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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., Comment: 47 pages, 12 figures. For further details on AtLAST see https://atlast.uio.no

NGC 5128 (Cen A) is the nearest giant elliptical galaxy and one of the brightest extragalactic radio sources in the sky, boasting a prominent dust lane and jets emanating from its nuclear supermassive black hole. In this paper, we construct the star formation history (SFH) of two small fields in the halo of NGC 5128: a northeastern field (Field 1) at a projected distance of $\sim 18.8$ kpc from the center, and a southern field (Field 2) $\sim 9.9$ kpc from the center. Our method is based on identifying long period variable (LPV) stars that trace their sibling stellar population and hence historical star formation due to their high luminosity and strong variability; we identified 395 LPVs in Field 1 and 671 LPVs in Field 2. Even though the two fields are $\sim 28$ kpc apart on opposite sides from the center, they show similar SFHs. In Field 1, star formation rates (SFRs) increased significantly around $t\sim 800$ Myr and $t\sim 3.8$ Gyr; and in Field 2, SFRs increased considerably around $t\sim 800$ Myr, $t\sim 3.8$ Gyr, and $t\sim 6.3$ Gyr, where $t$ is look--back time. The increase in SFR $\sim 800$ Myr ago agrees with previous suggestions that the galaxy experienced a merger around that time. The SFH reconstructed from LPVs supports a scenario in which multiple episodes of nuclear activity lead to episodic jet-induced star formation. While there is no catalog of LPVs for the central part of NGC 5128, applying our method to the outer regions (for the first time in a galaxy outside the Local Group) has enabled us to put constraints on the complex evolution of this cornerstone galaxy., Comment: Accepted for publication in ApJ

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, simultaneously 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., Comment: 14 pages, 4 figures, submitted to Open Research Europe as part of a collection on the Atacama Large Aperture Submillimeter Telescope (AtLAST)

We present a photometric study of the resolved stellar populations in And IX, the closest satellite to the M31, a metal-poor and low-mass dwarf spheroidal galaxy. We estimate a distance modulus of $24.56_{-0.15}^{+0.05}$ mag based on the tip of the red giant branch (TRGB). By probing the variability of asymptotic giant branch stars (AGB), we study the star formation history of And IX. We identified 50 long period variables (LPVs) in And IX using the Isaac Newton Telescope (INT) in two filters, Sloan $i'$ and Harris $V$. In this study, we selected LPVs within two half-light radii with amplitudes in the range of 0.2-2.20 mag. It is found that the peak of star formation reaches $\sim$ $8.2\pm3.1\times10^{-4}$ M_sun yr$^{-1}$ at $\approx 6$ Gyr ago. Our findings suggest an outside-in galaxy formation scenario for And IX with a quenching occurring $3.65_{-1.52}^{+0.13}$ Gyr ago with the SFR in the order of $2.0\times10^{-4}$ M_sun yr$^{-1}$ at redshift < $0.5$. We calculate the total stellar mass by integrating the star formation rate (SFR) within two half-light radii $\sim$ $3.0\times10^5$ M_sun. By employing the spectral energy distribution (SED) fitting for observed LPVs in And IX, we evaluate the mass-loss rate in the range of $10^{-7}$ $\leq$ $\dot{M}$ $\leq$ $10^{-5}$ M_sun yr$^{-1}$. Finally, we show that the total mass deposition to the interstellar medium (ISM) is $\sim$ $2.4\times10^{-4}$ M_sun yr$^{-1}$ from the C- and O-rich type of dust-enshrouded LPVs. The ratio of the total mass returned to the ISM by LPVs to the total stellar mass is $\sim 8.0\times10^{-10}$ yr$^{-1}$, and so at this rate, it would take $\sim$ 1 Gyr to reproduce this galaxy, Comment: Accepted for publication in ApJ

Local Group (LG), the nearest and most complete galactic environment, provides valuable information on the formation and evolution of the Universe. Studying galaxies of different sizes, morphologies, and ages can provide this information. For this purpose, we chose the And\,IX dSph galaxy, which is one of the observational targets of the Isaac Newton Telescope (INT) survey. A total of 50 long-period variables (LPVs) were found in And\,IX in two filters, Sloan $i'$ and Harris $V$ at a half-light radius of 2.5 arcmin. The And\,IX's star formation history (SFH) was constructed with a maximum star formation rate (SFR) of about $0.00082\pm0.00031$ M$_\odot$ yr$^{-1}$, using LPVs as a tracer. The total mass return rate of LPVs was calculated based on the spectral energy distribution (SED) of about $2.4\times10^{-4}$ M$_\odot$ yr$^{-1}$. The distance modulus of $24.56_{-0.15}^{+0.05}$ mag was estimated based on the tip of the red giant branch (TRGB)., Comment: Proceedings of IAUS373 "Resolving the Rise and Fall of Star Formation in Galaxies", August 2 - 11, 2022

