Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>The formation of hot stars out of the cold interstellar medium lies at the heart of astrophysical research. Understanding the importance of magnetic fields during star formation remains a major challenge. With the advent of the Atacama Large Millimeter Array, the potential to study magnetic fields by polarization observations has tremendously progressed. However, the major question remains how much magnetic fields shape the star formation process or whether gravity is largely dominating. Here, we show that for the high-mass star-forming region G327.3 the magnetic field morphology appears to be dominantly shaped by the gravitational contraction of the central massive gas core where the star formation proceeds. We find that in the outer parts of the region, the magnetic field is directed toward the gravitational center of the region. Filamentary structures feeding the central core exhibit U-shaped magnetic field morphologies directed toward the gravitational center as well, again showing the gravitational drag toward the center. The inner part then shows rotational signatures, potentially associated with an embedded disk, and there the magnetic field morphology appears to be rotationally dominated. Hence, our results demonstrate that for this region gravity and rotation are dominating the dynamics and shaping the magnetic field morphology.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>There is a dense group of OB and Wolf–Rayet stars within a fraction of a parsec from the supermassive black hole (SMBH) at the Galactic Center. These stars appear to be coeval and relatively massive. A subgroup of these stars orbits on the same plane. If they emerged with low- to modest-eccentricity orbits from a common gaseous disk around the central SMBH, their inferred life span would not be sufficiently long to account for the excitation of their high orbital eccentricity through dynamical relaxation. Here we analyze the secular perturbation of Galactic Center stars by an intermediate-mass companion (IMC) as a potential mechanism to account for these young disk stars’ high eccentricity. This IMC may be either an intermediate-mass black hole or a compact cluster such as IRS 13E. If its orbital angular momentum vector is antiparallel to that of the disk stars, this perturbation would be effective in exciting the eccentricity of stars with orbital precession rates that resonate with the IMC’s precession rate. If it orbits around the SMBH in the same direction as the disk stars, the eccentricity of the young stars can still be highly excited by the IMC during the depletion of their natal disk, possibly associated with the launch of the Fermi bubble. In this scenario, the IMC’s precession rate decreases, and its secular resonance sweeps through the proximity of the young stars. We carry out numerical simulations with various inclination angles between the orbits of the IMC and the disk stars and show that this secular interaction is a robust mechanism to excite the eccentricity and inclination of some disk stars.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Nuclear stellar clusters are common in the center of galaxies. We consider the possibility that their progenitors assumed to be globular clusters may have formed elsewhere, migrated to, and assembled near their present location. The main challenge for this scenario is whether globular clusters can withstand the tidal field of their host galaxies. Our analysis suggests that provided the mass-density distribution of background potential is relatively shallow, as in some galaxies with relatively flat surface brightness profiles, the tidal field near the center of galaxies may be shown to be able to compress rather than disrupt a globular cluster at a distance from the center much smaller than the conventionally defined “tidal disruption radius” <jats:italic>r</jats:italic> <jats:sub> <jats:italic>t</jats:italic> </jats:sub>. To do so, we adopt a previously constructed formalism and consider the secular evolution of star clusters with a homogeneous mass-density distribution. We analytically solve the secular equations in the limit that the mass density of stars in the galactic center approaches a uniform distribution. Our model indicates that a star cluster could travel to distances much smaller than <jats:italic>r</jats:italic> <jats:sub> <jats:italic>t</jats:italic> </jats:sub> without disruption, thus potentially contributing to the formation of the nuclear cluster. However, appropriate numerical <jats:italic>N</jats:italic>-body simulations are needed to confirm our analytic findings.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>An analytical approach is proposed to study the evolution of the star-forming galaxy (SFG) main sequence (MS) and the fraction of dust-obscured star formation (SF) up to <jats:italic>z</jats:italic> ∼ 4. Far-ultraviolet (FUV) and infrared (IR) star formation rates (SFRs) are described as conditional probability functions of <jats:italic>M</jats:italic> <jats:sub>*</jats:sub>. We convolve them with the galaxy stellar mass function (GSMF) of SFGs to derive the FUV and IR luminosity functions (LFs). The two SF modes formalism is used to describe starburst galaxies. By fitting observed FUV and IR LFs, the parameterization of SFR<jats:sub>FUV</jats:sub>−<jats:italic>M</jats:italic> <jats:sub>*</jats:sub> and SFR<jats:sub>IR</jats:sub>− <jats:italic>M</jats:italic> <jats:sub>*</jats:sub> is constrained. Our derived SFR<jats:sub>FUV+IR</jats:sub>−<jats:italic>M</jats:italic> <jats:sub>*</jats:sub> reproduces the evolution of the MS as compared to other observational inferences. At any redshift, we find that the sSFR<jats:sub>FUV+IR</jats:sub>–<jats:italic>M</jats:italic> <jats:sub>*</jats:sub> relation for MS SFGs approaches a power law at the high-mass end. At lower masses, it bends, and eventually, the slope sign changes from negative to positive at very low masses. At <jats:italic>z</jats:italic> ∼ 0, this change of sign is at <jats:italic>M</jats:italic> <jats:sub>*</jats:sub> ∼ 5 × 10<jats:sup>8</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, close to the dust-obscured SF regime, <jats:italic>M</jats:italic> <jats:sub>*</jats:sub> ∼ 6 × 10<jats:sup>8</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>. The slope sign change is related to the knee of the FUV LF. Our derived dust-obscured fractions agree with previous determinations at 0 ≤ <jats:italic>z</jats:italic> ≤ 2.5. Dust-obscured fractions depend strongly on mass with almost no dependence on redshift at <jats:italic>z</jats:italic> ≳ 1.2. At <jats:italic>z</jats:italic> ≲ 0.75, high-mass galaxies become more “transparent” compared to their high-redshift counterparts. On the other hand, low- and intermediate-mass galaxies have become more obscured by dust. The joint evolution of the GSMF and the FUV and IR LFs is a promising approach to study mass growth and dust formation/destruction mechanisms.</jats:p>