Space Telescope (space + telescope)

Distribution by Scientific Domains

Kinds of Space Telescope

  • hubble space telescope
  • spitzer space telescope

  • Terms modified by Space Telescope

  • space telescope observation

  • Selected Abstracts

    New multiply-lensed galaxies identified in ACS/NIC3 observations of Cl0024+1654 using an improved mass model

    Adi Zitrin
    ABSTRACT We present an improved strong-lensing analysis of Cl0024+1654 (z= 0.39) using deep Hubble Space Telescope (HST)/Advanced Camera for Surveys (ACS)/NIC3 images, based on 33 multiply-lensed images of 11 background galaxies. These are found with a model that assumes mass approximately traces light, with a low-order expansion to allow for flexibility on large scales. The model is constrained initially by the well-known five-image system (z= 1.675) and refined as new multiply-lensed systems are identified using the model. Photometric redshifts of these new systems are then used to constrain better the mass profile by adopting the standard cosmological relation between redshift and lensing distance. Our model requires only six free parameters to describe well all positional and redshift data. The resulting inner mass profile has a slope of d log M/d log r,,0.55, consistent with new weak-lensing measurements where the data overlap, at r, 200 kpc/h70. The combined profile is well fitted by a high-concentration Navarro, Frenk & White (NFW) mass profile, Cvir, 8.6 1.6, similar to other well-studied clusters, but larger than predicted with standard , cold dark matter (,CDM). A well-defined radial critical curve is generated by the model and is clearly observed at r, 12 arcsec, outlined by elongated images pointing towards the centre of mass. The relative fluxes of the multiply-lensed images are found to agree well with the modelled magnifications, providing an independent consistency check. [source]

    The stellar population content of the thick disc and halo of the Milky Way analogue NGC 891

    M. Rejkuba
    ABSTRACT 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 kpc along the major axis. The photometry of individual stars reaches ,2.5 mag below the tip of the red giant branch. We use the astrophotometric catalogue to probe the stellar content and metallicity distribution across the thick disc and spheroid of NGC 891. The colour,magnitude diagrams of thick disc and spheroid population are dominated by old red giant branch stars with a wide range of metallicities, from the sparsely populated metal-poor tail at [Fe/H],,2.4 dex, up to about half-solar metallicity. The peak of the metallicity distribution function of the thick disc is at ,0.9 dex. The inner parts of the thick disc, within ,14 kpc along the major axis show no vertical colour/metallicity gradient. In the outer parts, a mild vertical gradient of ,(V,I)0/,|Z| = 0.1 0.05 kpc,1 or less than 0.1 dex kpc,1 is detected, with bluer colours or more metal-poor stars at larger distances from the plane. This gradient is, however, accounted for by the mixing with the metal-poor halo stars. No metallicity gradient along the major axis is present for thick-disc stars, but strong variations of about 0.35 dex around the mean of [Fe/H]=,1.13 dex are found. The properties of the asymmetric metallicity distribution functions of the thick-disc stars show no significant changes in both the radial and the vertical directions. The stellar populations situated within the solar-cylinder-like distances show strikingly different properties from those of the Galaxy populating similar distances. This suggests that the accretion histories of both galaxies have been different. The spheroid population, composed of the inner spheroid and the halo, shows remarkably uniform stellar population properties. The median metallicity of the halo stellar population shows a shallow gradient from about ,1.15 dex in the inner parts to ,1.27 dex at 24 kpc distance from the centre, corresponding to ,13reff. Similar to the thick-disc stars, large variations around the mean relation are present. [source]

    Evolution in the discs and bulges of group galaxies since z= 0.4

    Sean L. McGee
    ABSTRACT We present quantitative morphology measurements of a sample of optically selected group galaxies at 0.3 < z < 0.55 using the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) and the gim2d surface brightness fitting software package. The group sample is derived from the Canadian Network for Observational Cosmology Field Galaxy Redshift Survey (CNOC2) and follow-up Magellan spectroscopy. We compare these measurements to a similarly selected group sample from the Millennium Galaxy Catalogue (MGC) at 0.05 < z < 0.12. We find that, at both epochs, the group and field fractional bulge luminosity (B/T) distributions differ significantly, with the dominant difference being a deficit of disc-dominated (B/T < 0.2) galaxies in the group samples. At fixed luminosity, z= 0.4 groups have ,5.5 2 per cent fewer disc-dominated galaxies than the field, while by z= 0.1 this difference has increased to ,19 6 per cent. Despite the morphological evolution we see no evidence that the group environment is actively perturbing or otherwise affecting the entire existing disc population. At both redshifts, the discs of group galaxies have similar scaling relations and show similar median asymmetries as the discs of field galaxies. We do find evidence that the fraction of highly asymmetric, bulge-dominated galaxies is 6 3 per cent higher in groups than in the field, suggesting there may be enhanced merging in group environments. We replicate our group samples at z= 0.4 and 0 using the semi-analytic galaxy catalogues of Bower et al. This model accurately reproduces the B/T distributions of the group and field at z= 0.1. However, the model does not reproduce our finding that the deficit of discs in groups has increased significantly since z= 0.4. [source]