We conducted an optical monitoring survey of the Sagittarius dwarf irregular galaxy (SagDIG) during the period of June 2016 -- October 2017, using the 2.5-m Isaac Newton Telescope (INT) at La Palama. Our goal was to identify Long Period Variable stars (LPVs), namely asymptotic giant branch stars (AGBs) and red supergiant stars (RSGs), to obtain the Star Formation History (SFH) of isolated, metal-poor SagDIG. For our purpose, we used a method that relies on evaluating the relation between luminosity and the birth mass of these most evolved stars. We found $27$ LPV candidates within two half-light radii of SagDIG. $10$ LPV candidates were in common with previous studies, including one very dusty AGB (x-AGB). By adopting the metallicity $Z = 0.0002$ for older population and $Z=0.0004$ for younger ages, we estimated that the star formation rate changes from $0.0005\pm0.0002$ M$_{\odot}$yr$^{-1}$kpc$^{-2}$ ($13$ Gyr ago) to $0.0021 \pm 0.0010$ M$_{\odot}$yr$^{-1}$kpc$^{-2}$ ($0.06$ Gyr ago). Like many dwarf irregular galaxies, SagDIG has had continuous star formation activity across its lifetime, though with different rates, and experiences an enhancement of star formation since $z \simeq 1$. We also evaluated the total stellar mass within two half-light radii of SagDIG for three choices of metallicities. For metallicity $Z = 0.0002$ and $Z=0.0004$ we estimated the stellar mass M$_*$ = ($5.4 \pm 2.3$) $\times$ $10^ 6$ and ($3.0 \pm 1.3$) $\times$ $10^ 6$ M$_{\odot}$, respectively. Additionally, we determined a distance modulus $\mu$ = $25.27\pm0.05$ mag, using the tip of the red giant branch (TRGB)., Comment: 16 pages, Accepted for publication in ApJ

NGC5128 galaxy is a giant elliptical galaxy located in the Centaurus group of galaxies at 3.8 Mpc. We aim to study the star formation history (SFH) of two different fields of the galaxy. The northeastern field (Field 1) is located at a distance of 18.8 kpc, while the southern field (Field 2) is at 9.9 kpc. We use a photometric method that is based on identifying long period variable (LPV) stars and asymptotic giant branch (AGB) stars, as they are strong tracers of star formation and galaxy evolution due to their luminosity and variability; 395 LPVs in Field 1 and 671 LPVs in Field 2 have been identified. These two fields present similar SFHs, although the SF rate of Field 2 is more enhanced. We find that the galaxy has three major star formation episodes t $\sim$ 800 Myr ago, t $\sim$ 3.2 Gyr ago, and t $\sim$ 10 Gyr ago, where t is look-back time. The rate of star formation at $\sim$ 800 Myr ago agrees with previous studies suggesting that the galaxy experienced a merger around that time. Furthermore, NGC5128 has experienced a lower star formation rate in its recent history which could have been driven by jet-induction star formation and multiple outbursts of AGN activity in this galaxy, as well as a minor merger around 400 Myr ago., Comment: 4 pages, 1 figure, Proceeding Paper of IAU Symposium 373

An activity indicator, which can provide a robust quantitative mapping between the stellar activity and the physical properties of its atmosphere, is important in exploring the physics of activity across spectral types. But the common activity indicators show large variability in their values which makes defining a robust quantitative scale difficult. Millimetre (mm) wavelengths probe the different atmospheric layers within the stellar chromosphere providing a tomographic view of the atmospheric dynamics. The project aims to define a robust mm-based activity indicator for the cool main-sequence stars ($\mathrm{T_{eff}} \sim$ 5000 - 7000 K). We derive the mm-brightness temperature ($\mathrm{T_B(\nu)}$) spectral indices ($\mathrm{\alpha_{mm}}$) for cool stars including the Sun using archival data in the 30 - 1000 GHz range. The derived values for $\mathrm{\alpha_{mm}}$ are explored as a function of various physical parameters and empirical power-law functions were derived. $\mathrm{\alpha_{mm}}$ estimates were also compared with other activity indicators. Despite the estimation errors, $\mathrm{\alpha_{mm}}$ values could well distinguish the cool stars, unlike common activity indicators. The low estimation errors on the derived trends of $\mathrm{\alpha_{mm}}$ versus physical parameters suggest that $\mathrm{\alpha_{mm}}$ could be a robust activity indicator. $\mathrm{\alpha_{mm}}$, which is linked to chromospheric thermal stratification and activity in cool stars can well distinguish and physically characterise the stars more robustly than common activity indicators. We emphasise the need for multi-frequency data across the mm-band for stars, with a range of physical parameters and gathered at multiple epochs during activity cycles. This will help explore $\mathrm{\alpha_{mm}}$ in a statistically robust manner and study the emergence of chromospheric heating on the main-sequence., Comment: Accepted in A&A Letters

