Astrophysics

We investigate the infrared (IR) emission of high-redshift ( z?? ), highly star-forming ( SFR>100 M ??yr ?? ) galaxies, with/without Active Galactic Nuclei (AGN), using a suite of cosmological simulations featuring dust radiative transfer. Synthetic Spectral Energy Distributions (SEDs) are used to quantify the relative contribution of stars/AGN to dust heating. In dusty ( M d ??? 10 7 M ??) galaxies, ??0??0% of the UV radiation is obscured by dust inhomogeneities on scales ??00 pc. In runs with AGN, a clumpy, warm ( ??50 K) dust component co-exists with a colder ( ??0 K) and more diffuse one, heated by stars. Warm dust provides up to 50% of the total IR luminosity, but only ??.1% of the total mass content. The AGN boosts the MIR flux by 10??00? with respect to star forming galaxies, without significantly affecting the FIR. Our simulations successfully reproduce the observed SED of bright ( M UV ?��?26 ) z?? quasars, and show that these objects are part of complex, dust-rich merging systems, containing multiple sources (accreting BHs and/or star forming galaxies) in agreement with recent HST and ALMA observations. Our results show that the proposed ORIGINS missions will be able to investigate the MIR properties of dusty star forming galaxies and to obtain good quality spectra of bright quasars at z?? . Finally, the MIR-to-FIR flux ratio of faint ( M UV ?��?24 ) AGN is >10? higher than for normal star forming galaxies. This implies that combined JWST/ORIGINS/ALMA observations will be crucial to identify faint and/or dust-obscured AGN in the distant Universe.

The current tension between the direct and the early Universe measurements of the Hubble Constant, H 0 , requires detailed scrutiny of all the data and methods used in the studies on both sides of the debate. The Cepheids in the type Ia supernova (SNIa) host galaxy NGC 5584 played a key role in the local measurement of H 0 . The SH0ES project used the observations of this galaxy to derive a relation between Cepheids' periods and ratios of their amplitudes in different optical bands of the Hubble Space Telescope (HST), and used these relations to analyse the light curves of the Cepheids in around half of the current sample of local SNIa host galaxies. In this work, we present an independent detailed analysis of the Cepheids in NGC 5584. We employ different tools for our photometric analysis and a completely different method for our light curve analysis, and we do not find a systematic difference between our period and mean magnitude measurements compared to those reported by SH0ES. By adopting a period-luminosity relation calibrated by the Cepheids in the Milky Way, we measure a distance modulus μ=31.810±0.047 (mag) which is in agreement with μ=31.786±0.046 (mag) measured by SH0ES. In addition, the relations we find between periods and amplitude ratios of the Cepheids in NGC 5584 are significantly tighter than those of SH0ES and their potential impact on the direct H 0 measurement will be investigated in future studies.

We present results of sub-arcsec ALMA observations of CO(2-1) and CO(5-4) toward a massive main sequence galaxy at z = 1.45 in the SXDS/UDS field, aiming at examining the internal distribution and properties of molecular gas in the galaxy. Our target galaxy consists of the bulge and disk, and has a UV clump in the HST images. The CO emission lines are clearly detected and the CO(5-4)/CO(2-1) flux ratio (R_52) is ~1, similar to that of the Milky Way. Assuming a metallicity dependent CO-toH_2 conversion factor and a CO(2-1)/CO(1-0) flux ratio of 2 (the Milky Way value), the molecular gas mass and the gas mass fraction (f_gas = molecular gas mass / (molecular gas mass + stellar mass)) are estimated to be ~1.5x10^11 M_Sun and ~0.55, respectively. We find that R_52 peak coincides with the position of the UV clump and its value is approximately two times higher than the galactic average. This result implies high gas density and/or high temperature in the UV clump, which qualitatively agrees with a numerical simulation of a clumpy galaxy. The CO(2-1) distribution is well represented by a rotating disk model and its half-light radius is ~2.3 kpc. Compared to the stellar distribution, the molecular gas is more concentrated in the central region of the galaxy. We also find that f_gas decreases from ~0.6 at the galactic center to ~0.2 at 3xhalf-light radius, indicating that the molecular gas is distributed in more central region of the galaxy than stars and seems to associate with the bulge rather than the stellar disk.