    A shallow though extensive H2 2.122-,m imaging survey of Taurus,Auriga,Perseus , I. NGC 1333, L1455, L1448 and B1

    C. J. Davis
    ABSTRACT We discuss wide-field near-infrared (near-IR) imaging of the NGC 1333, L1448, L1455 and B1 star-forming regions in Perseus. The observations have been extracted from a much larger narrow-band imaging survey of the Taurus,Auriga,Perseus complex. These H2 2.122-,m observations are complemented by broad-band K imaging, mid-IR imaging and photometry from the Spitzer Space Telescope, and published submillimetre CO J= 3,2 maps of high-velocity molecular outflows. We detect and label 85 H2 features and associate these with 26 molecular outflows. Three are parsec-scale flows, with a mean flow lobe length exceeding 11.5 arcmin. 37 (44 per cent) of the detected H2 features are associated with a known Herbig,Haro object, while 72 (46 per cent) of catalogued HH objects are detected in H2 emission. Embedded Spitzer sources are identified for all but two of the 26 molecular outflows. These candidate outflow sources all have high near-to-mid-IR spectral indices (mean value of ,, 1.4) as well as red IRAC 3.6,4.5 ,m and IRAC/MIPS 4.5,24.0 ,m colours: 80 per cent have [3.6],[4.5] > 1.0 and [4.5],[24] > 1.5. These criteria , high , and red [4.5],[24] and [3.6],[4.5] colours , are powerful discriminants when searching for molecular outflow sources. However, we find no correlation between , and flow length or opening angle, and the outflows appear randomly orientated in each region. The more massive clouds are associated with a greater number of outflows, which suggests that the star formation efficiency is roughly the same in each region. [source]

    Spitzer observations of M83 and the hot star, H ii region connection

    Robert H. Rubin
    ABSTRACT We have undertaken a programme to observe emission lines of [S iv] 10.51, [Ne ii] 12.81, [Ne iii] 15.56, and [S iii] 18.71 ,m in a number of extragalactic H ii regions with the Spitzer Space Telescope. Here we report our results for the nearly face-on spiral galaxy M83. A subsequent paper will present our data and analysis for another substantially face-on spiral galaxy M33. The nebulae selected cover a wide range of galactocentric radii (RG). The observations were made with the infrared spectrograph in the short wavelength, high dispersion configuration. The above set of four lines is observed cospatially, thus permitting a reliable comparison of the fluxes. From the measured fluxes, we determine the ionic abundance ratios including Ne++/Ne+, S3+/S++ and S++/Ne+ and find that there is a correlation of increasingly higher ionization with larger RG. By sampling the dominant ionization states of Ne and S for H ii regions, we can approximate the Ne/S ratio by (Ne++ Ne++)/(S+++ S3+). Our findings of ratios that significantly exceed the benchmark Orion Nebula value, as well as a decrease in this ratio with increasing RG, are more likely due to other effects than a true gradient in Ne/S. Two effects that will tend to lower these high estimates and to flatten the gradient are first, the method does not account for the presence of S+ and second, S but not Ne is incorporated into grains. Both Ne and S are primary elements produced in ,-chain reactions, following C and O burning in stars, making their yields depend very little on the stellar metallicity. Thus, it is expected that Ne/S remains relatively constant throughout a galaxy. We stress that this type of observation and method of analysis does have the potential for accurate measurements of Ne/S, particularly for H ii regions that have lower metallicity and higher ionization than those here, such as those in M33. Our observations may also be used to test the predicted ionizing spectral energy distribution (SED) of various stellar atmosphere models. We compare the ratio of fractional ionizations ,Ne++,/,S++, and ,Ne++,/,S3+, versus ,S3+,/,S++, with predictions made from our photoionization models using several of the state-of-the-art stellar atmosphere model grids. The overall best fit appears to be the nebular models using the supergiant stellar atmosphere models of Pauldrach, Hoffmann & Lennon and Sternberg, Hoffmann & Pauldrach. This result is not sensitive to the electron density and temperature range expected for these M83 nebulae. Considerable computational effort has gone into the comparison between data and models, although not all parameter studies have yet been performed on an ultimate level (e.g. in the present paper the stellar atmosphere model abundances have been fixed to solar values). A future paper, with the benefit of more observational data, will continue these studies to further discriminate how the ionic ratios depend on the SED and the other nebular parameters. [source]