The cosmic origin of fluorine is still under debate. Asymptotic giant branch (AGB) stars are among the few suggested candidates to efficiently synthesis F in our Galaxy, however their relative contribution is not clear. In this paper, we briefly review the theoretical studies from stellar yield models of the F synthesis and chemical equilibrium models of the F-containing molecules in the outflow around AGB stars. Previous detections of the F-bearing species towards AGB and post-AGB stars are also highlighted. We suggest that high-resolution ALMA observations of the AlF, one of the two main carriers of F in the outflow of AGB stars, can provide a reliable tracer of the F-budget in AGB stars. This will be helpful to quantify the role of AGB stars in the Galactic F budget.

Due to their wide wavelength coverage across the millimetre to centimetre (mm - cm) range and their increased sensitivity, modern interferometric arrays facilitate observations of the thermal and non-thermal emission from different stellar atmospheric layers. We study the spectral energy distribution ($S_{obs}(\nu)$) of main sequence stars using archival mm - cm data with the aim to study their atmospheric stratification as a function of stellar type. The main-sequence stars with significant detection in mm bands were identified in the ALMA Science Archive. These data were complemented with spectral flux data in the Ultra violet to centimetre range as compiled from various catalogues and observatory archives. We compare the resultant $S_{obs}(\nu)$ of each star with a photospheric emission model ($S_{mod}(\nu)$) calculated with the PHOENIX code. The departures of $S_{obs}(\nu)$ from the model are quantified in terms of a "spectral flux excess" parameter ($\Delta S/S_{mod} (\nu)$) for every star in the sample. The initial sample consists of 12 stars across a range of spectral type from A1 to M3.5 and the Sun-as-a-star as reference. The stars with $T_{eff} = 4000 - 7000\,K$ (F - M type) showed a systematically higher $\Delta S/S_{mod}$ in the mm - cm range, with the values rising with decreasing $\nu$. The steepness of this rise is higher for cooler stars, though the fully convective 3000 K star in the sample deviated from this trend. For the A-type stars, $\Delta S/S_{mod} \sim 0$ within errors. The high $\Delta S/S_{mod}$ in cool stars points to the presence of hotter upper atmospheric layers, i.e. a chromosphere and corona, like for the Sun. The mm - cm $\Delta S/S_{mod}$ spectrum offers a way to estimate the efficiency of the heating mechanisms across various atmospheric layers and thereby to understand their structure and activity. We emphasise the need for more mm - cm data., Comment: Accepted for publication in A&A

Carbon monoxide (CO) is the most abundant molecule after molecular hydrogen and is important for the chemistry in circumstellar envelopes around evolved stars. When modelling the strength and shape of molecular lines, the size of the CO envelope is an input parameter and influences the derived mass-loss rates. In particular the low-J transition CO lines are sensitive to the CO photodissociation radius. Recently, new CO photodissociation radii have been published using different formalisms that differ considerably. One set of calculations is based on an escape-probability formalisms that uses numerical approximations derived in the early-eighties. The accuracy of these approximations is investigated and it is shown that they are less accurate than claimed. Improved formalism are derived. Nevertheless, the changes in CO envelope size are small to moderate, less than 2\% for models with $10^{-7}< \dot{M}< 10^{-4}$ \msolyr\ and at most 7\% for model with $\dot{M} = 10^{-8}$ \msolyr., Comment: A&A, accepted for publication

