Search Publications
Point spread function tails and the measurements of diffuse stellar halo light around edge-on disc galaxies
de Jong, Roelof S.
Measuring the integrated stellar halo light around galaxies is very challenging. The surface brightness of these haloes is expected to be many magnitudes below dark sky and the central brightness of the galaxy. Here, I show that in some of the recent literature the effect of very extended Point Spread Function (PSF) tails on the measurements of ha…
Properties of the ultraviolet flux of Type Ia supernovae: an analysis with synthetic spectra of SN 2001ep and SN 2001eh
Challis, P.; Kirshner, R. P.; Filippenko, A. V. +7 more
The spectral properties of Type Ia supernovae in the ultraviolet (UV) are investigated using the early-time spectra of SN 2001ep and SN 2001eh obtained using the Hubble Space Telescope. A series of spectral models is computed with a Monte Carlo spectral synthesis code, and the dependence of the UV flux on the elemental abundances and the density g…
Centimetre-wave continuum radiation from the ρ Ophiuchi molecular cloud
Paladini, Roberta; Lim, Tanya; Casassus, Simon +8 more
The ρ Oph molecular cloud is undergoing intermediate-mass star formation. Ultraviolet radiation from its hottest young stars heats and dissociates exposed layers, but does not ionize hydrogen. Only faint radiation from the Rayleigh-Jeans tail of ~10-100 K dust is expected at wavelengths longwards of ~3 mm. Yet cosmic background imager (CBI) observ…
Chandra observation of the edge-on spiral NGC 5775: probing the hot galactic disc/halo connection
Wang, Q. Daniel; Li, Zhiyuan; Li, Jiang-Tao +2 more
We study the edge-on galaxy NGC 5775, utilizing a 58.2 ks Chandra ACIS-S observation together with complementary Hubble Space Telescope (HST) ACS, Spitzer IRAC and other multi-wavelength data sets. This edge-on galaxy, with its disc-wide active star formation, is particularly well suited for studying the disc/halo interaction on subgalactic scales…
Baryonic Tully-Fisher relation for extremely low mass Galaxies
Sharina, M. E.; Begum, Ayesha; Chengalur, Jayaram N. +1 more
We study Tully-Fisher (TF) relations for a sample that combines extremely faint (MB < -14) galaxies along with bright (i.e. ~L*) galaxies. Accurate (~10 per cent) distances, I-band photometry and B - V colours are known for the majority of the galaxies in our sample. The faint galaxies are drawn from the Faint Irregular Ga…
The early expansion of cluster cores
Bastian, N.; Smith, L. J.; Goodwin, S. P. +4 more
The observed properties of young star clusters, such as the core radius and luminosity profile, change rapidly during the early evolution of the clusters. Here we present observations of six young clusters in M51 where we derive their sizes using Hubble Space Telescope (HST) imaging and ages using deep Gemini-North spectroscopy. We find evidence f…
A microlensing study of the accretion disc in the quasar MG 0414+0534
Wyithe, J. S. B.; Bate, N. F.; Floyd, D. J. E. +1 more
Observations of gravitational microlensing in multiply imaged quasars currently provide the only direct probe of quasar emission region structure on submicroarcsecond scales. The analyses of microlensing variability are observationally expensive, requiring long-term monitoring of lensed systems. Here, we demonstrate a technique for constraining th…
The supermassive black hole of FornaxA
Saglia, R. P.; Nowak, N.; Davies, R. I. +3 more
The radio galaxy FornaxA (NGC 1316) is a prominent merger remnant in the outskirts of the Fornax cluster. Its giant radio lobes suggest the presence of a powerful active galactic nuclei (AGN) and thus a central supermassive black hole (SMBH). FornaxA now seems to be in a transition state between active black hole growth and quiescence, as indicate…
On the geometry of broad emission region in quasars
Falomo, R.; Treves, A.; Decarli, R. +1 more
We study the geometry of the Hβ broad emission region by comparing the MBH values derived from Hβ through the virial relation with those obtained from the host galaxy luminosity in a sample of 36 low-redshift (z ~ 0.3) quasars. This comparison lets us infer the geometrical factor f needed to deproject the line-of-sight velocity componen…
The dark matter environment of the Abell 901/902 supercluster: a weak lensing analysis of the HST STAGES survey
Bell, Eric F.; Wisotzki, Lutz; Wolf, Christian +21 more
We present a high-resolution dark matter reconstruction of the z = 0.165 Abell 901/902 supercluster from a weak lensing analysis of the Hubble Space Telescope STAGES survey. We detect the four main structures of the supercluster at high significance, resolving substructure within and between the clusters. We find that the distribution of dark matt…