    Structural parameters of Mayall II = G1 in M31

    J. Ma
    ABSTRACT Mayall II = G1 is one of the most luminous globular clusters (GCs) known in M31. New deep, high-resolution observations with the Advanced Camera for Surveys on the Hubble Space Telescope are used to provide accurate photometric data to the smallest radii yet. In particular, we present the precise variation of ellipticity and position angle, and of surface brightness for the core of the object. Based on these accurate photometric data, we redetermine the structural parameters of G1 by fitting a single-mass isotropic King model. We derive a core radius, rc= 0.21 0.01 arcsec (= 0.78 0.04 pc), a tidal radius, rt= 21.8 1.1 arcsec (= 80.7 3.9 pc), and a concentration index c= log (rt/rc) = 2.01 0.02. The central surface brightness is 13.510 mag arcsec,2. We also calculate the half-light radius, at rh= 1.73 0.07 arcsec (= 6.5 0.3 pc). The results show that, within 10 core radii, a King model fits the surface brightness distribution well. We find that this object falls in the same region of the MV versus log Rh diagram as , Centauri, M54 and NGC 2419 in the Milky Way. All three of these objects have been claimed to be the stripped cores of now defunct dwarf galaxies. We discuss in detail whether GCs, stripped cores of dwarf spheroidals and normal dwarf galaxies form a continuous distribution in the MV versus log Rh plane, or if GCs and dwarf spheroidals constitute distinct classes of objects; we present arguments in favour of this latter view. [source]

    Gravitational lensing by cosmic strings: what we learn from the CSL-1 case

    M. V. Sazhin
    ABSTRACT Cosmic strings were postulated by Kibble in 1976 and, from a theoretical point of view, their existence finds support in modern superstring theories, both in compactification models and in theories with extended additional dimensions. Their eventual discovery would lead to significant advances in both cosmology and fundamental physics. One of the most effective ways to detect cosmic strings is through their lensing signatures which appear to be significantly different from those introduced by standard lenses (i.e. compact clumps of matter). In 2003, the discovery of the peculiar object CSL-1 raised the interest of the physics community since its morphology and spectral features strongly argued in favour of it being the first case of gravitational lensing by a cosmic string. In this paper we provide a detailed description of the expected observational effects of a cosmic string and show, by means of simulations, the lensing signatures produced on background galaxies. While high angular resolution images obtained with Hubble Space Telescope, revealed that CSL-1 is a pair of interacting ellipticals at redshift 0.46, it represents a useful lesson to plan future surveys. [source]

    A highly obscured and strongly clustered galaxy population discovered with the Spitzer Space Telescope

    M. Magliocchetti
    ABSTRACT The ,800 optically unseen (R > 25.5) 24-,m selected sources in the complete Spitzer First Look Survey sample with F24 ,m, 0.35 mJy are found to be very strongly clustered. If, as indicated by several lines of circumstantial evidence, they are ultraluminous far-infrared galaxies at z, 1.6,2.7, the amplitude of their spatial correlation function is very high. The associated comoving clustering length is estimated to be r0= 14.0+2.1,2.4 Mpc, value which puts these sources amongst the most strongly clustered populations of our known Universe. Their 8,24 ,m colours suggest that the active galactic nucleus contribution dominates above F24 ,m, 0.8 mJy, consistent with earlier analyses. The properties of these objects (number counts, redshift distribution, clustering amplitude) are fully consistent with those of proto-spheroidal galaxies in the process of forming most of their stars and of growing their active nucleus, as described by the Granato et al. model. In particular, the inferred space density of such galaxies at z, 2 is much higher than what is expected from most semi-analytic models. Matches of the observed projected correlation function w(,) with models derived within the so-called halo occupation scenario show that these sources have to be hosted by haloes more massive than ,1013.4 M,. This value is significantly higher than that for the typical galactic haloes hosting massive elliptical galaxies, suggesting a duration of the starburst phase of massive high-redshift dusty galaxies of TB, 0.5 Gyr. [source]

