through an EU Horizon 2020-funded design study. Our design approach begins with a long lineage of (sub)millimeter telescopes, relies on calculations and simulations to realize the optics, and uses finite element analysis to optimize the designs for the mechanical structure and subsystems. The demanding technical requirements for AtLAST, set by transformative science goals, have motivated the design effort to combine novel concepts with lessons learned from the past experience of previous efforts. The result is an innovative rocking chair design with six instrument bays, two of which are mounted on Nasmyth platforms, inside a large receiver cabin. Ultimately, AtLAST aims to achieve a surface accuracy of $\leq 20~μ$m root mean square half wavefront error, corresponding a Ruze efficiency $>50\%$ at 950~GHz. We conclude that closed-loop metrology of the active primary surface will likely be required to achieve our surface accuracy goal. In the next phase of the project, we will prototype and test such metrology on existing platforms, with a goal of delivering a mature, construction-ready design by the end of this decade.

astro-ph.IM↗

arXiv2024

Atacama Large Aperture Submillimeter Telescope (AtLAST) Science: Solar and stellar observations

Observations at (sub-)millimeter wavelengths offer a complementary perspective on our Sun and other stars, offering significant insights into both the thermal and magnetic composition of their chromospheres. Despite the fundamental progress in (sub-)millimeter observations of the Sun, some important aspects require diagnostic capabilities that are not offered by existing observatories. In particular, simultaneous observations of the radiation continuum across an extended frequency range would facilitate the mapping of different layers and thus ultimately the 3D structure of the solar atmosphere. Mapping large regions on the Sun or even the whole solar disk at a very high temporal cadence would be crucial for systematically detecting and following the temporal evolution of flares, while synoptic observations, i.e., daily maps, over periods of years would provide an unprecedented view of the solar activity cycle in this wavelength regime. As our Sun is a fundamental reference for studying the atmospheres of active main sequence stars, observing the Sun and other stars with the same instrument would unlock the enormous diagnostic potential for understanding stellar activity and its impact on exoplanets. The Atacama Large Aperture Submillimeter Telescope (AtLAST), a single-dish telescope with 50\,m aperture proposed to be built in the Atacama desert in Chile, would be able to provide these observational capabilities. Equipped with a large number of detector elements for probing the radiation continuum across a wide frequency range, AtLAST would address a wide range of scientific topics including the thermal structure and heating of the solar chromosphere, flares and prominences, and the solar activity cycle. In this white paper, the key science cases and their technical requirements for AtLAST are discussed.

astro-ph.SR↗

arXiv2024

JWST-IPA: Chemical Inventory and Spatial Mapping of Ices in the Protostar HOPS370 -- Evidence for an Opacity Hole and Thermal Processing of Ices

The composition of protoplanetary disks, and hence the initial conditions of planet formation, may be strongly influenced by the infall and thermal processing of material during the protostellar phase. Composition of dust and ice in protostellar envelopes, shaped by energetic processes driven by the protostar, serves as the fundamental building material for planets and complex organic molecules. As part of the JWST GO program, "Investigating Protostellar Accretion" (IPA), we observed an intermediate-mass protostar HOPS 370 (OMC2-FIR3) using NIRSpec/IFU and MIRI/MRS. This study presents the gas and ice phase chemical inventory revealed with the JWST in the spectral range of $\sim$2.9 to 28 $μ$m and explores the spatial variation of volatile ice species in the protostellar envelope. We find evidence for thermal processing of ice species throughout the inner envelope. We present the first high-spatial resolution ($\sim 80$ au) maps of key volatile ice species H$_{2}$O, CO$_{2}$, $^{13}$CO$_2$, CO, and OCN$^-$, which reveal a highly structured and inhomogeneous density distribution of the protostellar envelope, with a deficiency of ice column density that coincides with the jet/outflow shocked knots. Further, we observe high relative crystallinity of H$_{2}$O ice around the shocked knot seen in the H$_2$ and OH wind/outflow, which can be explained by a lack of outer colder material in the envelope along the line of sight due to the irregular structure of the envelope. These observations show clear evidence of thermal processing of the ices in the inner envelope, close to the outflow cavity walls, heated by the luminous protostar.

astro-ph.SR↗

arXiv2024

IPA: Class 0 Protostars Viewed in CO Emission Using JWST

We investigate the bright CO fundamental emission in the central regions of five protostars in their primary mass assembly phase using new observations from JWST's Near-Infrared Spectrograph (NIRSpec) and Mid-Infrared Instrument (MIRI). CO line emission images and fluxes are extracted for a forest of $\sim$150 ro-vibrational transitions from two vibrational bands, $v=1-0$ and $v=2-1$. However, ${}^{13}$CO is undetected, indicating that ${}^{12}$CO emission is optically thin. We use H$_2$ emission lines to correct fluxes for extinction and then construct rotation diagrams for the CO lines with the highest spectral resolution and sensitivity to estimate rotational temperatures and numbers of CO molecules. Two distinct rotational temperature components are required for $v=1$ ($\sim600$ to 1000 K and 2000 to $\sim 10^4$ K), while one hotter component is required for $v=2$ ($\gtrsim 3500$ K). ${}^{13}$CO is depleted compared to the abundances found in the ISM, indicating selective UV photodissociation of ${}^{13}$CO; therefore, UV radiative pumping may explain the higher rotational temperatures in $v=2$. The average vibrational temperature is $\sim 1000$ K for our sources and is similar to the lowest rotational temperature components. Using the measured rotational and vibrational temperatures to infer a total number of CO molecules, we find that the total gas masses range from lower limits of $\sim10^{22}$ g for the lowest mass protostars to $\sim 10^{26}$ g for the highest mass protostars. Our gas mass lower limits are compatible with those in more evolved systems, which suggest the lowest rotational temperature component comes from the inner disk, scattered into our line of sight, but we also cannot exclude the contribution to the CO emission from disk winds for higher mass targets.

astro-ph.SR↗

arXiv2024

AtLAST Science Overview Report

Submillimeter and millimeter wavelengths provide a unique view of the Universe, from the gas and dust that fills and surrounds galaxies to the chromosphere of our own Sun. Current single-dish facilities have presented a tantalising view of the brightest (sub-)mm sources, and interferometers have provided the exquisite resolution necessary to analyse the details in small fields, but there are still many open questions that cannot be answered with current facilities. In this report we summarise the science that is guiding the design of the Atacama Large Aperture Submillimeter Telescope (AtLAST). We demonstrate how tranformational advances in topics including star formation in high redshift galaxies, the diffuse circumgalactic medium, Galactic ecology, cometary compositions and solar flares motivate the need for a 50m, single-dish telescope with a 1-2 degree field of view and a new generation of highly multiplexed continuum and spectral cameras. AtLAST will have the resolution to drastically lower the confusion limit compared to current single-dish facilities, whilst also being able to rapidly map large areas of the sky and detect extended, diffuse structures. Its high sensitivity and large field of view will open up the field of submillimeter transient science by increasing the probability of serendipitous detections. Finally, the science cases listed here motivate the need for a highly flexible operations model capable of short observations of individual targets, large surveys, monitoring programmes, target of opportunity observations and coordinated observations with other observatories. AtLAST aims to be a sustainable, upgradeable, multipurpose facility that will deliver orders of magnitude increases in sensitivity and mapping speeds over current and planned submillimeter observatories.

astro-ph.IM↗