332 research outputs found
The discovery of a type II quasar at z= 1.65 with integral-field spectroscopy
In this Letter we report the serendipitous discovery of a genuine type II quasar at z= 1.65 using integral-field data from the Visual Multi-Object Spectrograph (VIMOS) on the Very Large Telescope (VLT). This is the first discovery of a type II quasar at z > 1 from optical data alone. J094531-242831, hereafter J0945-2428, exhibits strong narrow (v < 1500 km s-1) emission lines, has a resolved host galaxy, and is undetected to a radio flux density limit of S5 GHz= 0.15 mJy (3σ) . All of these characteristics lead us to believe that J0945-2428 is a bona fide type II quasar. The luminosity of the narrow emission lines in this object suggest that the intrinsic power of the central engine is similar to that found in powerful radio galaxies, indicative of a similarly large supermassive black hole of ∼ 3 × 108 M⊙ (assuming that it is accreting at its Eddington limit). However, from near-infrared imaging observations we find that the old stellar population in the host galaxy has a luminosity of ∼ 0.2 L⋆, mildly inconsistent with the correlation between black hole mass and bulge luminosity found locally, although the uncertainty in the black hole mass estimate is large.
This discovery highlights the power that integral-field units have in discovering hidden populations of objects, particularly the sought-after type II quasars, which are invoked to explain the hard X-ray background. As such, future large integral-field surveys could open up a new window on the obscured accretion activity in the Universe
Integral-field studies of the high-redshift Universe
We present results from a new method of exploring the distant Universe. We
use 3-D spectroscopy to sample a large cosmological volume at a time when the
Universe was less than 3 billion years old to investigate the evolution of
star-formation activity. Within this study we also discovered a high redshift
type-II quasar which would not have been identified with imaging studies alone.
This highlights the crucial role that integral-field spectroscopy may play in
surveying the distant Universe in the future.Comment: From proceedings of Euro3D Spectroscopy annual RTN network meeting
(ed. J. Walsh). 5 pages, accepted for publication in Astron. Nach
Evidence of a link between the evolution of clusters and their AGN fraction
‘The definitive version is available at www3.interscience.wiley.com .' Copyright Blackwell Publishing / Royal Astronomical Society. DOI: 10.1111/j.1365-2966.2009.14513.xPeer reviewe
Distant galaxy clusters in the COSMOS field found by HIROCS
We present the first high-redshift galaxy cluster candidate sample from the
HIROCS survey found in the COSMOS field. It results from a combination of
public COSMOS with proprietary H-band data on a 0.66 square degree part of the
COSMOS field and comprises 12 candidates in the redshift range 1.23 < z < 1.55.
We find an increasing fraction of blue cluster members with increasing
redshift. Many of the blue and even some of the reddest member galaxies exhibit
disturbed morphologies as well as signs of interaction.Comment: 5 pages, 5 figures, in print format, accepted for publication by A&A
Letter
Paclitaxel for malignant pleural mesothelioma: a phase II study of the EORTC Lung Cancer Cooperative Group.
The EORTC Lung Cancer Cooperative Group undertook a phase II study of paclitaxel in 25 chemotherapy-naive patients with malignant pleural mesothelioma. Paclitaxel was given intravenously at a dose of 200 mg m-2 as a 3 h infusion every 3 weeks, after standard premedication with corticosteroids and antihistamines. This regimen was well tolerated, with < 4% of cycles resulting in severe toxicity. No major objective responses were observed and ten patients had stable disease. Median survival time was 39 weeks and the 1 year survival rate was 30%. In conclusion, paclitaxel at the dose and schedule investigated in this trial had no major activity in the treatment of malignant pleural mesothelioma
3D-Matched-Filter Galaxy Cluster Finder I: Selection Functions and CFHTLS Deep Clusters
We present an optimised galaxy cluster finder, 3D-Matched-Filter (3D-MF),
which utilises galaxy cluster radial profiles, luminosity functions and
redshift information to detect galaxy clusters in optical surveys. This method
is an improvement over other matched-filter methods, most notably through
implementing redshift slicing of the data to significantly reduce line-of-sight
projections and related false positives. We apply our method to the
Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) Deep fields, finding ~170
galaxy clusters per square degree in the 0.2 <= z <= 1.0 redshift range. Future
surveys such as LSST and JDEM can exploit 3D-MF's automated methodology to
produce complete and reliable galaxy cluster catalogues. We determine the
reliability and accuracy of the statistical approach of our method through a
thorough analysis of mock data from the Millennium Simulation. We detect
clusters with 100% completeness for M_200 >= 3.0x10^(14)M_sun, 88% completeness
for M_200 >= 1.0x10^(14)M_sun, and 72% completeness well into the 10^(13)M_sun
cluster mass range. We show a 36% multiple detection rate for cluster masses >=
