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The stellar population content of the thick disc and halo of the Milky Way analogue NGC 891
Rejkuba, M.; Mouhcine, M.; Ibata, R.
We present deep VI images obtained with the Advanced Camera for Surveys on board the Hubble Space Telescope, covering three fields in the north-east side of the edge-on disc galaxy NGC 891. The observed fields span a wide range of galactocentric distances along the eastern minor axis, extending from the plane of the disc to 12 kpc, and out to ∼25 …
The nature of late-type spiral galaxies: structural parameters, optical and near-infrared colour profiles and dust extinction
Balcells, Marc; Peletier, Reynier F.; Falcón-Barroso, Jesús +1 more
We analyse V- and H-band surface photometry of a sample of 18 Sb-Sd galaxies. Combining high-resolution Hubble Space Telescope (HST) images with ground-based near-infrared observations, we extract photometric profiles, which cover the whole disc and provide the highest possible resolution. This is the first photometric study of late-type spirals f…
X-ray spectral identification of three candidate quiescent low-mass X-ray binaries in the globular cluster NGC 6304
Pavlov, George G.; Guillot, Sebastien; Zavlin, Vyacheslav E. +3 more
We report the search for low-mass X-ray binaries in quiescence (qLMXBs) in the globular cluster NGC 6304 using XMM-Newton observations. We present the spectral analysis leading to the identification of three candidate qLMXBs within the field of this globular cluster (GC), each consistent with the X-ray spectral properties of previously identified …
On the derivation of dynamical masses of the stellar clusters in the circumnuclear region of NGC2903
Terlevich, Roberto; Terlevich, Elena; Díaz, Ángeles I. +2 more
Gas and star velocity dispersions have been derived for four circumnuclear star-forming regions (CNSFRs) and the nucleus of the spiral galaxy NGC2903 using high-resolution spectroscopy in the blue and far red. Stellar velocity dispersions have been obtained from the CaII triplet lines at λλ8494, 8542, 8662Å, using cross-correlation techniques, whi…
Rings and haloes in the mid-infrared: the planetary nebulae NGC 7354 and NGC 3242
Ramos-Larios, G.; Schröder, K. -P.; Phillips, J. P. +1 more
We present images of the planetary nebulae NGC 7354 and NGC 3242 in four mid-infrared (MIR) photometric bands centred at 3.6, 4.5, 5.8 and 8.0 µm, the results of observations undertaken using the Spitzer Space Telescope. The resulting images show the presence of a halo and rings in NGC 3242, as previously observed through narrow-band imaging…
A spectroscopic survey of EC4, an extended cluster in Andromeda's halo
Tanvir, N.; Mackey, A. D.; Martin, N. F. +8 more
We present a spectroscopic survey of candidate red giant branch stars in the extended star cluster, EC4, discovered in the halo of M31 from our Canada-France-Hawaii Telescope/MegaCam survey, overlapping the tidal streams, Streams`Cp' and `Cr'. These observations used the DEep Imaging Multi-Object Spectrograph mounted on the Keck II telescope to ob…
Obscuring clouds playing hide-and-seek in the active nucleus H0557-385
Bianchi, S.; Guainazzi, M.; Ballo, L. +2 more
This Letter reports on two XMM-Newton observations of the type 1 Seyfert galaxy H0557-385 obtained in 2006, which show the source at an historical low flux state, more than a factor of ~10 lower than a previous XMM-Newton look in 2002. The low flux spectrum presents a strong Fe Kα line associated with a Compton reflection continuum. An additional …
On the role of the post-starburst phase in the buildup of the red sequence of intermediate-redshift clusters
Smail, Ian; Milvang-Jensen, Bo; Zaritsky, Dennis +4 more
We present new deep spectroscopic observations of 0.05-0.5 L* galaxies in one cluster (cl1232.5-1250) drawn from the ESO (European Southern Observatory) Distant Cluster Survey (EDisCS) sample, at z = 0.54. The new data extend the spectroscopy already available for this cluster by about 1 mag. The cluster has a large fraction of passive …
Hemispheric variation of coronal mass ejections in cycle 23
Gao, Peng-Xin; Li, Ke-Jun; Shi, Xiang-Jun
In this paper, we analyse the behaviour of the activity of coronal mass ejection (CME) observed by the Large Angle and Spectrometric Coronagraph Experiment on board the Solar and Heliospheric Observatory (SOHO/LASCO) in cycle 23 from 1997 to 2007 separately for the Northern and Southern hemispheres. The results show the following. (1) At all and l…
Monte Carlo simulations of the broad-band X-ray continuum of SS433
Postnov, K. A.; Cherepashchuk, A. M.; Bisnovatyi-Kogan, G. S. +1 more
We develop a Monte Carlo technique based on L.B. Lucy's indivisible photon packets method to calculate X-ray continuum spectra of Comptonized thermal plasma in arbitrary geometry and apply it to describe the broad-band X-ray continuum of the galactic superaccreting microquasar SS433 observed by INTEGRAL. A physical model of the X-ray emitting regi…