    A census of young stellar populations in the warm ULIRG PKS 1345+12

    J. Rodrguez Zaurn
    ABSTRACT We present a detailed investigation of the young stellar populations (YSP) in the radio-loud ultraluminous infrared galaxy (ULIRG), PKS 1345+12 (z= 0.12), based on high-resolution Hubble Space Telescope (HST) imaging and long-slit spectra taken with the William Herschel Telescope (WHT) at La Palma. While the images clearly show bright knots suggestive of super star clusters (SSCs), the spectra reveal the presence of YSP in the diffuse light across the full extent of the halo of the merging double nucleus system. Spectral synthesis modelling has been used to estimate the ages of the YSP for both the SSC and the diffuse light sampled by the spectra. For the SSC, we find ages tSSC < 6 Myr with reddenings 0.2 < E(B,V) < 0.5 and masses 106 < MYSPSSC < 107 M,. In the region to the south of the western nucleus that contains the SSC our modelling of the spectrum of the diffuse light is also consistent with a relatively young age for the YSP (,5 Myr), although older YSP ages cannot be ruled out. However, in other regions of the galaxy we find that the spectra of the diffuse light component can only be modelled with a relatively old post-starburst YSP (0.04,1.0 Gyr) or with a disc galaxy template spectrum. The results demonstrate the importance of accounting for reddening in photometric studies of SSC and highlight the dangers of focusing on the highest surface brightness regions when trying to obtain a general impression of the star formation activity in the host galaxies of ULIRGs. The case of PKS 1345+12 provides clear evidence that the star formation histories of the YSP in ULIRGs are complex. While the SSC represent the vigorous phase of star formation associated with the final stages of the merger, the YSP in the diffuse light are likely to represent star formation in one or more of the merging galaxies at an earlier stage or prior to the start of the merger. Intriguingly, our long-slit spectra show line splitting at the locations of the SSC, indicating that they are moving at up to 450 km s,1 with respect to the local ambient gas. Given their kinematics, it is plausible that the SSCs have been formed either in fast moving gas streams/tidal tails that are falling back into the nuclear regions as part of the merger process or as a consequence of jet-induced star formation linked to the extended, diffuse radio emission detected in the halo of the galaxy. [source]

    The stellar mass density at z, 6 from Spitzer imaging of i,-drop galaxies

    Laurence P. Eyles
    ABSTRACT We measure the ages, stellar masses, and star formation histories of z, 6 galaxies, observed within 1 Gyr of the big bang. We use imaging from the Hubble Space Telescope (HST) and the Spitzer Space Telescope from the public ,Great Observatories Origins Deep Survey' (GOODS), coupled with ground-based near-infrared imaging, to measure their spectral energy distributions (SEDs) from 0.8,5 ,m, spanning the rest-frame ultraviolet (UV) and optical. From our sample of ,50 ,i,-drop' Lyman-break star-forming galaxies in GOODS-South with z,AB < 27, we focus on ,30 with reliable photometric or spectroscopic redshifts. Half of these are confused with foreground sources at Spitzer resolution, but from the 16 with clean photometry we find that a surprisingly large fraction (40 per cent) have evidence for substantial Balmer/4000- spectral breaks. This indicates the presence of old underlying stellar populations that dominate the stellar masses. For these objects, we find ages of ,200,700 Myr, implying formation redshifts of 7 ,zf, 18, and large stellar masses in the range ,1,3 1010 M,. Analysis of seven i,-drops that are undetected at 3.6 ,m indicates that these are younger, considerably less massive systems. We calculate that emission line contamination should not severely affect our photometry or derived results. Using SED fits out to 8 ,m, we find little evidence for substantial intrinsic dust reddening in our sources. We use our individual galaxy results to obtain an estimate of the global stellar mass density at z, 6. Correcting for incompleteness in our sample, we find the z, 6 comoving stellar mass density to be 2.5 106 M, Mpc,3. This is a lower limit, as post-starburst and dust-obscured objects, and also galaxies below our selection thresholds, are not accounted for. From our results, we are able to explore the star formation histories of our selected galaxies, and we suggest that the past global star formation rate may have been much higher than that observed at the z, 6 epoch. The associated UV flux we infer at z > 7 could have played a major role in reionizing the Universe. [source]

    Near-infrared polarimetry and modelling of the dusty young planetary nebula IRAS 19306+1407