Ultraviolet (UV) photodissociation of CO controls the abundances and distribution of CO and its photodissociation products. This significantly influences the gas-phase chemistry in the circumstellar envelope (CSE) around evolved stars. A better understanding of CO photodissociation in outflows also provides a more precise estimate of mass-loss rates. We aim to update the CO photodissociation rate in an expanding spherical envelope assuming that the interstellar radiation field (ISRF) photons penetrate through the envelope. This will allow us to precisely estimate the CO abundance distributions in CSEs around evolved stars. We used the most recent CO spectroscopic data to precisely calculate the depth dependency of the photodissociation rate of each CO dissociating line. We calculated the CO self- and mutual-shielding functions in an expanding envelope. We investigated the dependence of the CO profile on the five fundamental parameters mass-loss rate, the expansion velocity, the CO initial abundance, the CO excitation temperature, and the strength of the ISRF. Our derived CO envelope size is smaller than the commonly used radius derived by Mamon et al. 1988. The difference between results varies from 1% to 39% and depends on the H2 and CO densities of the envelope. We list two fitting parameters for a large grid of models to estimate the CO abundance distribution. We demonstrate that the CO envelope size can differ between outflows with the same effective content of CO, but different CO abundance, mass-loss rate, and the expansion velocity as a consequence of differing amounts of shielding by H2 and CO. We find that the abundance of CO close to the star and the outflow density both can have a significant effect on the size of the molecular envelope. We also demonstrate that modest variations in the ISRF can cause measurable differences in the envelope extent.

We have conducted a near-infrared monitoring campaign at the UK InfraRed Telescope (UKIRT), of the Local Group spiral galaxy M33 (Triangulum). The main aim was to identify stars in the very final stage of their evolution, and for which the luminosity is more directly related to the birth mass than the more numerous less-evolved giant stars that continue to increase in luminosity. In this fourth paper of the series, we present a search for variable red giant stars in an almost square degree region comprising most of the galaxy's disc, carried out with the WFCAM instrument in the K band. These data, taken during the period 2005--2007, were complemented by J- and H-band images. Photometry was obtained for 403 734 stars in this region; of these, 4643 stars were found to be variable, most of which are Asymptotic Giant Branch (AGB) stars. The variable stars are concentrated towards the centre of M33, more so than low-mass, less-evolved red giants. Our data were matched to optical catalogues of variable stars and carbon stars and to mid-infrared photometry from the Spitzer Space Telescope. Most dusty AGB stars had not been previously identified in optical variability surveys, and our survey is also more complete for these types of stars than the Spitzer survey. The photometric catalogue is made publicly available at the Centre de Donnees astronomiques de Strasbourg., Comment: Accepted for publication in MNRAS

We present a new high signal to noise ratio spectroscopic survey of the Northern hemisphere to probe the Local Bubble and its surroundings using the $\lambda 5780$ \AA\ and $\lambda 5797$ \AA\ Diffuse Interstellar Bands (DIBs). We observed 432 sightlines to a distance of 200 pc over a duration of 3 years. In this study, we establish the $\lambda 5780$ and $\lambda 5797$ correlations with Na I, Ca II and E(B-V), for both inside and outside the Local Bubble. The correlations show that among all neutral and ionized atoms, the correlation between Ca II and $\lambda5780$ is stronger than its correlation with $\lambda5797$, suggesting that $\lambda5780$ is more associated with regions where Ca$^{+}$ is more abundant. We study the $\lambda5780$ correlation with $\lambda5797$, which shows a tight correlation within and outside the Local Bubble. In addition we investigate the DIB properties in UV irradiated and UV shielded regions. We find that, within and beyond the Local Bubble, $\lambda5797$ is located in denser parts of clouds, protected from UV irradiation, while $\lambda5780$ is located in the low density regions of clouds.

Human culture is uniquely cumulative and open-ended. Using a computational model of cultural evolution in which neural network based agents evolve ideas for actions through invention and imitation, we tested the hypothesis that this is due to the capacity for recursive recall. We compared runs in which agents were limited to single-step actions to runs in which they used recursive recall to chain simple actions into complex ones. Chaining resulted in higher cultural diversity, open-ended generation of novelty, and no ceiling on the mean fitness of actions. Both chaining and no-chaining runs exhibited convergence on optimal actions, but without chaining this set was static while with chaining it was ever-changing. Chaining increased the ability to capitalize on the capacity for learning. These findings show that the recursive recall hypothesis provides a computationally plausible explanation of why humans alone have evolved the cultural means to transform this planet., Comment: 8 pages. arXiv admin note: text overlap with arXiv:1308.5032, arXiv:1005.1516, arXiv:1309.7407, arXiv:0911.2390, arXiv:0811.2551, arXiv:1310.0522