bendixh

• Liu, Daizhong; Saintonge, Amelie; Bot, Caroline; Kemper, Francisca; Lopez-Rodriguez, Enrique & Smith, Matthew [Vis alle 28 forfattere av denne artikkelen] (2025). Atacama Large Aperture Submillimeter Telescope (AtLAST) science: Gas and dust in nearby galaxies. Open Research Europe. 4. doi: 10.12688/openreseurope.17459.2. Fulltekst i vitenarkiv Vis sammendrag

  Understanding the physical processes that regulate star formation and galaxy evolution are major areas of activity in modern astrophysics. Nearby galaxies offer unique opportunities to inspect interstellar medium (ISM), star formation (SF), radiative, dynamic and magnetic ( B → ) physics in great detail from sub-galactic (kpc) scales to sub-cloud (sub-pc) scales, from quiescent galaxies to starbursts, and from field galaxies to overdensities. In this case study, we discuss the major breakthroughs in this area of research that will be enabled by the Atacama Large Aperture Submillimeter Telescope (AtLAST), a proposed 50-m single-dish submillimeter telescope. The new discovery space of AtLAST comes from its exceptional sensitivity, in particular to extended low surface brightness emission, a very large 2° field of view, and correspondingly high mapping efficiency. This paper focuses on four themes which will particularly benefit from AtLAST: 1) the LMC and SMC, 2) extragalactic magnetic fields, 3) the physics and chemistry of the interstellar medium, and 4) star formation and galaxy evolution. With ~ 1000 − 2000 hour surveys each, AtLAST could deliver deep dust continuum maps of the entire LMC and SMC fields at parsec-scale resolution, high-resolution maps of the magnetic field structure, gas density, temperature and composition of the dense and diffuse ISM in ~ 100 nearby galaxies, as well as the first large-scale blind CO survey in the nearby Universe, delivering molecular gas masses for up to 10 6 galaxies (3 orders of magnitude more than current samples). Through such observing campaigns, AtLAST will have a profound impact on our understanding of the baryon cycle and star formation across a wide range of environments.

• Hagedorn, Jan Bendix; Cicone, Claudia; Sarzi, M.; Saintonge, A.; Severgnini, P. & Vignali, C. [Vis alle 10 forfattere av denne artikkelen] (2024). Molecular gas scaling relations for local star-forming galaxies in the low-M* regime. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 687. doi: 10.1051/0004-6361/202449773. Fulltekst i vitenarkiv Vis sammendrag

  We derived molecular gas fractions (fmol = Mmol/M*) and depletion times (τmol = Mmol/SFR) for 353 galaxies representative of the local star-forming population with 108.5 M⊙ < M* < 1010.5 M⊙ drawn from the ALLSMOG and xCOLDGASS surveys of CO(2−1) and CO(1−0) line emission. By adding constraints from low-mass galaxies and upper limits for CO non-detections, we find the median molecular gas fraction of the local star-forming population to be constant at log fmol = −0.99−0.19+0.22, challenging previous reports of increased molecular gas fractions in low-mass galaxies. Above M* ∼ 1010.5 M⊙, we find the fmol versus M* relation to be sensitive to the selection criteria for star-forming galaxies. We tested the robustness of our results against different prescriptions for the CO-to-H2 conversion factor and different selection criteria for star-forming galaxies. The depletion timescale τmol weakly depends on M*, following a power law with a best-fit slope of 0.16 ± 0.03. This suggests that small variations in specific star formation rate (sSFR = SFR/M*) across the local main sequence of star-forming galaxies with M* < 1010.5 M⊙ are mainly driven by differences in the efficiency of converting the available molecular gas into stars. We tested these results against a possible dependence of fmol and τmol on the surrounding (group) environment of the targets by splitting them into centrals, satellites, and isolated galaxies, and find no significant variation between these populations. We conclude that the group environment is unlikely to have a large systematic effect on the molecular gas content of star-forming galaxies in the local Universe.

