arXiv subjects

Mark D. Gorski

Publications and source records attributed to Mark D. Gorski.

6 recordsLinked to original sources

arXiv2026

Modeling the Milky Way Circumnuclear Disk: Rosettes and Rings

The Milky Way Galactic Center hosts a $\sim4\times10^{6}\,M_\odot$ supermassive black hole (SMBH), Sagittarius A* (Sgr A*). The dominant structures in its immediate vicinity are the nuclear star cluster (NSC), whose enclosed mass at 2 pc is approximately half that of the SMBH, and the circumnuclear disk (CND)/ring, which extends between $\sim0.5$ pc and $\sim3$ pc from Sgr A* and is the largest reservoir of molecular gas in this region. Existing models of the CND commonly use one circular orbit to describe the motion of its gas. Here, we explore a much broader range of models. In the combined potential of Sgr A* and the NSC, we consider non-Keplerian rosette orbits as well as a circular disk, which is formed using a finely spaced set of concentric rings. For both systems, we test various inner/outer radii, inclinations, and position angles, sampling a total of $\sim3.3 \times 10^{5}$ models. We then conduct mock observations of all models to construct velocity maps, which we compare with HCN ($J=1{-}0$) observations of the CND. We find that the best-fitting model is a circular disk with inner and outer radii of 1.0 pc and 2.9 pc, an inclination of $i=60^{\circ}$, and a position angle of $\text{PA} = 35^{\circ}.$

astro-ph.GA↗

arXiv2026

ALMA Central molecular zone Exploration Survey (ACES) VI: ALMA Large Program Reveals a Highly Filamentary Central Molecular Zone

The Central Molecular Zone (CMZ) of the Milky Way is the way station that primarily controls how much gas flows from the disk of the Galaxy towards the central nucleus. While this region is well documented to have extreme gas properties that clearly distinguish it from the rest of the Galaxy, the properties of the bulk molecular gas at high angular resolution are relatively unexplored. Band 3 data from the ALMA (Atacama Large Millimeter/Submillimeter Array) large program ACES (ALMA CMZ Exploration Survey) reveal the highly filamentary nature of CMZ molecular gas at high resolution (3" or 0.1pc) across the entire CMZ. Visual inspection of these data suggests that there are at least two general classes of elongated structures, which we identify as: i) large-scale (10 pc) filamentary structures (LFs) and ii) a ubiquitous population of small-scale (about 1 pc) filamentary structures (SFs). We present detailed morphological and kinematic properties towards three structures in each category, as well as their association with magnetic fields and the correlation of HNCO 4(0,4)-3(0,3) with other molecular species. Our investigation reveals that these structures are largely coherent in position-position-velocity space. The alignment with the magnetic field structure is mixed, with some parallel, some perpendicular, and some intermediate alignments. We find that LFs likely trace pieces of contiguous CMZ orbital structures and are a manifestation of global CMZ dynamics. The second class, SFs, are pervasive and may be the result of complicated turbulence and shearing dynamics in the CMZ gas flows, as seen in numerical simulations.

astro-ph.GA↗

arXiv2026

The Discovery of an Active Wind from the Milky Way's Black Hole

Every large galaxy has a black hole in its center. The interaction between the black hole and its host profoundly shapes galactic evolution and the Universe as a whole. The key features of this interaction are black hole jets -- or more generally, winds -- which every black hole must have. Despite the proximity and importance of our Galaxy's central black hole, Sagittarius A* (Sgr A*), the active wind from it has eluded scientists for over half a century. Here we report the discovery of a large active wind from Sgr A* using unprecedentedly deep (T$_b \sim30$ mK) and high angular resolution (<0.25") observations with the Atacama Large Millimeter/Submillimeter Array (ALMA). We detect a large conical clearing in the cold molecular gas surrounding Sgr A* that is at least 1~parsec long and has a ~45 degree opening angle. The morphology and energetics of this structure are consistent with active clearing of gas by a hot wind from Sgr A*.

astro-ph.GA↗

arXiv2025

The Dust Polarisation and Magnetic Field Structure in the Centre of NGC253 with ALMA