    K. T. E. Lowe
    ABSTRACT We present near-infrared polarimetric images of the dusty circumstellar envelope (CSE) of IRAS 19306+1407, acquired at the United Kingdom Infrared Telescope (UKIRT) using the UKIRT 1,5 ,m Imager Spectrometer (UIST) in conjunction with the half-waveplate module IRPOL2. We present additional 450- and 850-,m photometry data obtained with the Submillimetre Common-User Bolometer Array (SCUBA) at the James Clerk Maxwell Telescope (JCMT), as well as archived Hubble Space Telescope (HST) F606W - and F814W -filter images. The CSE structure in polarized flux at J and K bands shows an elongation north of north-east and south of south-west with two bright scattering shoulders north-west and south-east. These features are not perpendicular to each other and could signify a recent ,twist' in the outflow axis. We model the CSE using an axisymmetric light scattering (als) code to investigate the polarization produced by the CSE, and an axisymmetric radiation transport (dart) code to fit the spectral energy distribution. A good fit was achieved with the als and dart models using silicate grains, 0.1,0.4 ,m with a power-law size distribution of a,3.5, and an axisymmetric shell geometry with an equator-to-pole ratio of 7:1. The spectral type of the central star is determined to be B1i supporting previous suggestions that the object is an early planetary nebula. We have constrained the CSE and interstellar extinction as 2.0 and 4.2 mag, respectively, and have estimated a distance of 2.7 kpc. At this distance, the stellar luminosity is ,4500 L, and the mass of the CSE is ,0.2 M,. We also determine that the mass loss lasted for ,5300 yr with a mass-loss rate of ,3.4 10,5 M, yr,1. [source]

    Seasonal evolution of Titan's dark polar hood: midsummer disappearance observed by the Hubble Space Telescope

    Ralph D. Lorenz
    ABSTRACT Titan, Saturn's largest moon, has a dense organic-laden atmosphere that displays dramatic seasonal variations in composition and appearance. Here we document the evolution of the dark polar hood, first seen in 1980 by Voyager 1 around the north pole, and report quantitative measurements of the hood's disappearance from the south pole in 2002,2003 using previously unpublished observations with the Hubble Space Telescope Advanced Camera for Surveys (HST/ACS). These data support a model of the hood as a transient structure associated with downwelling during polar winter. [source]

    The possible detection of high-redshift Type II QSOs in deep fields

    Avery Meiksin
    ABSTRACT The colours of high-redshift Type II quasi-stellar objects (QSOs) are synthesized from observations of moderate-redshift systems. It is shown that Type II QSOs are comparable to starbursts at matching the colours of z850 -dropouts and i775 -drops in the Hubble UltraDeep Field, and more naturally account for the bluest objects detected. Type II QSOs may also account for some of the i775 -drops detected in the Great Observatories Origins Deep Survey (GOODS) fields. It is shown that by combining imaging data from the Hubble Space Telescope and the James Webb Space Telescope, it will be possible to clearly separate Type II QSOs from Type I QSOs and starbursts based on their colours. Similarly, it is shown that the United Kingdom Infrared Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS) ZYJ filters may be used to discriminate high-redshift Type II QSOs from other objects. If Type II QSOs are prevalent at high redshifts, then active galactic nuclei (AGNs) may be major contributors to the re-ionization of the intergalactic medium. [source]

    Astrophysical laser operating in the O i 8446- line in the Weigelt blobs of , Carinae

    S. Johansson
    ABSTRACT Within the framework of a simple model of photophysical processes in the Weigelt blobs in the vicinity of the luminous blue variable (LBV) star , Carinae, we explain the presence of the fluorescent ,O i, 8446- and forbidden [O i] 6300- lines as well as the absence of the allowed O i 7774- line in spectra recorded with the Hubble Space Telescope (HST)/STIS instrument (Gull et al.). From atomic data and estimated stellar parameters we demonstrate that there is a population inversion and stimulated emission in the 3p 3P,3s 3S transition ,8446 due to photoexcitation by accidental resonance (PAR) by H Ly, radiation. [source]

    Infrared mergers and infrared quasi-stellar objects with galactic winds , III.

