53 research outputs found
zCOSMOS: A Large VLT/VIMOS redshift survey covering 0 < z < 3 in the COSMOS field
zCOSMOS is a large redshift survey that is being undertaken in the COSMOS field using 600 hours of observation with the VIMOS spectrograph on the 8-m VLT. The survey is designed to characterise the environments of COSMOS galaxies from the 100 kpc scales of galaxy groups up to the 100 Mpc scale of the cosmic web and to produce diagnostic information on galaxies and active galactic nuclei. The zCOSMOS survey consists of two parts: (a) zCOSMOS-bright, a magnitude-limited I-band IAB < 22.5 sample of about 20,000 galaxies with 0.1 < z < 1.2 covering the whole 1.7 deg2 COSMOS ACS field and designed to mimic the parameters of the 2dfGRS; and (b) zCOSMOS-deep, a survey of approximately 10,000 galaxies selected through colour-selection criteria to have 1.4 < z < 3.0, within the central 1 deg2. This paper describes the survey design and the construction of the target catalogues, and briefly outlines the observational program and the data pipeline. In the first observing season, spectra of 1303 zCOSMOS-bright targets and of 977 zCOSMOS-deep targets have been obtained. These are briefly analysed to demonstrate the characteristics that may be expected from zCOSMOS, and particularly zCOSMOS-bright, when it is finally completed between 2008-2009. The power of combining spectroscopic and photometric redshifts is demonstrated, especially in correctly identifying the emission line in single-line spectra and in determining which of the less reliable spectroscopic redshifts are correct and which are incorrect. Our zCOSMOS-deep spectra demonstrate the effectiveness of our selection techniques to isolate high redshift galaxies at 1.4 < z < 3.0 and of VIMOS to measure their redshifts using ultraviolet absorption lines
Enhanced star formation rates in AGN hosts with respect to inactive galaxies from PEP-Herschel observations
We compare the average star formation (SF) activity in X-ray selected AGN
hosts with mass-matched control inactive galaxies,including star forming and
quiescent sources, at 0.5<z<2.5. Recent observations carried out by PACS, the
60-210um Herschel photometric camera, in GOODS-S, GOODS-N and COSMOS allow us
to unbiasedly estimate the far-IR luminosity, and hence the SF properties, of
the two samples. Accurate AGN host stellar masses are measured by decomposing
their total emission into the stellar and nuclear components. We find a higher
average SF activity in AGN hosts with respect to non-AGNs. The level of SF
enhancement is modest (~0.26dex at ~3sigma) at low X-ray luminosities
(Lx10sigma) for bright AGNs.
However, when comparing to star forming galaxies only, AGN hosts are broadly
consistent with the locus of their `main sequence'. We investigate the relative
far-IR luminosity distributions of active and inactive galaxies, and find a
higher fraction of PACS detected, hence normal and highly star forming systems
among AGN hosts. Although different interpretations are possible, we explain
our findings as a consequence of a twofold AGN growth path: faint AGNs evolve
through secular processes, with instantaneous AGN accretion not tightly linked
to the current total SF in the host, while luminous AGNs co-evolve with their
hosts through periods of enhanced AGN activity and SF, possibly through major
mergers. While an increased SF with respect to non-AGNs of similar mass is
expected in the latter, we interpret the modest SF offsets measured in low-Lx
AGN hosts as either a) generated by non-synchronous accretion and SF histories
in a merger scenario or b) due to possible connections between instantaneous SF
and accretion that can be induced by smaller scale (non-major merger)
mechanisms. Far-IR luminosity distributions favour the latter scenario.Comment: Final versio
Polarized blazar X-rays imply particle acceleration in shocks