Using radio observations with the Green Bank Telescope, evidence has now been found for a second five-membered ring in the dense cloud Taurus Molecular Cloud-1 (TMC-1). Based on additional observations of an ongoing, large-scale, high-sensitivity spectral line survey (GOTHAM) at centimeter wavelengths toward this source, we have used a combination of spectral stacking, Markov chain Monte Carlo (MCMC), and matched filtering techniques to detect 2-cyanocyclopentadiene, a low-lying isomer of 1-cyanocyclopentadiene, which was recently discovered there by the same methods. The new observational data also yields a considerably improved detection significance for the more stable isomer and evidence for several individual transitions between 23 - 32 GHz. Through our MCMC analysis, we derive total column densities of 8.3? 10 11 and 1.9? 10 11 cm ?? for 1- and 2-cyanocyclopentadiene respectively, corresponding to a ratio of 4.4(6) favoring the former. The derived abundance ratios point towards a common formation pathway - most likely being cyanation of cyclopentadiene by analogy to benzonitrile.

We present piXedfit, pixelized spectral energy distribution (SED) fitting, a Python package that provides tools for analyzing spatially resolved properties of galaxies using multiband imaging data alone or in combination with integral field spectroscopy (IFS) data. piXedfit has six modules that can handle all tasks in the spatially resolved SED fitting. The SED fitting module uses the Bayesian inference technique with two kinds of posteriors sampling methods: Markov Chain Monte Carlo (MCMC) and random densely-sampling of parameter space (RDSPS). We test the performance of the SED fitting module using mock SEDs of simulated galaxies from IllustrisTNG. The SED fitting with both posteriors sampling methods can recover physical properties and star formation histories of the IllustrisTNG galaxies well. We further test the performance of piXedfit modules by analyzing 20 galaxies observed by the CALIFA and MaNGA surveys. The data comprises of 12-band imaging data from GALEX, SDSS, 2MASS, and WISE, and the IFS data from CALIFA or MaNGA. piXedfit can spatially match (in resolution and sampling) of the imaging and IFS data. By fitting only the photometric SEDs, piXedfit can predict the spectral continuum, D n 4000 , H α , and H β well. The star formation rate (SFR) derived by piXedfit is consistent with that derived from H α emission. The RDSPS method gives equally good fitting results as the MCMC and it is much faster than the MCMC. piXedfit is a versatile tool equipped with a parallel computing module for efficient analysis of large datasets, and will be made publicly available (this https URL).

Magnetic fields play such essential roles in star formation as transporting angular momentum and driving outflows from a star-forming cloud, thereby controlling the formation efficiency of a circumstellar disc and also multiple stellar systems. The coupling of magnetic fields to the gas depends on its ionization degree. We calculate the temperature evolution and ionization degree of a cloud for various metallicities of Z/Zsun = 1e-6, 1e-5, 1e-4, 1e-3, 1e-2, 1e-1, and 1. We update the chemical network by reversing all the gas-phase processes and by considering grain-surface chemistry, including grain evaporation, thermal ionization of alkali metals, and thermionic emission from grains. The ionization degree at nH ~ 1e15-1e19 /cm^3 becomes up to eight orders of magnitude higher than that obtained in the previous model, owing to the thermionic emission and thermal ionization of K and Na, which have been neglected so far. Although magnetic fields dissipate owing to ambipolar diffusion or Ohmic loss at nH < 1e15 /cm^3, the fields recover strong coupling to the gas at nH ~ 1e15 /cm^3, which is lower by a few orders of magnitude compared to the previous work. We develop a reduced chemical network by choosing processes relevant to major coolants and charged species. The reduced network consists of 104 (161) reactions among 28 (38) species in the absence (presence, respectively) of ionization sources. The reduced model includes H2 and HD formation on grain surfaces as well as the depletion of O, C, OH, CO, and H2O on grain surfaces.