1.5x10^(13)M_sun and a 16% false detection rate for galaxy clusters >~
5x10^(13)M_sun, reporting that for clusters with masses <~ 5x10^(13)M_sun false
detections may increase up to ~24%. Utilising these selection functions we
conclude that our galaxy cluster catalogue is the most complete CFHTLS Deep
cluster catalogue to date.Comment: 18 pages, 17 figures, 5 tables; v2: added Fig 5, minor edits to match
version published in MNRA
Multi-object spectroscopy of low-redshift EIS clusters IV. Reliability of matched-filter results at z~0.3-0.4
abridged) In this paper we present new redshifts for 747 galaxies in 23 ESO
Imaging Survey (EIS) cluster fields. We use the "gap"-technique to search for
significant overdensities in redshift space for identifying groups/clusters of
galaxies. In this way we spectroscopically confirm systems in 10 of the 23
cluster candidate fields with a matched-filter estimated redshift z_MF=0.3-0.4
and with spectroscopic redshifts in the range from z=0.158 to z=0.534. We find
that the systems identified in the present paper span a broad range of
one-dimensional velocity dispersion (175-497 km/s) and richness
(12L*<=L<=65L*). Both undersampling and contamination by substructures
contribute to the uncertainty of these measurements. From the analysis of the
colours of the galaxy populations we find that ~60% of the spectroscopically
confirmed systems have a "significant" red sequence with a colour matching
passive stellar evolution models. With this paper we complete our spectroscopic
survey of the fields of 58 EIS cluster candidates with estimated redshifts
z<=0.4. We have measured a total of 1954 galaxy redshifts in the range z=0.0065
to z=0.6706. Of the 58 systems we confirm 42 (~75%) with redshifts between
z=0.095 and z=0.534.Comment: Accepted for publication in A&A, 19 pages, 11 figure
Lyman-alpha emission galaxies at a redshift of z = 5.7 in the FORS Deep Field
We present the results of a search for Lyman-alpha emission galaxies at z~
5.7 in the FORS Deep Field. The objective of this study is to improve the faint
end of the luminosity function of high-redshift Lyman-alpha emitting galaxies
and to derive properties of intrinsically faint Lyman-alpha emission galaxies
in the young universe. Using FORS2 at the ESO VLT and a set of special
interference filters, we identified candidates for high-redshift Lyman-alpha
galaxies. We then used FORS2 in spectroscopic mode to verify the
identifications and to study their spectral properties. The narrow-band
photometry resulted in the detection of 15 likely Lyman-alpha emission
galaxies. Spectra with an adequate exposure time could be obtained for eight
galaxies. In all these cases the presence of Lyman-alpha emission at z = 5.7
was confirmed spectroscopically. The line fluxes of the 15 candidates range
between 3 and 16 * 10^-21 Wm^-2, which corresponds to star-formation rates not
corrected for dust between 1 and 5 Msun/yr. The luminosity function derived for
our photometrically identified objects extends the published luminosity
functions of intrinsically brighter Lyman-alpha galaxies. With this technique
the study of high-redshift Lyman-alpha emission galaxies can be extended to low
intrinsic luminosities.Comment: 9 pages, 17 figures. Accepted by A&A. PDF version with higher
resolution figures here:
http://www.lsw.uni-heidelberg.de/users/jheidt/fdf/pubs/fdflae5_7_110406.pd
Excess AGN Activity in the z=2.30 Protocluster in HS 1700+64
We present the results of spectroscopic, narrow-band and X-ray observations
of a z=2.30 protocluster in the field of the QSO HS 1700+643. Using a sample of
BX/MD galaxies, which are selected to be at z~2.2-2.7 by their rest-frame
ultraviolet colours, we find that there are 5 protocluster AGN which have been
identified by characteristic emission-lines in their optical/near-IR spectra;
this represents an enhancement over the field significant at ~98.5 per cent
confidence. Using a ~200 ks Chandra/ACIS-I observation of this field we detect
a total of 161 X-ray point sources to a Poissonian false-probability limit of
4x10^{-6} and identify 8 of these with BX/MD galaxies. Two of these are
spectroscopically confirmed protocluster members and are also classified as
emission-line AGN. When compared to a similarly selected field sample the
analysis indicates this is also evidence for an enhancement of X-ray selected
BX/MD AGN over the field, significant at ~99 per cent confidence. Deep Lya
narrow-band imaging reveals that a total of 4/123 Lya emitters (LAEs) are found
to be associated with X-ray sources, with two of these confirmed protocluster
members and one highly likely member. We do not find a significant enhancement
of AGN activity in this LAE sample over that of the field (result significant
at only 87 per cent confidence). The X-ray emitting AGN fractions for the BX/MD
and LAE samples are found to be 6.9_{-4.4}^{+9.2} and 2.9_{-1.6}^{+2.9} per
cent, respectively, for protocluster AGN with L_{2-10 keV}>4.6x10^{43} erg
s^{-1} at z=2.30. These findings are similar to results from the z=3.09
protocluster in the SSA 22 field found by Lehmer et al. (2009), in that both
suggest AGN activity is favoured in dense environments at z>2.Comment: 8 pages, 2 figures. Accepted for publication in MNRAS
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