Suzaku measurement of Abell 2204's intracluster gas temperature profile out to 1800 kpc

Context: Measurements of intracluster gas temperatures out to large radii are important for the use of clusters for precision cosmology and for studies of cluster physics. Previous attempts to measure robust temperatures at cluster virial radii failed. Aims: The goal of this work is to measure the temperature profile of the very relaxed galaxy cluster Abell 2204 out to large radii, possibly reaching the virial radius. Methods: Taking advantage of its low particle background due to its low-Earth orbit, Suzaku data are used to measure the outer temperature profile of Abell 2204. These data are combined with Chandra and XMM-Newton data of the same cluster in order to make the connection to the inner regions, unresolved by Suzaku, and to determine the smearing due to Suzaku's PSF. Results: The temperature profile of Abell 2204 is determined from 10 kpc to 1800 kpc, close to an estimate of r200 (the approximation to the virial radius). The temperature rises steeply from below 4 keV in the very center up to more than 8 keV in the intermediate range and then decreases again to about 4 keV at the largest radii. Varying the measured particle background normalization artificially by +-10 percent does not change the results significantly. Predictions for outer temperature profiles based on hydrodynamic simulations show good agreement. In particular, we find the observed temperature profile to be slightly steeper but consistent with a drop of a factor of 0.6 from 0.3 r200 to r200, as predicted by simulations. Conclusions: Temperature measurements up to the virial radius seem feasible with Suzaku, when a careful analysis of the different background components and the effects of the PSF is performed. The result obtained here indicates that numerical simulations capture the intracluster gas physics well in cluster outskirts.Comment: 7 pages; Astronomy and Astrophysics, accepted; additional systematic effects have been quantified, results unchanged; also available at http://www.reiprich.ne

An XMM-Newton Observation of the Massive Edge-on Sb Galaxy NGC 2613

We present an XMM-Newton observation of the massive edge-on Sb galaxy NGC 2613. We discover that this galaxy contains a deeply embedded active nucleus with a 0.3-10 keV luminosity of 3.3x10^40 erg/s and a line-of-sight absorption column of 1.2x10^23 cm^-2. Within the 25 mag/arcsec^2 optical B-band isophote of the galaxy, we detect an additional 4 sources with an accumulated luminosity of 4.3x10^39 erg/s. The bulk of the unresolved X-ray emission spatially follows the near-infrared (NIR) K-band surface brightness distribution; the luminosity ratio L_X/L_K ~ 8x10^-4 is consistent with that inferred from galactic discrete sources. This X-ray-NIR association and the compatibility of the X-ray spectral fit with the expected spectrum of a population of discrete sources suggest that low-mass X-ray binaries (LMXBs) are the most likely emitters of the unresolved emission in the disk region. The remaining unresolved emission is primarily due to extraplanar hot gas. The luminosity of this gas is at least a factor of 10 less than that predicted by recent simulations of intergalactic gas accretion by such a massive galaxy with a circular rotation speed V_c ~ 304 km/s^2 (Toft et al. 2002). Instead, we find that the extraplanar hot gas most likely represents discrete extensions away from the disk, including two ``bubble-like'' features on either side of the nucleus. These extensions appear to correlate with radio continuum emission and, energetically, can be easily explained by outflows from the galactic disk.Comment: 17 pages, accepted by MNRA

PAHs in the Halo of NGC 5529

We present sensitive ISO $\lambda 6.7 \mu$m observations of the edge-on galaxy, NGC 5529, finding an extensive MIR halo around NGC 5529. The emission is dominated by PAHs in this band. The PAH halo has an exponential scale height of 3.7 kpc but can still be detected as far as $\approx 10$ kpc from the plane to the limits of the high dynamic range (1770/1) data. This is the most extensive PAH halo yet detected in a normal galaxy. This halo shows substructure and the PAHs likely originate from some type of disk outflow. PAHs are long-lived in a halo environment and therefore continuous replenishment from the disk is not required (unless halo PAHs are also being destroyed or removed), consistent with the current low SFR of the galaxy. The PAHs correlate spatially with halo H$\alpha$ emission, previously observed by Miller & Veilleux (2003); both components are likely excited/ionized by in-disk photons that are leaking into the halo. The presence of halo gas may be related to the environment of NGC 5529 which contains at least 17 galaxies in a small group of which NGC 5529 is the dominant member. Of these, we have identified two new companions from the SDSS.Comment: 16 pages, 5 gif figures, accepted for publication in A&A, For pdf with higher quality figures, see http://www.astro.queensu.ca/~irwi

Proper motion L and T dwarf candidate members of the Pleiades

We present the results of a deep optical-near-infrared multi-epoch survey covering 2.5 square degrees of the Pleiades open star cluster to search for new very-low-mass brown dwarf members. A significant (~ 5 year) epoch difference exists between the optical (CFH12k I-, Z-band) and near infrared (UKIRT WFCAM J-band) observations. We construct I,I-Z and Z,Z-J colour magnitude diagrams to select candidate cluster members. Proper motions are computed for all candidate members and compared to the background field objects to further refine the sample. We recover all known cluster members within the area of our survey. In addition, we have discovered 9 new candidate brown dwarf cluster members. The 7 faintest candidates have red Z-J colours and show blue near-infrared colours. These are consistent with being L and T-type Pleiads. Theoretical models predict their masses to be around 11 Jupiter masses. There is 1 errata for this paperComment: 12 pages, 9 figures, 4 tables, accepted for publication in MNRAS Errata: 1 tabl

Understanding local Dwarf Spheroidals and their scaling relations under MOdified Newtonian Dynamics

