12 research outputs found
A VSA search for the extended Sunyaev-Zel'dovich Effect in the Corona Borealis Supercluster
We present interferometric imaging at 33 GHz of the Corona Borealis
supercluster, using the extended configuration of the Very Small Array. A total
area of 24 deg^2 has been imaged, with an angular resolution of 11 arcmin and a
sensitivity of 12 mJy/beam. The aim of these observations is to search for
Sunyaev-Zel'dovich (SZ) detections from known clusters of galaxies in this
supercluster and for a possible extended SZ decrement due to diffuse warm/hot
gas in the intercluster medium. We measure negative flux values in the
positions of the ten richest clusters in the region. Collectively, this implies
a 3.0-sigma detection of the SZ effect. In the clusters A2061 and A2065 we find
decrements of approximately 2-sigma. Our main result is the detection of two
strong and resolved negative features at -70+-12 mJy/beam (-157+-27 microK) and
-103+-10 mJy/beam (-230+-23 microK), respectively, located in a region with no
known clusters, near the centre of the supercluster. We discuss their possible
origins in terms of primordial CMB anisotropies and/or SZ signals related to
either unknown clusters or to a diffuse extended warm/hot gas distribution. Our
analyses have revealed that a primordial CMB fluctuation is a plausible
explanation for the weaker feature (probability of 37.82%). For the stronger
one, neither primordial CMB (probability of 0.33%) nor SZ can account alone for
its size and total intensity. The most reasonable explanation, then, is a
combination of both primordial CMB and SZ signal. Finally, we explore what
characteristics would be required for a filamentary structure consisting of
warm/hot diffuse gas in order to produce a significant contribution to such a
spot taking into account the constraints set by X-ray data.Comment: 16 pages, 10 figures. Accepted in MNRA
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
A High-resolution SZ View of the Warm-Hot Universe
We outline advances in the understanding of thermodynamic/kinematic properties of the warm-hot universe that can come through resolved measurements of the Sunyaev Zeldovich effects. Many advances will be enabled by new (sub)millimeter instrumentation on existing facilities, but truly transformative advances will require new mm/submm facilities
Future Science Prospects for AMI
The Arcminute Microkelvin Imager (AMI) is a telescope specifically designed
for high sensitivity measurements of low-surface-brightness features at
cm-wavelength and has unique, important capabilities. It consists of two
interferometer arrays operating over 13.5-18 GHz that image structures on
scales of 0.5-10 arcmin with very low systematics. The Small Array (AMI-SA; ten
3.7-m antennas) couples very well to Sunyaev-Zel'dovich features from galaxy
clusters and to many Galactic features. The Large Array (AMI-LA; eight 13-m
antennas) has a collecting area ten times that of the AMI-SA and longer
baselines, crucially allowing the removal of the effects of confusing radio
point sources from regions of low surface-brightness, extended emission.
Moreover AMI provides fast, deep object surveying and allows monitoring of
large numbers of objects. In this White Paper we review the new science - both
Galactic and extragalactic - already achieved with AMI and outline the
prospects for much more.Comment: 20 pages, 11 figures; white paper. Revised author list, section IB,
section IIIC2, reference