Browsing by Author "Blana, Matias"

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    A MUSE view of the core of the giant low-surface-brightness galaxy Malin 1
    (2024) Johnston, Evelyn J.; Galaz, Gaspar; Blana, Matias; Amram, Philippe; Boissier, Samuel; Eigenthaler, Paul; Epinat, Benoit; Junais; Ordenes-Briceno, Yasna; Puzia, Thomas; Weilbacher, Peter M.
    Aims. The central region of the giant low-surface-brightness galaxy Malin 1 has long been known to have a complex morphology, with evidence of a bulge, disc, and potentially a bar hosting asymmetric star formation. In this work, we use VLT/MUSE data to resolve the central region of Malin 1 in order to determine its structure. Methods. We used careful light profile fitting in every image slice of the datacube to create wavelength-dependent models of each morphological component, from which we were able to cleanly extract their spectra. We then used the kinematics and emission line properties from these spectra to better understand the nature of each component extracted from our model fitting. Results. We report the detection of a pair of distinct sources at the centre of this galaxy with a separation of similar to 1.05 '', which corresponds to a separation on sky of similar to 1.9 kpc. The radial velocity data of each object confirm that they both lie in the kinematic core of the galaxy. An analysis of the emission lines reveals that the central compact source is more consistent with being ionised through star formation and/or a LINER, while the off-centre compact source lies closer to the separation between star-forming galaxies and active galactic nuclei. Conclusions. This evidence suggests that the centre of Malin 1 hosts either a bar with asymmetric star formation or two distinct components. In the latter scenario, we propose two hypotheses for the nature of the off-centre compact source-it could either be a star-forming clump, containing one or more star clusters, that is in the process of falling into the core of the galaxy and eventually merging with the central nuclear star cluster, or it could be a clump of gas falling into the centre of the galaxy from either outside or from the disc and triggering star formation there.
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    Bar-driven Gas Dynamics of M31
    (2024) Feng, Zi-Xuan; Li, Zhi; Shen, Juntai; Gerhard, Ortwin; Saglia, R. P.; Blana, Matias; Li, Hui; Jing, Yingjie
    The large-scale gaseous shocks in the bulge of M31 can be naturally explained by a rotating stellar bar. We use gas dynamical models to provide an independent measurement of the bar pattern speed in M31. The gravitational potentials of our simulations are from a set of made-to-measure models constrained by stellar photometry and kinematics. If the inclination of the gas disk is fixed at i = 77 degrees, we find that a low pattern speed of 16-20 km s-1 kpc-1 is needed to match the observed position and amplitude of the shock features, as shock positions are too close to the bar major axis in high omega b models. The pattern speed can increase to 20-30 km s-1 kpc-1 if the inner gas disk has a slightly smaller inclination angle compared with the outer one. Including subgrid physics such as star formation and stellar feedback has minor effects on the shock amplitude, and does not change the shock position significantly. If the inner gas disk is allowed to follow a varying inclination similar to the H i and ionized gas observations, the gas models with a pattern speed of 38 km s-1 kpc-1, which is consistent with stellar-dynamical models, can match both the shock features and the central gas features.
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    First Detection of Molecular Gas in the Giant Low Surface Brightness Galaxy Malin 1
    (2024) Galaz, Gaspar; Gonzalez-Lopez, Jorge; Guzman, Viviana; Messias, Hugo; Junais, Samuel; Boissier, Samuel; Epinat, Benoit; Weilbacher, Peter M.; Puzia, Thomas; Johnston, Evelyn J.; Amram, Philippe; Frayer, David; Blana, Matias; Howk, J. Christopher; Berg, Michelle; Bustos-Espinoza, Roy; Munoz-Mateos, Juan Carlos; Cortes, Paulo; Garcia-Appadoo, Diego; Joachimi, Katerine
    After over three decades of unsuccessful attempts, we report the first detection of molecular gas emission in Malin 1, the largest spiral galaxy observed to date, and one of the most iconic giant low surface brightness galaxies. Using Atacama Large Millimeter/submillimeter Array, we detect significant 12CO (J = 1-0) emission in the galaxy's central region and tentatively identify CO emission across three regions on the disk. These observations allow for a better estimate of the H2 mass and molecular gas mass surface density, both of which are remarkably low given the galaxy's scale. By integrating data on its H i mass, we derive a very low molecular-to-atomic gas mass ratio. Overall, our results highlight the minimal presence of molecular gas in Malin 1, contrasting sharply with its extensive, homogeneous atomic gas reservoir. For the first time, we position Malin 1 on the Kennicutt-Schmidt diagram, where it falls below the main sequence for normal spirals, consistent with previous upper limits but now with more accurate figures. These findings are crucial for constraining our understanding of star formation processes in environments characterized by extremely low molecular gas densities and for refining models of galaxy formation, thereby improving predictions concerning the formation, evolution, and distribution of these giant, elusive galaxies.
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    Large-scale Hydrodynamical Shocks as the Smoking-gun Evidence for a Bar in M31
    (2022) Feng, Zi-Xuan; Li, Zhi; Shen, Juntai; Gerhard, Ortwin; Saglia, R. P.; Blana, Matias
    The formation and evolutionary history of M31 are closely related to its dynamical structures, which remain unclear due to its high inclination. Gas kinematics could provide crucial evidence for the existence of a rotating bar in M31. Using the position-velocity diagram of [O III] and H I, we are able to identify clear sharp velocity jump (shock) features with a typical amplitude over 100 km s(-1) in the central region of M31 (4.6 kpc x 2.3 kpc, or 20' x 10'). We also simulate gas morphology and kinematics in barred M31 potentials and find that the bar-induced shocks can produce velocity jumps similar to those in [O III]. The identified shock features in both [O III] and H I are broadly consistent, and they are found mainly on the leading sides of the bar/bulge, following a hallmark pattern expected from the bar-driven gas inflow. Shock features on the far side of the disk are clearer than those on the near side, possibly due to limited data coverage on the near side, as well as to obscuration by the warped gas and dust layers. Further hydrodynamical simulations with more sophisticated physics are desired to fully understand the observed gas features and to better constrain the parameters of the bar in M31.