    Mrk 231: an exploding young quasi-stellar object with composite outflow/broad absorption lines (and multiple expanding superbubbles)
    ABSTRACT We present a study of outflow (OF) and broad absorption line (BAL) systems in Mrk 231, and in similar infrared (IR) quasi-stellar objects (QSOs). This study is based mainly on one-dimensional and two-dimensional spectroscopy (obtained at La Palma/William Herschel Telescope, Hubble Space Telescope, International Ultraviolet Explorer, European Southern Observatory/New Technology Telescope, Kitt Peak National Observatory, Apache Point Observatory and Complejo Astronomico El Leoncito observatories) plus Hubble Space Telescope images. For Mrk 231, we report evidence that the extreme nuclear OF process has at least three main components on different scales, which are probably associated with: (i) the radio jet, at parsec scale; (ii) the extreme starburst at parsec and kiloparsec scale. This OF has generated at least four concentric expanding superbubbles and the BAL systems. Specifically, inside and very close to the nucleus the two-dimensional spectra show the presence of an OF emission bump in the blend H,+[N ii], with a peak at the same velocity of the main BAL-I system (VEjection BAL-I,,4700 km s,1). This bump was more clearly detected in the area located at 0.6,1.5 arcsec (490,1220 pc), to the south-west of the nucleus core, showing a strong and broad peak. In addition, in the same direction [at position angle (PA) ,,120, i.e. close to the PA of the small-scale radio jet] at 1.7,2.5 arcsec, we also detected multiple narrow emission-line components, with ,greatly' enhanced [N ii]/H, ratio (very similar to the spectra of jets bow shocks). These results suggest that the BAL-I system is generated in OF clouds associated with the parsec-scale jet. The Hubble Space Telescope images show four (or possibly five) nuclear superbubbles or shells with radii r, 2.9, 1.5, 1.0, 0.6 and 0.2 kpc. For these bubbles, the two-dimensional H, velocity field map and two-dimensional spectra show the following. (i) At the border of the more extended bubble (S1), a clear expansion of the shell with blueshifted velocities (with circular shape and at a radius r, 5.0 arcsec). This bubble shows a rupture arc , to the south , suggesting that the bubble is in the blowout phase. The axis of this rupture or ejection (at PA , 00) is coincident with the axis of the intermediate and large-scale structures detected at radio wavelengths. (ii) In addition, in the three more external bubbles (S1, S2, S3), the two-dimensional William Herschel Telescope spectra show multiple emission-line components with OF velocities, of ,VOF Bubble, S1, S2 and S3 =[,(650 , 420) 30], [,500 30] and [,230 30] km s,1. (iii) In the whole circumnuclear region (1.8 < r < 5 arcsec), the [N ii]/H, and [S ii]/H, narrow emission-line ratios show high values (>0.8), which are consistent with low-ionization nuclear emission-line region/OF processes associated with fast velocity shocks. Therefore, we suggest that these giant bubbles are associated with the large-scale nuclear OF component, which is generated , at least in part , by the extreme nuclear starburst: giant supernova/hypernova explosions. The variability of the short-lived BAL-III Na i D system was studied, covering almost all the period in which this system appeared (between ,1984 and 2004). We have found that the BAL-III light curve is clearly asymmetric with a steep increase, a clear maximum and an exponential fall (similar to the shape of a supernova light curve). The origin of this BAL-III system is discussed, mainly in the framework of an extreme explosive event, probably associated with giant supernova/hypernova explosions. Finally, the IR colour diagram and the ultraviolet BAL systems of IR + GW/OF + Fe ii QSOs are analysed. This study shows two new BAL IR QSOs and suggests/confirms that these objects could be nearby young BAL QSOs, similar to those detected recently at z, 6.0. We propose that the phase of young QSOs is associated with accretion of a large amount of gas (by the supermassive black hole) + extreme starbursts + extreme composite OFs/BALs. [source]

    The host galaxies of Type Ia supernovae at z= 0.6

    D. Farrah
    ABSTRACT We examine the host galaxies of high-redshift Type Ia supernovae (SNe Ia) using archival I - and R -band data from the Hubble Space Telescope. The SNe Ia host galaxies show a wide variety of morphologies, including undisturbed ellipticals, spirals and disturbed systems. SNe Ia are also found over a wide range of projected distances from the host galaxy centres, ranging from 3 kpc to ,30 kpc. For a sample of 22 SNe Ia at ,z,= 0.6, ,70 per cent are found in spiral galaxies and ,30 per cent are found in elliptical systems, similar to the proportions observed locally. Including data from Ellis & Sullivan (2001), we find no significant difference in the average light-curve shape-corrected MBpeak for high- z SNe Ia between spirals and ellipticals. These results are consistent with predictions based on the locally derived understanding of SNe Ia physics and the influence of progenitor mass and metallicity. We also construct colour maps for two host galaxies and find that both show a non-uniform colour structure with typical variations of rest-frame B,V, 0.5. This is most plausibly attributed to the presence of, and variation in, dust extinction in these galaxies. Moreover, we find no evidence that the SNe Ia are preferentially found in outer regions (> 10 kpc) of the host galaxies where extinction would be low. This suggests that the range of host galaxy extinctions of SNe Ia at z, 0.6 should be comparable to those of local SNe Ia. Although observational bias cannot be completely ruled out, this appears to be in conflict with the finding of low extinction for SNe Ia found in the high- z supernova search studies. [source]

