Resumen:

Entender la relación entre los procesos de formación estelar y el medio interestelar (ISM) es un paso clave para discernir la complejidad en la historia de evolución de las galaxias. Un problema en este aspecto ha sido entender la naturaleza e importancia de los procesos de retroalimentación (feedback) en los cuales estrellas masivas depositan energía en el medio interestelar a través de fotoionización, vientos estelares y supernovas. Este mecanismo de feedback afecta el estado físico y dinámico del ISM y por lo tanto tiene influencia en la tasa y distribución de formación estelar de las galaxias. En este contexto, la existencia de una componente templada e ionizada del ISM que se distribuye de manera omnipresente en los discos de galaxias ha sido conocida por décadas, tanto en nuestra Galaxia como en fuentes extragalácticas . A esta componente se le denomina gas ionizado difuso (DIG). En este trabajo definimos una muestra de 265 galaxias observadas con el instrumento MUSE IFS del telescopio VLT-8.1m para realizar un estudio espectral y análisis espacial del DIG, para explorar las distribuciones de las especies de baja ionización [OIII], [OI], [NII] y [SII] en los regímenes DIG a lo largo de los planos galácticos, así como discernir los diferentes mecanismos de ionización que resultan en este gas. Creamos una metodología basada en la creación de mapas de líneas de emisión a partir de los cubos de datos MUSE después de realizar una síntesis de poblaciones estelares a cada spaxel. También elaboramos un método de binning adaptativo para aumentar la relación señal-ruido de las líneas más débiles, como [OIII], [OI] y [SII]. Probamos esta metodología utilizando una submuestra de la muestra BETIS que consiste en 7 galaxias diferentes.

Resumen:

Since the discovery, five years ago, of large amplitude light variations, the high-mass Class I young stellar object (HMYSO) Mol 12 (IRAS05373+2349) has been observed extensively. The object is at a distance of 1.6 kpc, reddened by at least Av =15, and has a total luminosity of around two thousand Lo. It drives a bipolar outflow, which excites a number shocked knots of molecular hydrogen emission. Mol 12 exhibits variations of more than 6 magnitudes in the J band (1.25 microns) that suggest a series of eclipses by dust structures Results and analyses of the detailed monitoring of the capricious behaviour of Mol12 from the red to mid-infrared wavelengths will be presented. The new data includes detailed light curves, as well as medium-resolution spectroscopy. The effects of the protoplanetary disc dominates the emission in this range. The physical conditions and evolutionary status will be discussed.

Resumen:

The ALMA-IMF Large Program mapped 15 dense, massive ($2-32\times 10^{3}$~M$_{\odot}$), and ``typical" Milky Way protoclusters down at matched physical resolution of 2~kAU. Here we present N$_2$H$^+$ dense gas kinematic analysis of the G353.41 protocluster, with a mass of 2500~M$_{\odot}$ over 1.7~pc$^2$. To simplify the N$_2$H$^+$ line profile we extract the isolated hyperfine line component for kinematic analysis. We model this single line with up to 3 Gaussian components to constrain the kinematics of the dense gas immediately associated with star formation. The velocity components are well separated, most of the 1.3 mm-detected cores are located in subregions with 2 to 3 components, indicating kinematic complexity even at $\sim$ 2~kAU scales. Other core velocity tracers match the N$_2$H$^+$ velocities, indicating that the cores are still kinematically coupled to the maternal dense gas. The intensity-weighted position-velocity (PV) diagram shows 9 obvious ``V-shaped" converging velocity gradients (Figure A: top right panel) on $\sim$~small scales. These gradients have timescales of $\sim$67~kyr. This is short compared to the free fall time t$_{ff}\,=\,\,0.21$~Myr of the cloud, but large compared to the mean t$_{ff}\,=\,\sim$13~kyr of cores. We derive core mass accretion rates for the V-shapes. The values, in the range of 0.3~-~12.4~$\times~10^{-4}$~M$_{\odot}$~yr$^{-1}$, are consistent with literature values. The traditional PV diagram highlights the large-scale velocity structures in this region (Figure B: background emission map). We create a simple model of an infalling sphere, with a power law density profile. Its PV diagram matches the large scale structure present in the data (Figure B: gray shaded area), indicating that this protocluster is collapsing under gravity. From the large and small scale features, we conclude that cores form concurrently with the large-scale collapse in gas-dominated protoclusters, and required a time in the order of $\sim$~70~kyr to build up their mass (short compared to the $\sim$~500~kyr protostar lifetime).