We demonstrate that by combining two robust theoretical quantum chemistry calculation techniques, stepwise ionization of C60 fullerene by UV and extreme UV photons can in principle occur up to a limit as high as q=+26 before coulomb explosion of the cage. Furthermore, these highly ionized forms exhibit a comparable structural and bonding stability as for the neutral fullerene. Certain astrophysical sources like the central stars of planetary nebulae and the hottest white dwarf stars have sufficiently hard UV radiation fields that can result in a series of highly charged C60(q+) species from q=1 up to q=16. Harsher environments, like hot X-ray bubbles in planetary nebulae, X-ray binaries and other sources, may further push the ionization right up to the q=+26 limit. These remarkable theoretical findings add new avenues to complex ion/molecule reactions, the chemistry of fragmentation products and additional pathways for spreading carbon throughout the universe. The implications for the emerging field of astrochemistry of C60 fullerene in all its possible states could be profound.

Ram Pressure Stripping can remove gas from satellite galaxies in clusters via a direct interaction between the intracluster medium (ICM) and the interstellar medium. This interaction is generally thought of as a contact force per area, however we point out that these gases must interact in a hydrodynamic fashion, and argue that this will lead to mixing of the galactic gas with the ICM wind. We develop an analytic framework for how mixing is related to the acceleration of stripped gas from a satellite galaxy. We then test this model using three "wind-tunnel" simulations of Milky Way-like galaxies interacting with a moving ICM, and find excellent agreement with predictions using the analytic framework. Focusing on the dense clumps in the stripped tails, we find that they are nearly uniformly mixed with the ICM, indicating that all gas in the tail mixes with the surroundings, and dense clumps are not separate entities to be modeled differently than diffuse gas. We find that while mixing drives acceleration of stripped gas, the density and velocity of the surrounding wind will determine whether the mixing results in the heating of stripped gas into the ICM, or the cooling of the ICM into dense clouds.

We present the updated photometric calibration of the twelve optical passbands for the Javalambre Photometric Local Universe Survey (J-PLUS) second data release (DR2), comprising 1088 pointings of two square degrees, and study the systematic impact of metallicity in the stellar locus technique. The [Fe/H] metallicity from LAMOST DR5 for 146184 high-quality calibration stars, defined with S/N > 10 in J-PLUS passbands and S/N > 3 in Gaia parallax, was used to compute the metallicity-dependent stellar locus (ZSL). The initial homogenization of J-PLUS photometry, performed with a unique stellar locus, was refined by including the metallicity effect in colours via the ZSL. The variation of the average metallicity along the Milky Way produces a systematic offset in J-PLUS calibration. This effect is well above 1% for the bluer passbands and amounts 0.07, 0.07, 0.05, 0.03, and 0.02 mag in u, J0378, J0395, J0410, and J0430, respectively. We modelled this effect with the Milky Way location of the J-PLUS pointing, providing also an updated calibration for those observations without LAMOST information. The estimated accuracy in the calibration after including the metallicity effect is at 1% level for the bluer J-PLUS passbands and below for the rest. We conclude that photometric calibration with the stellar locus technique is prone to significant systematic bias along the Milky Way location for passbands bluer than lambda = 4500 A. The updated calibration method for J-PLUS DR2 reaches 1-2% precision and 1% accuracy for twelve optical filters within an area of 2176 square degrees.

We present the theoretical framework to efficiently solve the Jeans equations for multi-component axisymmetric stellar systems, focusing on the scaling of all quantities entering them. The models may include an arbitrary number of stellar distributions, a dark matter halo, and a central supermassive black hole; each stellar distribution is implicitly described by a two- or three-integral distribution function, and the stellar components can have different structural (density profile, flattening, mass, scale-length), dynamical (rotation, velocity dispersion anisotropy), and population (age, metallicity, initial mass function, mass-to-light ratio) properties. In order to determine the ordered rotational velocity and the azimuthal velocity dispersion fields of each component, we introduce a decomposition that can be used when the commonly adopted Satoh decomposition cannot be applied. The scheme developed is particularly suitable for a numerical implementation; we describe its realisation within our code JASMINE2, optimised to maximally exploit the scalings allowed by the Poisson and the Jeans equations, also in the post-processing procedures. As applications, we illustrate the building of three multi-component galaxy models with two distinct stellar populations, a central black hole, and a dark matter halo; we also study the solution of the Jeans equations for an exponential thick disc, and for its multi-component representation as the superposition of three Miyamoto-Nagai discs. A useful general formula for the numerical evaluation of the gravitational potential of factorised thick discs is finally given.