Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>We construct empirical models of star-forming galaxy evolution assuming that individual galaxies evolve along well-known scaling relations between stellar mass, gas mass, and star formation rate following a simple description of chemical evolution. We test these models by a comparison with observations and detailed Magneticum high-resolution hydrodynamic cosmological simulations. Galaxy star formation rates, stellar masses, gas masses, ages, interstellar medium, and stellar metallicities are compared. It is found that these simple look-back models capture many of the crucial aspects of galaxy evolution reasonably well. Their key assumption of a redshift-dependent power-law relationship between galaxy interstellar medium gas mass and stellar mass is in agreement with the outcome of the complex Magneticum simulations. Star formation rates decline toward lower redshift not because galaxies are running out of gas, but because the fraction of the cold interstellar medium gas, which is capable of producing stars, becomes significantly smaller. Gas accretion rates in both model approaches are of the same order of magnitude. Metallicity in the Magneticum simulations increases with the ratio of stellar mass to gas mass as predicted by the look-back models. The mass–metallicity relationships agree, and the star formation rate dependence of these relationships is also reproduced. We conclude that these simple models provide a powerful tool for constraining and interpreting more complex models based on cosmological simulations and for population synthesis studies analyzing the integrated spectra of stellar populations.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We use the FIRE-2 cosmological simulations to study the formation of a quasi-static, virial-temperature gas phase in the circumgalactic medium (CGM) at redshifts 0 &lt; <jats:italic>z</jats:italic> &lt; 5 and how the formation of this virialized phase affects the evolution of galactic disks. We demonstrate that when the halo mass crosses ∼10<jats:sup>12</jats:sup> <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub>, the cooling time of shocked gas in the inner CGM (∼0.1<jats:italic>R</jats:italic> <jats:sub>vir</jats:sub>, where <jats:italic>R</jats:italic> <jats:sub>vir</jats:sub> is the virial radius) exceeds the local free-fall time. The inner CGM then experiences a transition from on average subvirial temperatures (<jats:italic>T</jats:italic> ≪ <jats:italic>T</jats:italic> <jats:sub>vir</jats:sub>), large pressure fluctuations, and supersonic inflow/outflow velocities to virial temperatures (<jats:italic>T</jats:italic> ∼ <jats:italic>T</jats:italic> <jats:sub>vir</jats:sub>), uniform pressures, and subsonic velocities. This transition occurs when the outer CGM (∼0.5<jats:italic>R</jats:italic> <jats:sub>vir</jats:sub>) is already subsonic and has a temperature ∼<jats:italic>T</jats:italic> <jats:sub>vir</jats:sub>, indicating that the longer cooling times at large radii allow the outer CGM to virialize at lower halo masses than the inner CGM. This outside-in CGM virialization scenario is in contrast with inside-out scenarios commonly envisioned based on more idealized simulations. We demonstrate that inner CGM virialization coincides with abrupt changes in the central galaxy and its stellar feedback: the galaxy settles into a stable rotating disk, star formation transitions from “bursty” to “steady,” and stellar-driven galaxy-scale outflows are suppressed. Our results thus suggest that CGM virialization is initially associated with the formation of rotation-dominated thin galactic disks, rather than with the quenching of star formation as often assumed.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The interstellar turbulence is magnetized and thus anisotropic. The anisotropy of turbulent magnetic fields and velocities is imprinted in the related observables, rotation measures (RMs), and velocity centroids (VCs). This anisotropy provides valuable information on both the direction and strength of the magnetic field. However, its measurement is difficult, especially in highly supersonic turbulence in cold interstellar phases, due to the distortions by isotropic density fluctuations. By using 3D simulations of supersonic and sub-Alfvénic magnetohydrodynamic (MHD) turbulence, we find that the problem can be alleviated when we selectively sample the volume filling low-density regions in supersonic MHD turbulence. Our results show that in these low-density regions the anisotropy of RM and VC fluctuations depends on the Alfvénic Mach number as <jats:inline-formula> <jats:tex-math> <?CDATA ${M}_{{\rm{A}}}^{-4/3}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabe403ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>. This anisotropy−<jats:italic>M</jats:italic> <jats:sub>A</jats:sub> relation is theoretically expected for sub-Alfvénic MHD turbulence and confirmed by our synthetic observations of <jats:sup>12</jats:sup>CO emission. It provides a new method for measuring the plane-of-the-sky magnetic fields in cold interstellar phases.