Radio-Continuum Study of the Nearby Sculptor Group Galaxies. Part 2: NGC 55 at {\lambda}=20, 13, 6 and 3 cm

A series of new radio-continuum ({\lambda}=20, 13, 6 and 3 cm) mosaic images focused on the NGC55 galactic system were produced using archived observational data from the Australia Telescope Compact Array. These new images are both very sensitive (down to rms=33 {\mu}Jy) and feature high angular resolution (down to <4"). Using these newly created images, 66 previously unidentified discrete sources are identified. Of these sources, 46 were classified as background sources, 11 as HII regions and 6 as supernova remnant candidates. This relatively low number of SNR candidates detected coupled with the low number of large HII regions is consistent with the estimated low star formation rate of the galaxy at 0.06 solar masses per year. Our spectral index map shows that the core of galaxy appears to have a shallow spectral index between {\alpha} = -0.2 and -0.4. This indicates that the core of the galaxy is a region of high thermal radiation output.Comment: 11 pages, 8 figures. Accepted for publication in Astrophysics and Space Scienc

Optical Spectra of SNR Candidates in NGC 300

We present moderate-resolution (<5A) long-slit optical spectra of 51 nebular objects in the nearby Sculptor Group galaxy NGC 300 obtained with the 2.3 meter Advanced Technology Telescope at Siding Spring Observatory, Australia. Adopting the criterion of [SII]/Ha>=0.4 to confirm supernova remnants (SNRs) from optical spectra, we find that of 28 objects previously proposed as SNRs from optical observations, 22 meet this criterion with six showing [SII]/Ha of less than 0.4. Of 27 objects suggested as SNRs from radio data, four are associated with the 28 previously proposed SNRs. Of these four, three (included in the 22 above) meet the criterion. In all, 22 of the 51 nebular objects meet the [SII]/Ha criterion as SNRs while the nature of the remaining 29 objects remains undetermined by these observations.Comment: Accepted for publication in Astrophysics & Space Scienc

Universal DNA methylation age across mammalian tissues

Aging, often considered a result of random cellular damage, can be accurately estimated using DNA methylation profiles, the foundation of pan-tissue epigenetic clocks. Here, we demonstrate the development of universal pan-mammalian clocks, using 11,754 methylation arrays from our Mammalian Methylation Consortium, which encompass 59 tissue types across 185 mammalian species. These predictive models estimate mammalian tissue age with high accuracy (r > 0.96). Age deviations correlate with human mortality risk, mouse somatotropic axis mutations and caloric restriction. We identified specific cytosines with methylation levels that change with age across numerous species. These sites, highly enriched in polycomb repressive complex 2-binding locations, are near genes implicated in mammalian development, cancer, obesity and longevity. Our findings offer new evidence suggesting that aging is evolutionarily conserved and intertwined with developmental processes across all mammals.Publisher PDFPeer reviewe

Universal DNA methylation age across mammalian tissues.

Aging, often considered a result of random cellular damage, can be accurately estimated using DNA methylation profiles, the foundation of pan-tissue epigenetic clocks. Here, we demonstrate the development of universal pan-mammalian clocks, using 11,754 methylation arrays from our Mammalian Methylation Consortium, which encompass 59 tissue types across 185 mammalian species. These predictive models estimate mammalian tissue age with high accuracy (r > 0.96). Age deviations correlate with human mortality risk, mouse somatotropic axis mutations and caloric restriction. We identified specific cytosines with methylation levels that change with age across numerous species. These sites, highly enriched in polycomb repressive complex 2-binding locations, are near genes implicated in mammalian development, cancer, obesity and longevity. Our findings offer new evidence suggesting that aging is evolutionarily conserved and intertwined with developmental processes across all mammals

The discrete X-ray source population of the nearby Sculptor Group Galaxy NGC 55 as revealed by the Chandra X-ray Observatory

