The Sunyaev-Zeldovich Effect at 1 and 2 mm towards ROSAT Clusters

An observing campaign was devoted to the search for the Sunyaev-Zeldovich (S-Z) effect towards X-ray ROSAT Clusters in the millimetric spectral domain. A double channel (1.2 and 2 {\it mm}) photometer was installed at the focus of the 15m Swedish ESO Submillimeter Telescope (SEST) in Chile in september 1994 and 1995 and observations of the targets S1077, A2744, S295 and RXJ0658-5557 were gathered. Detections were found for A2744 at 1 {\it mm} and in both channels (at 1.2 and 2 {\it mm}) towards RXJ0658-5557. For the first time there is evidence for the S-Z enhancement and both the latter and the decrement were detected on the same source. We discuss astrophysical and systematic effects which could give origin to these signals.Comment: 6 pg Latex file (style file included) including 1 ps figure, XVIth Moriond Astrophysics Meeting "The Anisotropies of the Cosmic Microwave Background", Les Arcs, Savoie-France, March 16-23 199

ALMA SIS mixer optimization for stable operation

ABSTRACT The Atacama Large Millimeter/Submillimeter Array (ALMA), an interferometric radio telescope will have 66 array elements when complete. The ALMA Front End is designed to accommodate up to 10 receiver bands covering most of the wavelength range from 10 to 0.3 mm. Superconductor-insulator-superconductor (SIS) mixers are employed for Bands 3 (~3 mm) through 10 (~0.3 mm). Ordinarily the SIS bias is selected to achieve the lowest receiver noise temperatures. However, in order to obtain the lowest detection threshold, the SIS bias also needs to be optimized with respect to receiver stability. There are also other parameters to be optimized such as the magnetic field strength used to suppress the Josephson currents and avoidance of Shapiro. This paper will summarize the results of work carried out to derive the optimal operating parameters for the large number of mixers in use on the telescope so as to keep the telescope operating reliably and repeatably

Looking for the S-Z Effect towards Distant ROSAT Clusters of Galaxies

We report on observations of the Sunyaev-Zeldovich effect towards X-ray ROSAT clusters taken with a double channel (1.2 and 2 mm) photometer installed at the focus of the 15m SEST antenna in Chile. This paper describes the first results obtained for the high-z clusters S1077, A2744 and S295. Marginal detections were found for A2744 and at 1 mm for S1077. We discuss these data in terms of contamination of sources along the line of sight and give a constraint on the amplitude of the kinematic effect.Comment: 17 pg Latex file (using aasms4.sty) gzip'd tar'd uuencoded file including 1 ps figure, ApJ Letter in pres

HIFI spectroscopy of low-level water transitions in M82

We present observations of the rotational ortho-water ground transition, the two lowest para-water transitions, and the ground transition of ionised ortho-water in the archetypal starburst galaxy M82, performed with the HIFI instrument on the Herschel Space Observatory. These observations are the first detections of the para-H2O(111-000) (1113\,GHz) and ortho-H2O+(111-000) (1115\,GHz) lines in an extragalactic source. All three water lines show different spectral line profiles, underlining the need for high spectral resolution in interpreting line formation processes. Using the line shape of the para-H2O(111-000) and ortho-H2O+(111-000) absorption profile in conjunction with high spatial resolution CO observations, we show that the (ionised) water absorption arises from a ~2000 pc^2 region within the HIFI beam located about ~50 pc east of the dynamical centre of the galaxy. This region does not coincide with any of the known line emission peaks that have been identified in other molecular tracers, with the exception of HCO. Our data suggest that water and ionised water within this region have high (up to 75%) area-covering factors of the underlying continuum. This indicates that water is not associated with small, dense cores within the ISM of M82 but arises from a more widespread diffuse gas component.Comment: 5 pages, 4 figures. Accepted for publication in A&

The enhancement and decrement of the Sunyaev-Zel'dovich effect towards the ROSAT Cluster RXJ0658-5557The enhancement and decrement of the Sunyaev-Zeldovich effect towards the ROSAT Cluster RXJ0658-5557

Published in: Astrophys. J. 513 (1999) 23 citations recorded in [Science Citation Index] Abstract: We report simultaneous observations at 1.2 and 2 mm, with a double channel photometer on the SEST Telescope, of the X-ray cluster RXJ0658-5557 in search for the Sunyaev-Zel'dovich (S-Z). The S-Z data were analyzed using the relativistically correct expression for the Comptonization parameter and we find from the detected decrement (2.60 +/- 0.79) ~ 10^{-4}, which is consistent with that computed using the X-ray (ROSAT and ASCA) observations. The uncertainty includes contributions due to statistical uncertainty in the detection and systematics and calibration. The 1.2 {mm} channel data alone gives rise to a larger Comptonization parameter and this result is discussed in terms of contamination from foreground sources and/or dust in the cluster or from a possible systematic effect. We then make use of the combined analysis of the ROSAT and ASCA X-ray satellite observations to determine an isothermal model for the S-Z surface brightness. Since the cluster is asymmetrical and probably in a merging process, models are only approximate. The associated uncertainty can, however, be estimated by exploring a set of alternative models. We then find as the global uncertainty on the Comptonization parameter a factor of 1.3. Combining the S-Z and the X-ray measurements, we determine a value for the Hubble constant. The 2 mm data are consistent with H_0(q_0 = 1/2)= 53^{+38}_{-28} km/s Mpc^{-1}, where the uncertainty is dominated by the uncertainty in models of the X-ray plasma halo