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Nonlinear ion-acoustic waves, ion holes, and electron holes have been observed on the Parker Solar Probe at a heliocentric distance of 35 solar radii. These time domain structures contain millisecond duration electric field spikes of several mV m<jats:sup>−1</jats:sup>. They are observed inside or at boundaries of switchbacks in the background magnetic field. Their presence in switchbacks indicates that both electron- and ion-streaming electrostatic instabilities occur there to thermalize electron and ion beams.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The underlying distribution of galaxies’ dust spectral energy distributions (SEDs) (i.e., their spectra reradiated by dust from rest-frame ∼3 <jats:italic>μ</jats:italic>m to 3 mm) remains relatively unconstrained owing to a dearth of far-IR/(sub)millimeter data for large samples of galaxies. It has been claimed in the literature that a galaxy’s dust temperature—observed as the wavelength where the dust SED peaks (<jats:italic>λ</jats:italic> <jats:sub>peak</jats:sub>)—is traced most closely by its specific star formation rate (sSFR) or parameterized “distance” to the SFR–<jats:italic>M</jats:italic> <jats:sub>⋆</jats:sub> relation (the galaxy “main sequence”). We present 024 resolved 870 <jats:italic>μ</jats:italic>m ALMA dust continuum observations of seven <jats:italic>z</jats:italic> = 1.4–4.6 dusty star-forming galaxies chosen to have a large range of well-constrained luminosity-weighted dust temperatures. We also draw on similar-resolution dust continuum maps from a sample of ALESS submillimeter galaxies from Hodge et al (2016). We constrain the physical scales over which the dust radiates and compare those measurements to characteristics of the integrated SED. We confirm significant correlations of <jats:italic>λ</jats:italic> <jats:sub>peak</jats:sub> with both <jats:italic>L</jats:italic> <jats:sub>IR</jats:sub> (or SFR) and Σ<jats:sub>IR</jats:sub> (∝SFR surface density). We investigate the correlation between log<jats:sub>10</jats:sub>(<jats:italic>λ</jats:italic> <jats:sub>peak</jats:sub>) and log<jats:sub>10</jats:sub>(Σ<jats:sub>IR</jats:sub>) and find the relation to hold as would be expected from the Stefan–Boltzmann law, or the effective size of an equivalent blackbody. The correlations of <jats:italic>λ</jats:italic> <jats:sub>peak</jats:sub> with sSFR and distance from the SFR–<jats:italic>M</jats:italic> <jats:sub>⋆</jats:sub> relation are less significant than those for Σ<jats:sub>IR</jats:sub> or <jats:italic>L</jats:italic> <jats:sub>IR</jats:sub>; therefore, we conclude that the more fundamental tracer of galaxies’ luminosity-weighted integrated dust temperatures are indeed their star formation surface densities in line with local universe results, which relate closely to the underlying geometry of dust in the interstellar medium.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Using a 3D global solver of the linearized Euler equations, we model acoustic oscillations over background velocity flow fields of single-cell meridional circulation with deep and shallow return flows as well as double-cell meridional circulation with strong and weak reversals. The velocities are generated using a mean-field hydrodynamic and dynamo model—moving through the regimes with minimal parameter changes, counterrotation near the base of the tachocline is induced by sign inversion of the nondiffusive action of turbulent Reynolds stresses (Λ-effect) due to the radial inhomogeneity of the Coriolis number. By mimicking the stochastic excitation of resonant modes in the convective interior, we simulate realization noise present in solar observations. Using deep-focusing to analyze differences in travel-time signatures between the four regimes, as well as comparing to solar observations, we show that current helioseismology techniques may offer important insights about the location and strength of the return flow; however, it may not currently be possible to definitively distinguish between profiles of single-cell or double-cell meridional circulation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We study the behavior and properties of the solar wind using a 2.5D Alfvén wave (AW)-driven wind model. We first systematically compare the results of an AW-driven wind model with a polytropic approach. Polytropic magnetohydrodynamic wind models are thermally driven, while AWs act as additional acceleration and heating mechanisms in the AW-driven model. We confirm that an AW-driven model is required to reproduce the observed bimodality of slow and fast solar winds. We are also able to reproduce the observed anticorrelation between the terminal wind velocity and the coronal source temperature with the AW-driven wind model. We also show that the wind properties along an 11 yr cycle differ significantly from one model to the other. The AW-driven model again shows the best agreement with observational data. Indeed, solar surface magnetic field topology plays an important role in the AW-driven wind model, as it enters directly into the input energy sources via the Poynting flux. On the other hand, the polytropic wind model is driven by an assumed pressure gradient; thus, it is relatively less sensitive to the surface magnetic field topology. Finally, we note that the net torque spinning down the Sun exhibits the same trends in the two models, showing that the polytropic approach still correctly captures the essence of stellar winds.