We are conducting a multi-wavelength campaign to search for supernova remnants (SNRs) in nearby galaxies. Here we present the analysis of an archival Chandra X-ray Observatory observation of the nearby Sculptor Group galaxy NGC 55. In about 60 kiloseconds of observing time we detected 99 discrete point sources: the limiting unabsorbed luminosity of our observation is approximately 2x10^35 ergs/sec (assuming a distance to the galaxy of 1.8 Mpc). Of these, seven were detected with a sufficient number of counts (200 or more) to permit at least a basic spectral analysis. We find 36 sources in common between the high spatial resolution and high sensitivity Chandra observations and earlier lower resolution and lower sensitivity XMM-Newton X-ray telescope observations, and eight sources in common between Chandra, XMM-Newton and the even lower resolution ROSAT X-ray telescope. We are also analyzing radio and mid-infrared (namely Spitzer) observations of this galaxy to extend the search for resident SNRs and to estimate the star-formation rate of this galaxy. Initial results are presented and discussed. American Astronomical Society, AAS Meeting #221, #249.21

A Chandra observation of the nearby Sculptor Group Sd galaxy NGC 7793

We conducted a Chandra ACIS observation of the nearby Sculptor Group Sd galaxy NGC7793 as part of a multiwavelength study of supernova remnants (SNRs) in nearby galaxies. At the assumed distance to NGC7793 of 3.91Mpc, the limiting unabsorbed luminosity of the detected discrete X-ray sources is Lₓ (0.2-10.0 keV) ≈3 x 10³⁶ erg s⁻¹. A total of 22 discrete sources were detected at the ~3σ level or greater including one ultraluminous X-ray source (ULX). Based on multiwavelength comparisons, we identify X-ray sources coincident with one SNR, the candidate microquasar N7793-S26, one H II region, and two foreground Galactic stars. We also find that the X-ray counterpart to the candidate radio SNR R3 is time variable in its X-ray emission: we therefore rule out the possibility that this source is a single SNR. A marked asymmetry is seen in the distribution of the discrete sources with the majority lying in the eastern half of this galaxy. All of the sources were analyzed using quantiles to estimate spectral properties and spectra of the four brightest sources (including the ULX) were extracted and analyzed. We searched for time variability in the X-ray emission of the detected discrete sources using our measured fluxes along with fluxes measured from prior Einstein and Röntgensatellit observations. From this study, three discrete X-ray sources are established to be significantly variable. A spectral analysis of the galaxy's diffuse emission is characterized by a temperature of kT = 0.19-0.25 keV. The luminosity function of the discrete sources shows a slope with an absolute value of Γ = -0.65 ± 0.11 if we exclude the ULX. If the ULX is included, the luminosity function has a long tail to high Lₓ with a poor-fitting slope of Γ = -0.62 ± 0.2. The ULX-less slope is comparable to the slopes measured for the distributions of NGC6946 and NGC2403 but much shallower than the slopes measured for the distributions of IC 5332 and M83. Lastly, we comment on the multiwavelength properties of the SNR population of NGC7793

Universal DNA methylation age across mammalian tissues

International audienceAging, often considered a result of random cellular damage, can be accurately estimated using DNA methylation profiles, the foundation of pan-tissue epigenetic clocks. Here, we demonstrate the development of universal pan-mammalian clocks, using 11,754 methylation arrays from our Mammalian Methylation Consortium, which encompass 59 tissue types across 185 mammalian species. These predictive models estimate mammalian tissue age with high accuracy (r > 0.96). Age deviations correlate with human mortality risk, mouse somatotropic axis mutations and caloric restriction. We identified specific cytosines with methylation levels that change with age across numerous species. These sites, highly enriched in polycomb repressive complex 2-binding locations, are near genes implicated in mammalian development, cancer, obesity and longevity. Our findings offer new evidence suggesting that aging is evolutionarily conserved and intertwined with developmental processes across all mammals