Most of the light from blazars, active galactic nuclei with jets of magnetized plasma that point nearly along the line of sight, is produced by high-energy particles, up to around 1 TeV. Although the jets are known to be ultimately powered by a supermassive black hole, how the particles are accelerated to such high energies has been an unanswered question. The process must be related to the magnetic field, which can be probed by observations of the polarization of light from the jets. Measurements of the radio to optical polarization—the only range available until now—probe extended regions of the jet containing particles that left the acceleration site days to years earlier1,2,3, and hence do not directly explore the acceleration mechanism, as could X-ray measurements. Here we report the detection of X-ray polarization from the blazar Markarian 501 (Mrk 501). We measure an X-ray linear polarization degree ΠX of around 10%, which is a factor of around 2 higher than the value at optical wavelengths, with a polarization angle parallel to the radio jet. This points to a shock front as the source of particle acceleration and also implies that the plasma becomes increasingly turbulent with distance from the shock
Tracking the X-ray Polarization of the Black Hole Transient Swift J1727.8-1613 during a State Transition
We report on a campaign on the bright black hole X-ray binary Swift
J1727.81613 centered around five observations by the Imaging X-ray
Polarimetry Explorer (IXPE). This is the first time it has been possible to
trace the evolution of the X-ray polarization of a black hole X-ray binary
across a hard to soft state transition. The 2--8 keV polarization degree slowly
decreased from 4\% to 3\% across the five observations, but
remained in the North-South direction throughout. Using the Australia Telescope
Compact Array (ATCA), we measure the intrinsic 7.25 GHz radio polarization to
align in the same direction. Assuming the radio polarization aligns with the
jet direction (which can be tested in the future with resolved jet images),
this implies that the X-ray corona is extended in the disk plane, rather than
along the jet axis, for the entire hard intermediate state. This in turn
implies that the long (10 ms) soft lags that we measure with the
Neutron star Interior Composition ExploreR (NICER) are dominated by processes
other than pure light-crossing delays. Moreover, we find that the evolution of
the soft lag amplitude with spectral state differs from the common trend seen
for other sources, implying that Swift J1727.81613 is a member of a hitherto
under-sampled sub-population.Comment: Submitted to ApJ. 20 pages, 8 figure
X-ray Polarization Observations of BL Lacertae
Blazars are a class of jet-dominated active galactic nuclei with a typical
double-humped spectral energy distribution. It is of common consensus the
Synchrotron emission to be responsible for the low frequency peak, while the
origin of the high frequency hump is still debated. The analysis of X-rays and
their polarization can provide a valuable tool to understand the physical
mechanisms responsible for the origin of high-energy emission of blazars. We
report the first observations of BL Lacertae performed with the Imaging X-ray
Polarimetry Explorer ({IXPE}), from which an upper limit to the polarization
degree 12.6\% was found in the 2-8 keV band. We contemporaneously
measured the polarization in radio, infrared, and optical wavelengths. Our
multiwavelength polarization analysis disfavors a significant contribution of
proton synchrotron radiation to the X-ray emission at these epochs. Instead, it
supports a leptonic origin for the X-ray emission in BL Lac.Comment: 17 pages, 5 figures, accepted for publication in ApJ
Psychometric Properties and Correlates of Precarious Manhood Beliefs in 62 Nations
Precarious manhood beliefs portray manhood, relative to womanhood, as a social status that is hard to earn, easy to lose, and proven via public action. Here, we present cross-cultural data on a brief measure of precarious manhood beliefs (the Precarious Manhood Beliefs scale [PMB]) that covaries meaningfully with other cross-culturally validated gender ideologies and with country-level indices of gender equality and human development. Using data from university samples in 62 countries across 13 world regions (N = 33,417), we demonstrate: (1) the psychometric isomorphism of the PMB (i.e., its comparability in meaning and statistical properties across the individual and country levels); (2) the PMB’s distinctness from, and associations with, ambivalent sexism and ambivalence toward men; and (3) associations of the PMB with nation-level gender equality and human development. Findings are discussed in terms of their statistical and theoretical implications for understanding widely-held beliefs about the precariousness of the male gender role
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