Search Publications
The extinction law inside the 30 Doradus nebula
Panagia, Nino; De Marchi, Guido
We have studied the interstellar extinction in a field of ∼3 arcmin × 3 arcmin at the core of the 30 Doradus nebula, including the central R 136 cluster, in the Large Magellanic Cloud. Observations at optical and near-infrared wavelengths, obtained with the WFC 3 camera on board the Hubble Space Telescope, show that the stars belonging to the red …
Water and methanol in low-mass protostellar outflows: gas-phase synthesis, ice sputtering and destruction
van Dishoeck, E. F.; Kristensen, L. E.; Mottram, J. C. +2 more
Water in outflows from protostars originates either as a result of gas-phase synthesis from atomic oxygen at T ≳ 200 K, or from sputtered ice mantles containing water ice. We aim to quantify the contribution of the two mechanisms that lead to water in outflows, by comparing observations of gas-phase water to methanol (a grain surface product) towa…
SDSS J143244.91+301435.3: a link between radio-loud narrow-line Seyfert 1 galaxies and compact steep-spectrum radio sources?
Ballo, L.; Dallacasa, D.; Foschini, L. +12 more
We present SDSS J143244.91+301435.3, a new case of a radio-loud narrow-line Seyfert 1 (RL NLS1) with a relatively high radio power (P1.4 GHz = 2.1 × 1025 W Hz-1) and large radio-loudness parameter (R1.4 = 600 ± 100). The radio source is compact with a linear size below ∼1.4 kpc but, in contrast to most o…
Directly imaging damped Lyα galaxies at z > 2 - II. Imaging and spectroscopic observations of 32 quasar fields
Prochaska, J. Xavier; Fumagalli, Michele; Kanekar, Nissim +2 more
Damped Lyα absorbers (DLAs) are a well-studied class of absorption line systems, and yet the properties of their host galaxies remain largely unknown. To investigate the origin of these systems, we have conducted an imaging survey of 32 quasar fields with intervening DLAs between z ∼ 1.9 and 3.8, leveraging a technique that allows us to image gala…
Stellar tidal disruption candidates found by cross-correlating the ROSAT Bright Source Catalogue and XMM-Newton observations
Sazonov, S.; Khabibullin, I.
We performed a systematic search for stellar tidal disruption events (TDE) by looking for X-ray sources that were detected during the ROSAT All Sky Survey and faded by more than an order of magnitude over the next two decades according to XMM-Newton serendipitous observations. Besides a number of highly variable persistent X-ray sources (like acti…
Ultraluminous X-ray sources: a deeper insight into their spectral evolution
Wolter, Anna; Pintore, Fabio; Zampieri, Luca +1 more
We select a sample of nearby ultraluminous X-ray sources with long XMM-Newton observations and analyse all the available XMM-Newton data using both X-ray spectral fitting techniques and hardness-intensity diagrams. The sample includes IC 342 X-1, NGC 5204 X-1, NGC 5408 X-1, Holmberg IX X-1, Holmberg II X-1, NGC 1313 X-1, NGC 1313 X-2 and NGC 253 X…
Very Large Baseline Array observations of Mrk 6: probing the jet-lobe connection
Hardcastle, M. J.; Croston, J. H.; O'Dea, C. P. +5 more
We present the results of high-resolution VLBI (very long baseline interferometry) observations at 1.6 and 4.9 GHz of the radio-loud Seyfert galaxy, Mrk 6. These observations are able to detect a compact radio core in this galaxy for the first time. The core has an inverted spectral index (α ^{1.6}_{4.9} = +1.0 ± 0.2) and a brightness temperature …
Galaxy formation as a cosmological tool - I. The galaxy merger history as a measure of cosmological parameters
Conselice, Christopher J.; Bluck, Asa F. L.; Mortlock, Alice +2 more
As galaxy formation and evolution over long cosmic time-scales depends to a large degree on the structure of the universe, the assembly history of galaxies is potentially a powerful approach for learning about the universe itself. In this paper, we examine the merger history of dark matter haloes based on the Extended Press-Schechter formalism as …
Investigating the sensitivity of observed spectral energy distributions to clumpy torus properties in Seyfert galaxies
Packham, C.; González-Martín, O.; Levenson, N. A. +5 more
We present nuclear spectral energy distributions (SEDs) from 1 to 18 µm of a small sample of nearby, nearly face-on and undisturbed Seyfert galaxies without prominent nuclear dust lanes. These nuclear SEDs probe the central ∼35 pc of the galaxies, on average, and include photometric and spectroscopic infrared (IR) data. We use these SEDs, th…
X-ray time delays in the narrow line Seyfert 1 galaxy PG 1244+026
Done, C.; Vaughan, S.; Alston, W. N.
We analyse the X-ray time-lags in the narrow line Seyfert 1 (NLS1) galaxy PG 1244+026 (MBH ∼ 107 M⊙, L/LEdd ∼ 1). The time delay between the soft (0.3-0.7 keV) and harder (1.2-4.0 keV) variations shows the well-established switch from hard lags at low frequencies to soft lags at high frequencies. The low…