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We have investigated the stellar and interstellar content of the distant star formation region IRAS 17591-2228 (WISE H <jats:sc>ii</jats:sc> region GAL 007.47+0.06). It is associated with a water maser, whose parallax distance is <jats:inline-formula> <jats:tex-math> <?CDATA $d={20.4}_{-2.2}^{+2.8}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabec6fieqn1.gif" xlink:type="simple" /> </jats:inline-formula> kpc, supported by independent measurements of proper motion and radial velocity. It is projected in the same direction as an extremely red (<jats:italic>J</jats:italic>−<jats:italic>K</jats:italic> <jats:sub> <jats:italic>S</jats:italic> </jats:sub> ∼ 6 mag) group of stars, and a shell of mid-infrared emission. We qualify the group of stars as a cluster candidate, VVV CL177. Its radius spans between 0.′45 and 1′ and contains at least two young stellar objects with an extreme extinction near <jats:inline-formula> <jats:tex-math> <?CDATA ${A}_{{\rm{V}}}\sim 40$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabec6fieqn2.gif" xlink:type="simple" /> </jats:inline-formula> mag. Yet more analysis will be required to determine if it is a real single cluster associated with the water maser. The <jats:sup>13</jats:sup>CO emissions at the radial velocity of the maser corresponds to the mid-infrared emission.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this work, we derive magnetic toroids from surface magnetograms by employing a novel optimization method, based on the trust region reflective algorithm. The toroids obtained in this way are combinations of Fourier modes (amplitudes and phases) with low longitudinal wavenumbers. The optimization also estimates the latitudinal width of the toroids. We validate the method using synthetic data, generated as random numbers along a specified toroid. We compute the shapes and latitudinal widths of the toroids via magnetograms, generally requiring several <jats:italic>m</jats:italic>'s to minimize residuals. A threshold field strength is chosen to include all active regions in the magnetograms for toroid derivation, while avoiding non-contributing weaker fields. Higher thresholds yield narrower toroids, with an <jats:italic>m</jats:italic> = 1 dominant pattern. We determine the spatiotemporal evolution of toroids by optimally weighting the amplitudes and phases of each Fourier mode for a sequence of five Carrington Rotations (CRs) to achieve the best amplitude and phases for the middle CR in the sequence. Taking more than five causes “smearing” or degradation of the toroid structure. While this method applies no matter the depth at which the toroids actually reside inside the Sun, by comparing their global shape and width with analogous patterns derived from magnetohydrodynamic (MHD) tachocline shallow water model simulations, we infer that their origin is at/near the convection zone base. By analyzing the “Halloween” storms as an example, we describe features of toroids that may have caused the series of space weather events in 2003 October–November. Calculations of toroids for several sunspot cycles will enable us to find similarities/differences in toroids for different major space weather events.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report on the discovery of a promising candidate for a black widow (BW) millisecond pulsar binary, 4FGL J0336.0+7502, which shows many pulsar-like properties in the 4FGL-DR2 catalog. Within the 95% error region of the LAT source, we identified an optical counterpart with a clear periodicity at <jats:italic>P</jats:italic> <jats:sub>orb</jats:sub> = 3.718178(9) hr using the Bohyunsan 1.8 m Telescope, the Lulin One-meter Telescope, the Canada–France–Hawaii Telescope, and Gemini-North. At the optical position, an X-ray source was marginally detected in the Swift/X-Ray Telescope archival data, and the detection was confirmed by our Chandra/ACIS DDT observation. The spectrum of the X-ray source can be described by a power-law model of Γ<jats:sub> <jats:italic>x</jats:italic> </jats:sub> = 1.6 ± 0.7 and <jats:inline-formula> <jats:tex-math> <?CDATA ${F}_{0.3\mbox{--}7\mathrm{keV}}={3.5}_{-1.0}^{+1.2}\times {10}^{-14}$?> </jats:tex-math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjabeb76ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> erg cm<jats:sup>−2</jats:sup> s<jats:sup>−1</jats:sup>. The X-ray photon index and the low X-ray-to-<jats:italic>γ</jats:italic>-ray flux ratio (i.e., &lt;1%) are both consistent with that of many known BW pulsars. There is also a hint of an X-ray orbital modulation in the Chandra data, although the significance is very low (1.3<jats:italic>σ</jats:italic>). If the pulsar identity and the X-ray modulation are confirmed, it would be the fifth BW millisecond pulsar binary that showed an orbitally modulated emission in X-rays.</jats:p>