Search Publications
LBT/MODS spectroscopy of globular clusters in the irregular galaxy NGC 4449
Tosi, M.; Cusano, F.; Mignoli, M. +10 more
We present intermediate-resolution (R ∼ 1000) spectra in the ∼3500-10 000 Å range of 14 globular clusters in the Magellanic irregular galaxy NGC 4449 acquired with the Multi-Object Double Spectrograph on the Large Binocular Telescope. We derived Lick indices in the optical and the Ca II triplet index in the near-infrared in order to infer the clus…
K2 observations of the rapidly oscillating Ap star 33 Lib (HD 137949): new frequencies and unique non-linear interactions
Bowman, D. M.; Kurtz, D. W.; Cunha, M. S. +2 more
We present the analysis of K2 short cadence data of the rapidly oscillating Ap (roAp) star, 33 Librae (HD 137949). The precision afforded to the K2 data allow us to identify at least 11 pulsation modes in this star, compared to the three previously reported. Reoccurring separations between these modes lead us to suggest a large frequency separatio…
A distant sample of halo wide binaries from SDSS
Gould, Andrew; Coronado, Johanna; Chanamé, Julio +1 more
Samples of reliably identified halo wide binaries are scarce. If reasonably free from selection effects and with a small degree of contamination by chance alignments, these wide binaries become a powerful dynamical tool, having provided one of the very few experiments capable of constraining the nature of dark matter in the Milky Way halo. Current…
Agnostic stacking of intergalactic doublet absorption: measuring the Ne VIII population
Shull, J. Michael; Danforth, Charles W.; Mathur, Smita +2 more
We present a blind search for doublet intergalactic metal absorption with a method dubbed `agnostic stacking'. Using a forward-modelling framework, we combine this with direct detections in the literature to measure the overall metal population. We apply this novel approach to the search for Ne VIII absorption in a set of 26 high-quality COS spect…
Establishing the spectral turnover of blazar PKS 2155-304 as an outcome of radiative losses
Jeena, K.; Misra, R.; Ravikumar, C. D. +2 more
The broad-band optical/UV and X-ray spectra of blazars have been often modelled as synchrotron component arising from a broken power-law distribution of electrons. A broken power-law distribution is expected, since the high-energy electrons undergo radiative losses effectively. The change in the energy index should then be ≈1 and corresponds to a …
On the nature of the high-energy rollover in 1H 0419-577
Turner, T. J.; Reeves, J. N.; Braito, V. +1 more
A NuSTAR/Swift observation of the luminous Seyfert 1 galaxy 1H 0419-577 taken during 2015 reveals one of the most extreme high-energy cut-offs observed to date from an AGN - an origin due to thermal Comptonization would imply a remarkably low coronal temperature kT ∼ 15 keV. The low-energy peak of the spectrum in the hard X-ray NuSTAR band, which …
Quantifying the abundance of faint, low-redshift satellite galaxies in the COSMOS survey
Rhodes, Jason; Taylor, James E.; Koekemoer, Anton +3 more
Faint dwarf satellite galaxies are important as tracers of small-scale structure, but remain poorly characterized outside the Local Group, due to the difficulty of identifying them consistently at larger distances. We review a recently proposed method for estimating the average satellite population around a given sample of nearby bright galaxies, …
Positron annihilation in the nuclear outflows of the Milky Way
Ruiter, Ashley J.; Panther, Fiona H.; Seitenzahl, Ivo R. +2 more
Observations of soft gamma rays emanating from the Milky Way from SPI/INTEGRAL reveal the annihilation of ∼2 × 1043 positrons every second in the Galactic bulge. The origin of these positrons, which annihilate to produce a prominent emission line centred at 511 keV, has remained mysterious since their discovery almost 50 yr ago. A plaus…
The interaction of the halo around the butterfly planetary nebula NGC 650-1 with the interstellar medium
Guerrero, M. A.; Ramos-Larios, G.; Sabin, L. +7 more
With its bright and wide equatorial waist seen almost edge-on (`the butterfly body') and the faint and broad bipolar extensions (`the butterfly wings'), NGC 650-1 is the archetypical example of bipolar planetary nebula (PN) with butterfly morphology. We present here deep high-resolution broad- and narrow-band optical images that expose the rich an…
Star formation and gas inflows in the OH megamaser galaxy IRAS03056+2034
Robinson, Andrew; Baum, Stefi; Storchi-Bergmann, Thaisa +6 more
We have obtained observations of the OH megamaser galaxy IRAS03056+2034 using the Gemini Multi-Object Spectrograph (GMOS) Integral Field Unit (IFU), Very Large Array (VLA), and Hubble Space Telescope (HST). The HST data reveals spiral arms containing knots of emission associated with star-forming regions. The GMOS-IFU data cover the spectral range…