Magnetic fields have an impact on galaxy evolution at multiple scales. They are particularly important for starburst galaxies, where they play a crucial role in shaping the interstellar medium (ISM), influencing star formation processes and interacting with galactic outflows. The primary aim of this study is to obtain a parsec scale map of dust polarisation and B-field structure within the central starburst region of NGC253. This includes examining the relationship between the morphology of B-fields, galactic outflows and the spatial distribution of super star clusters (SSC), to understand their combined effects on the galaxy's star formation and ISM. We used ALMA full polarisation data in Bands 4 (145 GHz) and 7 (345 GHz) with resolution of 25 and 5 pc scale, respectively. According to our SED fitting analysis, the observed Band 4 emission is a combination of dust, synchrotron and free-free, while Band 7 traces only dust. The polarisation fraction (PF) of the synchrotron component is 2%, while that of the dust component is 0.3%. The B-fields orientation maps in both bands at common resolution show that the same B-fields structure is traced by dust and synchrotron emission at scales of 25 pc. The B-field morphology suggests a coupling with the multiphase outflow, while the distribution of PF in Band 7 showed to be correlated with the presence of SSC. We observed a significant anti-correlation between polarisation fraction and column density in both Bands 4 and 7. A negative correlation between PF and dispersion angle function was observed in Band 4 but was nearly absent in Band 7 at native resolution, suggesting that the tangling of B-field geometry along the plane of the sky is the main cause of depolarisation at 25 pc scales, while other factors play a role at 5 pc scales.

astro-ph.GA↗

arXiv2024

The ALCHEMI atlas: principal component analysis reveals starburst evolution in NGC 253

Molecular lines are powerful diagnostics of the physical and chemical properties of the interstellar medium (ISM). These ISM properties, which affect future star formation, are expected to differ in starburst galaxies from those of more quiescent galaxies. We investigate the ISM properties in the central molecular zone of the nearby starburst galaxy NGC 253 using the ultra-wide millimeter spectral scan survey from the ALMA Large Program ALCHEMI. We present an atlas of velocity-integrated images at a 1".6 resolution of 148 unblended transitions from 44 species, including the first extragalactic detection of HCNH$^+$ and the first interferometric images of C$_3$H$^+$, NO, HCS$^+$. We conduct a principal component analysis (PCA) on these images to extract correlated chemical species and to identify key groups of diagnostic transitions. To the best of our knowledge, our dataset is currently the largest astronomical set of molecular lines to which PCA has been applied. The PCA can categorize transitions coming from different physical components in NGC 253 such as i) young starburst tracers characterized by high-excitation transitions of HC$_3$N and complex organic molecules (COMs) versus tracers of on-going star formation (radio recombination lines) and high-excitation transitions of CCH and CN tracing PDRs, ii) tracers of cloud-collision-induced shocks (low-excitation transitions of CH$_3$OH, HNCO, HOCO$^+$, and OCS) versus shocks from star-formation-induced outflows (high-excitation transitions of SiO), as well as iii) outflows showing emission from HOC$^+$, CCH, H$_3$O$^+$, CO isotopologues, HCN, HCO$^+$, CS, and CN. Our findings show these intensities vary with galactic dynamics, star formation activities, and stellar feedback.

astro-ph.GA↗

arXiv2020

Evidence for Coupling of Evolved Star Atmospheres and Spiral Arms of the Milky Way

It is imperative to map the strength and distribution of feedback in galaxies to understand how feedback affects the galactic ecosystems. H$_2$O masers act as indicators of energy injection into the ISM. Our goal is to measure the strength and distribution of feedback traced by water masers in the Milky Way. We identify optical counterparts to H$_2$O masers discovered by the HOPS survey. The distribution and luminosities of H$_2$O masers in the Milky Way are determined using parallax measurements derived from the second Gaia Data Release. We provide evidence of a correlation between evolved stars, as traced by H$_2$O masers, and the spiral structure of the Milky Way, suggesting a link between evolved stars and the Galactic environment.

astro-ph.GA↗