We use a specific form of the interpolation function in the MOND formalism, which optimally accounts for the internal structure of dwarf spheroidal (dSph) galaxies, to explore the consequences it has on the scaling relations seen in these systems.}} {{The particular form of the interpolation function we used leads to a law of gravity that does not degrade the good fit of the MOND proposal on galactic scales, and in fact, slightly improves the accordance with observations at dSph scales. This formalism yields a good description of gravitational phenomena without the need of invoking any still undetected and hypothetically dominant dark matter, in the weak field regime probed by local dSph galaxies.}} {{Isothermal equilibrium density profiles then yield projected surface density profiles for the local dSph galaxies in very good agreement with observational determinations, for values of the relevant parameters as inferred from recent observations of these Galactic satellites. The observed scaling relations for these systems are also naturally accounted for within the proposed scheme, including a previously unrecognised correlation of the inferred mass-to-light ratios of local dSph's with the ages of their stellar populations, which is natural in modified gravity schemes in the absence of dark matter.}} {The results shed some light on the form that the MOND interpolating function may have in the most challenging regime, which occurs at moderate accelerations and intermediate mass--weighted lengths.Comment: 8 pages, 4 figures, 1 table, Accepted for publication in Astronomy and Astrophysics. Copy matches published versio

ISO continuum observations of quasars at z=1-4 I.Spectral energy distributions of quasars from the UV to far-infrared

Eight luminous quasars with $-30 < M_B < -27$ at z = 1.4 - 3.7 have been observed in the mid- and far-infrared using ISO. All the quasars have been detected in the mid-infrared bands of ISOCAM, while no far-infrared detections have been made with ISOPHOT. Supplementing ISO observations with photometry in the optical and near-infrared made from the ground mostly within 17 months after the ISO observations, SEDs (Spectral Energy Distributions) from the UV to far-infrared have been obtained. SEDs (Spectral Energy Distributions) from the UV to far-infrared have been obtained while supplementing ISO observations with photometry in the optical and near-infrared made from the ground within 17 months. The SEDs are compared with the MED (Mean spectral Energy Distributions) of low-redshift quasars with $-27 < M_B < -22$. It is shown that our far-infrared observations were limited by confusion noise due to crowded sources.Comment: 9 pages, 3 figures: accepted for publication in Astronomy and Astrophysic

XMM-Newton Spectroscopy of the Cluster of Galaxies 2A 0335+096

We present here the results of a deep (130 ks) XMM-Newton observation of the cluster of galaxies 2A 0335+096. The deep exposure allows us to study in detail its temperature structure and its elemental abundances. We fit three different thermal models and find that the multi-temperature wdem model fits our data best. We find that the abundance structure of the cluster is consistent with a scenario where the relative number of Type Ia supernovae contributing to the enrichment of the intra-cluster medium is ~25%, while the relative number of core collapse supernovae is ~75%. Comparison of the observed abundances to the supernova yields does not allow us to put any constrains on the contribution of Pop III stars to the enrichment of the ICM. Radial abundance profiles show a strong central peak of both Type Ia and core collapse supernova products. Both the temperature and iron abundance maps show an asymmetry in the direction of the elongated morphology of the surface brightness. In particular the temperature map shows a sharp change over a brightness edge on the southern side of the core, which was identified as a cold front in the Chandra data. This suggests that the cluster is in the process of a merger with a subcluster. Moreover, we find that the blobs or filaments discovered in the core of the cluster by Chandra are, contrary to the previous results, colder than the ambient gas and they appear to be in pressure equilibrium with their environment.Comment: Accepted for publication in A&A, 19 page

Gravitational Lensing at Millimeter Wavelengths

With today's millimeter and submillimeter instruments observers use gravitational lensing mostly as a tool to boost the sensitivity when observing distant objects. This is evident through the dominance of gravitationally lensed objects among those detected in CO rotational lines at z>1. It is also evident in the use of lensing magnification by galaxy clusters in order to reach faint submm/mm continuum sources. There are, however, a few cases where millimeter lines have been directly involved in understanding lensing configurations. Future mm/submm instruments, such as the ALMA interferometer, will have both the sensitivity and the angular resolution to allow detailed observations of gravitational lenses. The almost constant sensitivity to dust emission over the redshift range z=1-10 means that the likelihood for strong lensing of dust continuum sources is much higher than for optically selected sources. A large number of new strong lenses are therefore likely to be discovered with ALMA, allowing a direct assessment of cosmological parameters through lens statistics. Combined with an angular resolution <0.1", ALMA will also be efficient for probing the gravitational potential of galaxy clusters, where we will be able to study both the sources and the lenses themselves, free of obscuration and extinction corrections, derive rotation curves for the lenses, their orientation and, thus, greatly constrain lens models.Comment: 69 pages, Review on quasar lensing. Part of a LNP Topical Volume on "Dark matter and gravitational lensing", eds. F. Courbin, D. Minniti. To be published by Springer-Verlag 2002. Paper with full resolution figures can be found at ftp://oden.oso.chalmers.se/pub/tommy/mmviews.ps.g

Booms and busts in commodity markets: bubbles or fundamentals?

This paper considers whether there were periodically collapsing rational speculative bubbles in commodity prices over a 40-year period from the late 1960s. We apply a switching regression approach to a broad range of commodities using two different measures of fundamental values—estimated from convenience yields and from a set of macroeconomic factors believed to affect commodity demand. We find reliable evidence for bubbles only among crude oil and feeder cattle, showing the popular belief that the extreme price movements observed in commodity markets were caused by pure speculation to be unsustainabl

Research to action to address inequities: the experience of the Cape Town Equity Gauge

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