AGN feedback and iron enrichment in the powerful radio galaxy, 4C+55.16

We present a detailed X-ray analysis of 4C+55.16, an unusual and interesting radio galaxy, located at the centre of a cool core cluster of galaxies. 4C+55.16 is X-ray bright (L(cluster)~10^45 erg/s), radio powerful, and shows clear signs of interaction with the surrounding intracluster medium. By combining deep Chandra (100 ks) with 1.4 GHz VLA observations, we find evidence of multiple outbursts from the central AGN, providing enough energy to offset cooling of the ICM (P_bubbles=6.7x10^44 erg/s). Furthermore, 4C+55.16 has an unusual intracluster iron distribution showing a plume-like feature rich in Fe L emission that runs along one of the X-ray cavities. The excess of iron associated with the plume is around 10^7M_sol. The metal abundances are consistent with being Solar-like, indicating that both SNIa and SNII contribute to the enrichment. The plume and southern cavity form a region of cool metal-rich gas, and at the edge of this region, there is a clear discontinuity in temperature (from kT~2.5 keV to kT~5.0 keV), metallicity (from ~0.4 solar to 0.8 solar), and surface brightness distribution, consistent with it being caused by a cold front. However, we also suggest that this discontinuity could be caused by cool metal-rich gas being uplifted from the central AGN along one of its X-ray cavities.Comment: 12 pages, 11 figures, 1 table, Accepted to MNRAS (minor revision

Phase locked 270-440 GHz local oscillator based on flux flow in long Josephson tunnel junctions

The combination of narrow linewidth and wide band tunability makes the Josephson flux flow oscillator (FFO) a perfect on-chip local oscillator for integrated sub-mm wave receivers for, e.g., spectral radio astronomy. The feasibility of phase locking the FFO to an external reference oscillator is demonstrated experimentally. A FFO linewidth as low as 1 Hz (determined by the resolution bandwidth of the spectrum analyzer) has been measured in the frequency range 270-440 GHz relative to a reference oscillator. This linewidth is far below the fundamental level given by shot and thermal noise of the free-running tunnel junction. The results of residual FFO phase noise measurements are also presented. Finally, we propose a single-chip fully superconductive receiver with two superconductor-insulator-superconductor mixers and an integrated phase-locked loop. (C) 2000 American Institute of Physics. [S0034-6748(00)01701-9]

HIFI spectroscopy of low-level water transitions in M82

We present observations of the rotational ortho-water ground transition, the two lowest para-water transitions, and the ground transition of ionised ortho-water in the archetypal starburst galaxy M82, performed with the HIFI instrument on the Herschel Space Observatory. These observations are the first detections of the para-H2O(111-000) (1113\,GHz) and ortho-H2O+(111-000) (1115\,GHz) lines in an extragalactic source. All three water lines show different spectral line profiles, underlining the need for high spectral resolution in interpreting line formation processes. Using the line shape of the para-H2O(111-000) and ortho-H2O+(111-000) absorption profile in conjunction with high spatial resolution CO observations, we show that the (ionised) water absorption arises from a ~2000 pc^2 region within the HIFI beam located about ~50 pc east of the dynamical centre of the galaxy. This region does not coincide with any of the known line emission peaks that have been identified in other molecular tracers, with the exception of HCO. Our data suggest that water and ionised water within this region have high (up to 75%) area-covering factors of the underlying continuum. This indicates that water is not associated with small, dense cores within the ISM of M82 but arises from a more widespread diffuse gas component.Comment: 5 pages, 4 figures. Accepted for publication in A&

Probing radio source environments via HI and OH absorption

We present the results of HI and OH absorption measurements towards a sample of radio sources using the Arecibo 305-m telescope and the GMRT. In total, 27 radio sources were searched for associated 21-cm HI absorption. One totally new HI absorption system was detected against the radio galaxy 3C258, while five previously known HI absorption systems, and one galaxy detected in emission, were studied with improved frequency resolution and/or sensitivity. Our sample included 17 GPS and CSS objects, 4 of which exhibit HI absorption. This detection rate of ~25% compares with a value of ~40% by Vermeulen et al. for similar sources. We detected neither OH emission nor absorption towards any of the sources that were observed at Arecibo, and estimate a limit on the abundance ratio of N(HI)/N(OH)>4x10^6 for 3C258. We have combined our results with those from other available HI searches to compile a heterogeneous sample of 96 radio sources consisting of 27 GPS, 35 CSS, 13 flat spectrum and 21 large sources. The HI absorption detection rate is highest (~45%) for the GPS sources and least for the large sources. We find HI column density to be anticorrelated with source size, as reported earlier by Pihlstr\"om et al. The HI column density shows no significant dependence on either redshift or luminosity, which are themselves strongly correlated. These results suggest that the environments of radio sources on GPS/CSS scales are similar at different redshifts. Further, in accordance with the unification scheme, the GPS/CSS galaxies have an HI detection rate of ~40% which is significantly higher than the detection rate (~20%) towards the GPS/CSS quasars. Also, the principal (strongest) absorption component detected towards GPS sources appears blue-shifted in ~65% of the cases, in agreement with the growing evidence for jet-cloud interactions.Comment: Abridged abstract, 22 pages, 21 figures, moderately revised, accepted for publication in MNRA