• Arroyave, Isabel Montoya; Cicone, Claudia; Andreani, P.; Weiss, A.; Breuck, C De & Lundgren, A. [Vis alle 11 forfattere av denne artikkelen] (2024). A possible relation between global CO excitation and massive molecular outflows in local ULIRGs. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 686. doi: 10.1051/0004-6361/202348292. Fulltekst i vitenarkiv Vis sammendrag

  Local ultra-luminous infrared galaxies (ULIRGs) have been observed to host ubiquitous molecular outflows, including the most massive and powerful ever detected. These sources have also exceptionally excited global, galaxy-integrated CO ladders. A connection between outflows and molecular gas excitation has however never been established, since previous multi-J CO surveys were limited in spectral resolution and sensitivity and so they could only probe the global molecular gas conditions. In this work, we address this question using new, ground-based, sensitive heterodyne spectroscopy of multiple CO rotational lines (up to CO(7−6)) in a sample of 17 local ULIRGs. We used the Atacama Pathfinder Experiment (APEX) telescope to survey the CO(Jup ≥ 4) lines at a high signal-to-noise ratio, and complemented these data with CO(Jup ≤ 3) APEX and Atacama Large Millimeter Array (ALMA and ACA) observations presented in Montoya Arroyave et al. (2023, A&A, 673, A13). We detected a total of 74 (out of 75) CO lines, with up to six transitions per source. The resulting CO spectral line energy distributions (SLEDs) show a wide range in gas excitation, in agreement with previous studies on ULIRGs. Some CO SLEDs peak at Jup ∼ 3, 4, which we classify as “lower excitation”, while others plateau or keep increasing up to the highest-J CO transition probed, and we classify these as “higher excitation”. Our analysis includes for completeness the results of CO SLED fits performed with a single large velocity gradient component, but our main focus is the investigation of possible links between global CO excitation and the presence of broad and/or high-velocity CO spectral components that can contain outflowing gas. We discovered an increasing trend of line width as a function of Jup of the CO transition, which is significant at the 4σ level and appears to be driven by the eight sources that we classified as higher excitation. We further analyzed such higher-excitation ULIRGs, by performing a decomposition of their CO spectral profiles into multiple components, and we derived CO ladders that are clearly more excited for the spectral components characterized by higher velocities and/or velocity dispersion. Because these sources are known to host widespread molecular outflows, we favor an interpretation whereby the highly excited CO-emitting gas in ULIRGs resides in galactic-scale massive molecular outflows whose emission fills a large fraction of the beam of our APEX high-J CO observations. On the other hand, our results challenge alternative scenarios for which the high CO excitation in ULIRGs can be explained by classical component of the interstellar medium, such as photon- or X-ray dominated regions around the nuclear sources.

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• Hagedorn, Jan Bendix (2026). A multiphase investigation of the baryon cycle in local galaxies. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  In this thesis, I investigated interstellar gas in nearby galaxies. The life cycle of this gas is known as the baryon cycle. As interstellar gas cools down, it forms dense clouds that eventually collapse into stars. This dense molecular gas is of great interest to observers studying star formation and galaxy evolution. I studied the cold molecular gas in a large sample of local low-mass galaxies, to understand how their gas content scales with their mass and rate of star formation. The results showed that small galaxies in the local universe on average contain similar amounts of cold gas than their larger counterparts, but that they are slightly more efficient at turning it into stars. The formation of stars and the growth of supermassive black holes release enormous amounts of energy, which can eject gas from the galaxy in the form of outflows. I searched for outflows in low-mass galaxies, finding that with sufficient spectral resolution, they are found very commonly in this population. Finally, I studied an outflow in a massive galaxy merger measuring tracers of molecular, atomic, and ionized gas that appears to be accelerated out to several kiloparsecs. I use a new technique to measure the mass of the molecular gas and dust in the outflow.

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