    The space density of low-redshift active galactic nuclei

    D. Londish
    We present a new determination of the optical luminosity function (OLF) of active galactic nuclei (AGN) at low redshifts (z<0.15) based on Hubble Space Telescope (HST) observations of X-ray-selected AGN. The HST observations have allowed us to derive a true nuclear luminosity function for these AGN. The resulting OLF illustrates a two power-law form similar to that derived for quasi-stellar objects (QSOs) at higher redshifts. At bright magnitudes, MB<,20, the OLF derived here exhibits good agreement with that derived from the Hamburg/European Southern Observatory (ESO) QSO survey. However, the single power-law form for the OLF derived from the Hamburg/ESO survey is strongly ruled out by our data at MB>,20. Although the estimate of the OLF is best fitted by a power-law slope at MB<,20.5 that is flatter than the slope of the OLF derived at z>0.35, the binned estimate of the low-redshift OLF is still consistent with an extrapolation of the z>0.35 OLF based on pure luminosity evolution. [source]

    Deep spectroscopy of distant 3CR radio galaxies: the data

    P. N. Best
    Deep long-slit spectroscopic data are presented for a sample of 14 3CR radio galaxies at redshift z,1, previously studied in detail using the Hubble Space Telescope, the Very Large Array, and the UK Infrared Telescope (UKIRT). Analysis of the [O ii] 3727 emission-line structures at ,5 spectral resolution is carried out to derive the kinematic properties of the emission-line gas. In line with previous lower resolution studies, a wide variety of kinematics are seen, from gas consistent with a mean rotational motion through to complex structures with velocity dispersions exceeding 1000 km s ,1. The data confirm the presence of a high-velocity gas component in 3C 265 and detached emission-line systems in 3C 356 and 3C 441, and show for the first time that the emission-line gas in the central regions of 3C 324 is composed of two kinematically distinct components. Emission-line fluxes and the colour of the continuum emission are determined down to unprecedentedly low observed wavelengths, ,<3500 , sufficiently short that any contribution of an evolved stellar population is negligible. An accompanying paper investigates the variation in the emission-line ratios and velocity structures within the sample, and draws conclusions as to the origin of the ionization and kinematics of these galaxies. [source]

    MAGIC J0616+225 as delayed TeV emission of cosmic rays diffusing from the supernova remnant IC 443

    Diego F. Torres
    ABSTRACT We present a theoretical model that explains the high-energy phenomenology of the neighbourhood of the supernova remnant IC 443, as observed with the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescope and the Energetic Gamma-Ray Experiment Telescope (EGRET). We interpret MAGIC J0616+225 as delayed TeV emission of cosmic rays diffusing from IC 443 and interacting with a known cloud located at a distance of about 20 pc in the foreground of the remnant. This scenario naturally explains the displacement between EGRET and MAGIC sources, their fluxes, and their spectra. We compare this model with others recently presented, and discuss how it can be tested with observations by the Gamma-ray Large Area Space Telescope. [source]

    Prospects of stellar abundance studies from near-IR spectra observed with the E-ELT

    N. Ryde
    Abstract In 2006 ESO Council authorized a Phase B study of a European AO-telescope with a 42 m segmented primary with a 5-mirror design, the E-ELT. Several reports and working groups have already presented science cases for an E-ELT, specifically exploiting the new capabilities of such a large telescope. One of the aims of the design has been to find a balance in the performances between an E-ELT and the James Webb Space Telescope, JWST. Apart from the larger photon-collecting area, the strengths of the former is the higher attainable spatial and spectral resolutions. The E-ELT AO system will have an optimal performance in the near-IR, which makes it specially advantageous. High-resolution spectroscopy in the near-infrared has, however, not been discussed much. This paper aims at filling that gap, by specifically discussing spectroscopy of stellar (mainly red giant), photospheric abundances. Based on studies in the literature of stellar abundances, at the needed medium to high spectral resolutions in the near-infrared (0.8,2.4 ,m), I will try to extrapolate published results to the performance of the E-ELT and explore what could be done at the E-ELT in this field. A discussion on what instrument characteristics that would be needed for stellar abundance analyses in the near-IR will be given ( 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Productivity and impact of astronomical facilities: A recent sample

