arXiv subjects

B.

Publications and source records attributed to B..

5 recordsLinked to original sources

arXiv2023

Morphology of star-forming clumps in ram-pressure stripped galaxies as seen by HST

We characterize the morphological properties of a statistically relevant sample of H$\alpha$ and UV young star-forming clumps and optical complexes, observed with the \textit{Hubble Space Telescope} in six galaxies of the GASP sample undergoing ram-pressure stripping. The catalogs comprise 2406 (323 in the tails) H$\alpha$ clumps, 3750 (899) UV clumps and 424 tail optical complexes. About 15-20\% of the clumps and 50\% of the complexes are resolved in size. We find that more than half of the complexes contain no H$\alpha$ clumps, while most of them contain at least one UV clump. The clump number and size increase with the complex size, while the median complex filling factor is larger for UV clumps ($0.27$) than for H$\alpha$ clumps ($0.10$) and does not correlate with almost any morphological property. This suggests that the clumps number and size grow with the complex keeping the filling factor constant. When studying the position of the clumps inside their complexes, H$\alpha$ clumps, and UV clumps to a lesser extent, show a displacement from the complex center of $0.1-1$ kpc and, in $\sim 60$\% of the cases, they are displaced away from the galactic disk. This is in accordance with the fireball configuration, already observed in the tails of stripped galaxies. Finally, the filling factor and the clump radius increase with the distance from the galactic disk, suggesting that the reciprocal displacement of the different stellar generations increases as a consequence of the velocity gradient caused by ram pressure.

astro-ph.GA↗

arXiv2023

Beyond the disk: EUV coronagraphic observations of the Extreme Ultraviolet Imager on board Solar Orbiter

Most observations of the solar corona beyond 2 Rs consist of broadband visible light imagery from coronagraphs. The associated diagnostics mainly consist of kinematics and derivations of the electron number density. While the measurement of the properties of emission lines can provide crucial additional diagnostics of the coronal plasma (temperatures, velocities, abundances, etc.), these observations are comparatively rare. In visible wavelengths, observations at these heights are limited to total eclipses. In the VUV range, very few additional observations have been achieved since the pioneering results of UVCS. One of the objectives of the Full Sun Imager (FSI) channel of the EUI telescope on board the Solar Orbiter mission has been to provide very wide field-of-view EUV diagnostics of the morphology and dynamics of the solar atmosphere in temperature regimes that are typical of the lower transition region and of the corona. FSI carries out observations in two narrowbands of the EUV spectrum centered on 17.4 nm and 30.4 nm that are dominated, respectively, by lines of Fe IX/X (formed in the corona around 1 MK) and by the resonance line of He II (formed around 80 kK in the lower transition region). Unlike previous EUV imagers, FSI includes a moveable occulting disk that can be inserted in the optical path to reduce the amount of instrumental stray light to a minimum. FSI detects signals at 17.4 nm up to the edge of its FOV (7~Rs), which is about twice further than was previously possible. Comparisons with observations by the LASCO and Metis coronagraphs confirm the presence of morphological similarities and differences between the broadband visible light and EUV emissions, as documented on the basis of prior eclipse and space-based observations. The very-wide-field observations of FSI are paving the way for future dedicated instruments.

astro-ph.SR↗

arXiv2017

Half-lives of neutron-rich $^{128-130}$Cd

The $\beta$-decay half-lives of $^{128\text{--}130}$Cd have been measured with the newly commissioned GRIFFIN $\gamma$-ray spectrometer at the TRIUMF-ISAC facility. The time structures of the most intense $\gamma$-rays emitted following the $\beta$-decay were used to determine the half-lives of $^{128}$Cd and $^{130}$Cd to be $T_{1/2}= 246.2(21)$ ms and $T_{1/2}= 126(4)$ ms, respectively. The half-lives of the 3/2$^+$ and 11/2$^-$ states of $^{129}$Cd were measured to be $T_{1/2}(3/2^+)= 157(8)$ ms and $T_{1/2}(11/2^-)= 147(3)$ ms. The half-lives of the Cd isotopes around the $N=82$ shell closure are an important ingredient in astrophysical simulations to derive the magnitude of the second $r$-process abundance peak in the $A\sim130$ region. Our new results are compared with recent literature values and theoretical calculations.

nucl-ex↗

arXiv2010

UWISH2 -- The UKIRT Widefield Infrared Survey for H2

We present the goals and preliminary results of an unbiased, near-infrared, narrow-band imaging survey of the First Galactic Quadrant (10deg<l<65deg ; -1.3deg<b<+1.3deg). This area includes most of the Giant Molecular Clouds and massive star forming regions in the northern hemisphere. The survey is centred on the 1-0S(1) ro-vibrational line of H2, a proven tracer of hot, dense molecular gas in star-forming regions, around evolved stars, and in supernova remnants. The observations complement existing and upcoming photometric surveys (Spitzer-GLIMPSE, UKIDSS-GPS, JCMT-JPS, AKARI, Herschel Hi-GAL, etc.), though we probe a dynamically active component of star formation not covered by these broad-band surveys. Our narrow-band survey is currently more than 60% complete. The median seeing in our images is 0.73arcsec. The images have a 5sigma detection limit of point sources of K=18mag and the surface brightness limit is 10^-19Wm^-2arcsec^-2 when averaged over our typical seeing. Jets and outflows from both low and high mass Young Stellar Objects are revealed, as are new Planetary Nebulae and - via a comparison with earlier K-band observations acquired as part of the UKIDSS GPS - numerous variable stars. With their superior spatial resolution, the UWISH2 data also have the potential to reveal the true nature of many of the Extended Green Objects found in the GLIMPSE survey.

astro-ph.GA↗

arXiv2009

Pulsar Timing with the Parkes Radio Telescope for the Fermi Mission

We report here on two years of timing of 168 pulsars using the Parkes radio telescope. The vast majority of these pulsars have spin-down luminosities in excess of 10^34 erg/s and are prime target candidates to be detected in gamma-rays by the Fermi Gamma-Ray Space Telescope. We provide the ephemerides for the ten pulsars being timed at Parkes which have been detected by Fermi in its first year of operation. These ephemerides, in conjunction with the publicly available photon list, can be used to generate gamma-ray profiles from the Fermi archive. We will make the ephemerides of any pulsars of interest available to the community upon request. In addition to the timing ephemerides, we present the parameters for 14 glitches which have occurred in 13 pulsars, seven of which have no previously known glitch history. The Parkes timing programme, in conjunction with Fermi observations, is expected to continue for at least the next four years.

astro-ph.GA↗