Resumen:

The ALMA-IMF Large Program observed 15 massive protoclusters in two bands (1.3 and 3 mm), capturing multiple line, and continuum emission (e.g., Ginsburg et al. 2021; Motte et al. 2021). Here we study the massive filamentary protocluster G351.77, located at a distance of $\sim$ 2 kpc (Reyes et al. submitted). We trace the dense gas emission and kinematics via the N$_2$H$^{+}$ (1-0) line. To recover the emission, the 12M and 7M arrays were both combined and reduced to then be feathered with Total Power data, obtaining an image that captures the N$_2$H$^{+}$ emission over the protocluster and down to 2 kAU scales. The N$_2$H$^{+}$ hyperfine line profile is modeled with PySpecKit, fitting two velocity components, obtaining the Excitation temperature, Optical depth, Centroid velocity and Line width for each velocity component. In combination with the optical depth and an H$_2$ column density map derived from the 1.3 mm band, we estimated the N$_2$H$^{+}$ relative abundance $\sim$ (3.192 $\pm$ 0.813) $\times$ $10^{-10}$. We estimated a total mass of $\sim$ 864 $\pm$ 220 M$_{\odot}$. By examining the position-velocity diagrams at small scales, we observe infall signatures associated with 1.3 mm cores. In some cases, similar signatures were observed without related cores, suggesting the existence of cores below the 1.3 mm detection limits. The most prominent v-shape has an average of mass accretion rate $\sim$ 2.035 $\times$ $10^{-4}$ M$_{\odot}$/yr and an average timescale $\sim$ 18.67 kyr. The position-velocity diagram on large scales shows that the mother filament is separated into two velocity components in the protocluster. Most cores are found to be associated with the more blue-shifted sub-filament. Our analysis reveals that multiple velocity components pervade the protocluster, indicating kinematic complexity in the dense gas. Cores seem to prefer one velocity component of the gas, and their mass buildup timescales are $\sim$ 33 kyr.

Resumen:

Stars form in molecular clouds. These clouds are dense concentrations of H2 that are traditionally traced in external galaxies using transitions of CO or other, more complex molecules. CO observations in low metallicity systems are elusive as CO emission is weak and the low abundance of Carbon and dust prevents the shielding of the molecule from photo dissociation. Tracers of recent star formation, such as Halfa or far-ultraviolet (FUV) emission, show that most dwarfs contain young stars and star clusters, but CO observations often yield only upper limits. Recent observations suggest that molecular clouds traced by CO in the metal-poor ISM are small and the intense UV interstellar radiation fields (ISRFs) these unshielded environments at least partially photo-dissociate CO, thus eroding the clouds. Models predict that low metallicity galaxies have large reservoirs of CO-dark molecular gas and high CO-to-H2 conversion factors to compensate for the missing CO. We will review the latest results of the molecular cloud properties obtained with ALMA of star-forming regions at the lowest metallicities dwarf galaxies from the SMC (0.2 Zo) to WLM (0.1Zo). These studies provide key insights into the star formation process at low metallicities and are fundamental to understand the star formation at early times in the Universe.