    V. Trimble
    Abstract The papers published in 11 key astronomical journals in 2008, and a year of citations to those from the first half of the year, have been associated with the telescopes, satellites, and so forth where the data were gathered using a form of fractional counting. Some numbers are also given by journal, by subfield, and by wavelength band. The largest numbers of papers, and generally also quite highly cited ones, in their respective wavelength bands come from the Very Large Array, the Hubble Space Telescope, the Sloan Digital Sky Survey, the Spitzer Space Telescope, and the Chandra X-ray Telescope. Optical astronomy is still the largest sector; and papers about cosmology and exoplanets are cited more often than papers about binary stars and planetary nebulae. The authors conclude that it is of equal importance to recognize (a) that a very large number of papers also come from less famous facilities, (b) that a very large fraction of papers (and their authors) are concerned with the less highly-cited topics, (c) that many facilities are quite slow in achieving their eventual level of influence, and (d) that one really needs at least three years of citation data, not just one or two, to provide a fair picture of what is going on ( 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    The evolution of cluster dwarfs

    D. Harsono
    Abstract We summarize the results from analyzing six clusters of galaxies at 0.14 < z < 0.40 observed with the Hubble Space Telescope Advanced Camera for Surveys. We derive deep composite luminosity functions in B, g, V, r, i, and z down to absolute magnitude of , ,14 + 5 log h mag. The luminosity functions are fitted by a single Schechter function with MBgVriz * = ,19.8, ,20.9, ,21.9, ,22.0, ,21.7, and ,22.3 mag, and , , ,1.3 for all bands. The data suggests red sequence dominates the luminosity function down to ,6 mag below L*, the dwarf spheroidals regime. Hence, at least at z 0.3, the red sequence is well established and galaxies down to dwarf spheroidals are assembled within these clusters. We do not detect the faint-end upturn (M > ,16) that is observed in lower redshift clusters. If this is real, the faint-end population has originated since z = 0.3 ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    HST experience in data management

    R. Albrecht
    Abstract The data generated by the Hubble Space Telescope pose a series of special requirements for the analysis process. The Hubble Space Telescope (HST) is being operated in a semi-autonomous, pre-programmed manner, executing a queue of observing requests. Calibration is being done "institutionally", i.e. not in response to individual observing programs, but in the same manner for all users. Data products are being generated for the observers, and they are ingested in the HST science data archives, to make them available for further exploitation through the Virtual Observatory. Added value products can be generated by combining data from different programs. Interactive analysis tools are being supplied to support users in the optimum exploitation of the data. ( 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Two observatories, three dimensions

    ASTRONOMY & GEOPHYSICS, Issue 2 2009
    Article first published online: 23 MAR 200
    A combination of NASA/ESA's Hubble Space Telescope and the European Southern Observatory's Very Large Telescope has revealed the 3-D movements of gas in distant galaxies, and sprung some surprises for observers. [source]

    Shaken but not stirred

    ASTRONOMY & GEOPHYSICS, Issue 2 2009
    Article first published online: 23 MAR 200
    Astronomers working with the Hubble Space Telescope have a new method of estimating the dark matter contribution to galaxies, from a group of objects unaffected by galaxy collisions all around. [source]

    Dwarf spheroidal galaxies in the M81 group of galaxies

    S. Lianou
    Abstract We study the properties of the dwarf galaxy population in the nearby interacting M81 group of galaxies. In particular, we are deriving the metallicity distribution functions, the ages and the star formation histories of these dwarf galaxies based on data from the Hubble Space Telescope's Advanced Camera for Surveys and the Sloan Digital Sky Survey. We are correlating this information with the dwarf galaxies' position in the group in order to derive the impact of interactions and environment on their evolution. Here we present preliminary results on the metallicity distribution functions of dwarf spheroidals in the M81 group ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Looking inside stars and looking for planets

    ASTRONOMY & GEOPHYSICS, Issue 6 2002
    Alan Penny
    Asteroseismology and extrasolar planets are the main science goals of the Eddington mission, now approved by ESA for a 2007 launch. Alan Penny presents a summary of the January 2002 RAS meeting that discussed the sciences of this wide-field high-precision photometric space telescope. Since the date of this meeting, ESA has decided to implement the mission in the framework of a 2007,08 launch. [source]

    The short history of infrared space telescopes

    D. Lemke
    Abstract While astronomical telescopes developed rather slowly over the last four centuries, infrared telescopes made a fast career in only four decades from high mountains to aircraft, balloons and satellites. They cover the huge wavelength region from 1 to 350 , m and have uncovered the cold and dust hidden universe. While until today all infrared space telescopes had diameters of <1 m, cooled infrared observatories with 3.5 to 6.5m mirrors will be sent into heliocentric orbits at L2 within the next few years ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]