Spectroscopic Diagnostics of the Mid-Infrared Features of the Dark Globule, DC 314.8-5.1, with the Spitzer Space Telescope

We present an analysis of the mid-infrared spectra, obtained from the Spitzer Space Telescope, of the dark globule, DC 314.8--5.1, which is at the onset of low-mass star formation. The target has a serendipitous association with a B-type field star, which illuminates a reflection nebula in the cloud. We focus on the polycyclic aromatic hydrocarbon (PAH) emission features prevalent throughout the mid-infrared range. The analysis of the spectra with the PAHFIT software as well as pypahdb package, shows that (i) the intensities of PAH features decrease over distance from the ionizing star toward the cloud center, some however showing a saturation at larger distances; (ii) the relative intensities of the 6.2 and 8.6 features with respect to the 11.2 micron feature remain high throughout the globule, suggesting a larger cation-to-neutral PAH ratio of the order of unity; the breakdown from pypahdb confirms a high ionized fraction within the cloud; (iii) the pypahdb results display a decrease in large PAH fraction with increased distance from HD 130079, as well as a statistically significant correlation between the large size fraction and the ionized fraction across the globule; (iv) the 7.7 PAH feature displays a peak nearer to 7.8 microns, suggesting a chemically processed PAH population with a small fraction of UV-processed PAHs; (v) the H2 S(0) line is detected at larger distances from the ionizing star. All in all, our results suggest divergent physical conditions within the quiescent cloud DC 314.8--5.1 as compared to molecular clouds with ongoing starformation.Comment: Accepted for publication by the Astrophysical Journa

Multiwavelength Study of Dark Globule DC 314.8-5.1: Point Source Identification and Diffuse Emission Characterization

We present an analysis of multi-wavelength observations of the dark globule DC\,314.8--5.1, using data from the Gaia optical, 2MASS near-infrared, and WISE mid-infrared surveys, dedicated imaging with the Spitzer Space Telescope, and X-ray data obtained with the Swift-XRT Telescope (XRT). The main goal was to identify possible pre-main sequence stars (PMSs) and young stellar objects (YSOs) associated with the globule. For this, we studied the infrared colors of all point sources within the boundaries of the cloud. After removing sources with non-stellar spectra, we investigated the Gaia parallaxes for the YSO candidates, and found that none are physically related to DC\,314.8--5.1. In addition, we searched for X-ray emission from pre-main sequence stars with Swift-XRT, and found no 0.5--10\,keV emission down to a luminosity level $\lesssim 10^{31}$erg\,s$^{-1}$, typical of a PMS with mass\,$\ge 2 M_\odot$. Our detailed inspection therefore supports a very young, ``pre-stellar core'' evolutionary stage for the cloud. Based on archival Planck and IRAS data, we moreover identify the presence of hot dust, with temperatures $\gtrsim 100$\,K, in addition to the dominant dust component at 14\,K, originating with the associated reflection nebula.Comment: Accepted to A

Mid-Infrared Diagnostics of the Circumnuclear Environments of the Youngest Radio Galaxies

We present a systematic analysis of the mid-infrared (MIR) properties of the youngest radio galaxies, based on low-resolution data provided by the {\it WISE} and {\it IRAS} satellites. We restrict our analysis to sources with available X-ray data that constitute the earliest phase of radio galaxy evolution, i.e. those classified as Gigahertz Peaked Spectrum (GPS) and/or Compact Symmetric Objects (CSOs). In our sample of 29 objects, we find that the host galaxies are predominantly red/yellow ellipticals, with some of them displaying distorted morphology. We find a variety of MIR colors, and observe that the sources in which the MIR emission is dominated by the ISM component uniformly populate the region occupied by galaxies with a wide range of pronounced ($\geq 0.5 M_{\odot}$\,yr$^{-1}$) star formation activity. We compare the MIR color distribution in our sample to that in the general population of local AGN, in the population of evolved FR\,II radio galaxies, and also in the population of radio galaxies with recurrent jet activity. We conclude that the triggering of radio jets in AGN does not differentiate between elliptical hosts with substantially different fractions of young stars; instead there is a relationship between the jet duty cycle and the ongoing star formation. The distribution of the sub-sample of our sources with $z<0.4$ on the low-resolution MIR vs. absorption-corrected X-ray luminosity plane is consistent with the distribution of a sample of local AGN. Finally, we comment on the star formation rates of the two $\gamma$-ray detected sources in our sample, 1146+596 \& 1718--649.Comment: Revised version, accepted by the Astrophysical Journa

Spectroscopic diagnostics of the mid-infrared features of the dark globule DC 314.8-5.1 with the Spitzer Space Telescope

Interstellar matter and star formatio

Data from: Exposure to mitochondrial genotoxins and dopaminergic neurodegeneration in Caenorhabditis elegans

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