Resumen:

Planetary nebulae (PNe) and symbiotic stars (SySts) offer crucial insights for understanding the late-stage stellar evolution of low and intermediate-mass stars. A significant aspect worth highlighting is that the former play an important role in the chemical evolution of the Galaxy, while the latter seem to be connected to the formation of type Ia supernovae. Currently, about 3,500 PNe and 300 SySts are known in the Milky Way, which shows a discrepancy of one order of magnitude with their expected number based on population synthesis calculations. This study aims to contribute towards the identification of new PNe and SySts in the Galaxy, reducing the discrepancy between the numbers of known and estimated objects and validating candidate selection methods. For this purpose, we utilize optical magnitudes from VPHAS+ and infrared magnitudes from AllWISE catalogs to apply novelty color criteria to select candidates. In order to confirm their nature, optical spectroscopic observations are carried out using the SOAR telescope. So far, we selected PN and SySt candidates and performed the observations of 10 PN and 3 SySt candidates. The results demonstrate that the new selection criteria, which combine optical and infrared data, have proven highly effective in identifying strong emission-line objects. The newly confirmed PNe and SySts as well as their spectroscopic properties will be shown in this presentation.

Resumen:

Building upon previous research on the emission of polycyclic aromatic hydrocarbons (PAHs) in the mid-infrared (mid-IR), the present work studies a sample of 28 local galaxies (D $\lesssim$ 30Mpc) from the Spitzer Survey of Near-infrared Galaxies (SINGS). All objects show optical signatures of an active galaxy nucleus (AGN), and PAHs are also detected. The sample covers 28 nuclear regions, one for each galaxy, and 40 extranuclear regions corresponding to some galaxies. Molecules in each region were identified by fitting them with the NASA Ames PAH IR Spectroscopic Database (PAHdb). The molecules present were categorized into families based on their composition: PAH, amorphous (molecules that contain only carbon in their formula), Polycyclic Aromatic Nitrogenous Hydrocarbons (PANH), and Polycyclic Aromatic Hydrocarbons with heteroatom (any atom other than hydrogen, carbon, or nitrogen). With this categorization, it is easy to notice, in general, that PAHs and amorphous ones, such as C24, have the highest flux contribution in the studied regions. Also, the C24 molecule has a remarkable contribution to the flux of some galaxies. In this preliminary study, when categorizing the molecules considering only the nuclear region, it is possible to notice that the percentage of PAH is predominant in most of the galaxies, while the amorphous ones predominate in the others. The percentages of PANH and heteroatom change little or nothing between the nuclear and extranuclear regions. The next goal of the research is to determine what conditions are causing the different flux contribution of each family of molecules depending on the environment. In addition, laboratory studies using the C24 molecule and PAHs with 24 carbon atoms will be carried out using the techniques of time-of-flight mass spectrometry (TOF-MS) and infrared spectroscopy (FTIR), to verify the stability and the pathways of break-down of these species under radiation field.

Resumen:

The cold to total HI ratio in the Galactic plane seems to remain approximately constant for galactocentric radius, $R_G$, between $\sim 10$ and $\sim 20$ kpc, despite the differences in physical conditions. In order to explore the possible role of radial variations of the velocity dispersion and the mean magnetic field on the radial control of the cold HI gas fraction, we use numerical simulations with cooling functions adapted to model HI gas at $R_G$ equal to 8.5, 11, 15 and 18 kpc. Models with different velocity dispersions mean magnetic field and forcing scales are analyzed. We find that, for the values of $R_G$ we consider, the combined effect of radial magnetic field variations and forcing scale is enough to maintain the cold HI mass fraction approximately constant between 11 and 18 kpc.

Resumen:

Turbulence and magnetic fields are components of our Galaxy’s interstellar medium and are tightly interconnected through complex plasma processes. In particular, the magnetic flux transport in the presence of magneto-hydrodynamic (MHD) turbulence in molecular clouds is an essential factor for understanding different processes involved in star formation. The theory of turbulent Reconnection Diffusion (RD), predicts the dependence of the effective diffusion coefficient of the magnetic field with the Mach Alfvénic number $M_A$ (which is the ratio between the turbulent velocity and the local Alfvén velocity). However, the current RD theory does not take into account the effects of compressibility which should be important in the regime of supersonic MHD turbulence present in molecular clouds. Therefore, we aim to determine, with 3D MHD turbulence simulations, the dependence of the magnetic flux in different regimes of compressible turbulence, characterized by different sonic Mach numbers $M_S$. In order to measure the diffusion of the magnetic field in the simulations, we analyze the temporal statistics of the tracer particles' velocity to obtain their diffusion rate. Our results confirm the RD hypothesis of the correspondence of the magnetic field lines’ diffusion with the fluid Lagrangian particles' diffusion. Nonetheless, the incompressible turbulence is shown to behave as predicted by RD theory: the presence of a strong magnetic field suppresses the diffusion and, therefore, $D \propto M^3_A$. In our compressible simulations, the RD efficiency seems to increase when the turbulence is supersonic, with $D \propto M^1_A$ in our simulations with $M_S = 3$. This quantitative characterization of the effective diffusion coefficient is important for modeling protostellar disk formation in turbulent molecular clouds and for the evaluation of the efficiency of this transport process when compared to other mechanisms, for instance Ambipolar Diffusion.

Resumen:

We study the dense N$_2$H$^+$ (1-0) gas in the nearby massive (1.7 x 10$^3$ M$_{\odot}$) protocluster G012.80, located at a distance = 2.4 kpc. G12 was observed as part of the ALMA-IMF large program (Motte et al., 2022). Here we integrated the N$_2$H$^+$ line with different complementary lines (H41$\alpha$, SiO, C$^{18}$O, and dense core catalogs). G12 exhibits a plane-of-the-sky swirling structure in N$_2$H$^+$, with H41$\alpha$ emission at the center where N$_2$H$^+$ is absent. We model the blended N$_2$H$^+$ hyperfine lines, and our analysis revealed that G12 is dominated by multiple velocity components. Interestingly, the structures associated with two velocity components are mostly correlated with SiO emission. We identified strong velocity gradients in the intensity-weighted position-velocity (PV) diagrams, primarily related to the two velocity component emission. These gradients correspond to timescales of approximately 2 - 0.06 Myr, with even shorter timescales observed near the protocluster center. The PV structures exhibit twisting and turning patterns connected to the main N2H+ filaments on small scales (~2 kAU), which seem to be associated with core accretion. Additionally, we discovered a potential signature of rotation in the northern part of G12, traced mostly in a single velocity component, with an absence of detected cores potentially indicating youth. To analyze this rotation signature, we combine column density estimates for the region with the velocity field in order to create a mass map and determine the forces related to rotation (gravitational and centripetal). Our next steps involve analysis of this rotation signature and to create mass profiles in the southern part of G12 where the current N(H$_2$) data is well detected.

Resumen:

Typically, integrated radio frequency continuum spectra of supernova remnants (SNRs) exhibit a power-law form due to their synchrotron emission. In numerous cases, these spectra show an exponential turnover, long assumed due to thermal free-free absorption in the interstellar medium. We use a compilation of Galactic radio continuum SNR spectra, with and without turnovers, to constrain the distribution of the absorbing ionized gas. We introduce a novel parameterization of SNR spectra in terms of a characteristic frequency $v_*$, which depends both on the absorption turnover frequency and the power-law slope. Normalizing to $v_*$ and to the corresponding flux density, $S_*$, we demonstrate that the stacked spectra of our sample reveal a similarity in behavior with low scatter (r.m.s. $\sim$15\%), and a unique exponential drop-off fully consistent with the predictions of a free-free absorption process. Observed SNRs, whether exhibiting spectral turnovers or not, appear to be spatially well mixed in the Galaxy without any evident segregation between them. Moreover, their Galactic distribution does not show a correlation with general properties such as heliocentric distance or Galactic longitude, as might have been expected if the absorption were due to a continuous distribution of ionized gas. However, it naturally arises if the absorbers are discretely distributed, as suggested by early low-frequency observations. Modelling based on Hii regions tracking Galactic spiral arms successfully reproduces the patchy absorption observed to date. While more extensive statistical datasets should yield more precise spatial models of the absorbing gas distribution, our present conclusion regarding its inhomogeneity will remain robust.