897 research outputs found
Exploring the gravitationally lensed system HE 1104-1805: Near-IR Spectroscopy
(Abridged) A new technique for the spatial deconvolution of spectra is
applied to near-IR (0.95 - 2.50 micron) NTT/SOFI spectra of the lensed,
radio-quiet quasar HE 1104-1805. The continuum of the lensing galaxy is
revealed between 1.5 and 2.5 micron. It is used in combination with previous
optical and IR photometry to infer a plausible redshift in the range 0.8 < z <
1.2. Modeling of the system shows that the lens is probably composed of the red
galaxy seen between the quasar images and a more extended component associated
with a galaxy cluster with fairly low velocity dispersion (~ 575 km/s). The
spectra of the two lensed images of the source show no trace of reddening at
the redshift of the lens nor at the redshift of the source. Additionally, the
difference between the spectrum of the brightest component a nd that of a
scaled version of the faintest component is a featureless continuum. Broad and
narrow emission lines, including the FeII features, are perfectly subtracted.
The very good quality of our spectrum makes it possible to fit precisely the
optical Fe II feature, taking into account the underlying continuum over a wide
wavelength range. HE 1104-1805 can be classified as a weak Fe II emitter.
Finally, the slope of the continuum in the brightest image is steeper than the
continuum in the faintest image and supports the finding by Wisotzki et al.
(1993) that the brightest image is microlensed. This is particularly
interesting in view of the new source reconstruction methods from
multiwavelength photometric monitoring.Comment: to be published in A&A, 8 pages, 9 postscript figure
Confirmation of two extended objects along the line of sight to PKS1830-211 with ESO-VLT adaptive optics imaging
We report on new high-resolution near-infrared images of the gravitationally
lensed radio source PKS1830-211, a quasar at z=2.507. These adaptive optics
observations, taken with the Very Large Telescope (VLT), are further improved
through image deconvolution. They confirm the presence of a second object along
the line of sight to the quasar, in addition to the previously known spiral
galaxy. This additional object is clearly extended in our images. However, its
faint luminosity does not allow to infer any photometric redshift. If this
galaxy is located in the foreground of PKS1830-211, it complicates the modeling
of this system and decreases the interest in using PKS1830-211 as a means to
determine H0 via the time delay between the two lensed images of the quasar.Comment: Accepted in A&A Letter
IR Colors and Sizes of Faint Galaxies
We present J and Ks band galaxy counts down to J=24 and Ks=22.5 obtained with
the new infrared imager/spectrometer, SOFI, at the ESO New Technology
Telescope. The co-addition of short, dithered, images led to a total exposure
time of 256 and 624 minutes respectively, over an area of arcmin
centered on the NTT Deep Field. The total number of sources with S/N is
1569 in the J sample and 1025 in the Ks-selected sample. These are the largest
samples currently available at these depths. A d/d relation with slope
of in J and in Ks is found with no evident sign of a
decline at the magnitude limit. The observed surface density of ``small''
sources is much lower than ``large'' ones at bright magnitudes and rises more
steeply than the large sources to fainter magnitudes. Fainter than
and Ks, small sources dominate the number counts. Galaxies get redder
in J-K down to
J and Ks. At fainter magnitudes, the median color becomes
bluer with an accompanying increase in the compactness of the galaxies. We show
that the blue, small sources which dominate the faint IR counts are not
compatible with a high redshift () population. On the contrary, the
observed color and compactness trends, together with the absence of a turnover
at faint magnitudes and the dominance of small sources, can be naturally
explained by an increasing contribution of sub- galaxies when going to
fainter apparent magnitudes. Such evidence strongly supports the existence of a
steeply rising () faint end of the local infrared luminosity
function of galaxies - at least for luminosities .Comment: Accepted for publication on A&A; 15 pages, 13 figure
Investigation of bonding between metals and ceramics I : nickel, cobalt, iron, or chromium with boron carbide
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