Ketenimine (CH2CNH) has been detected in absorption toward the starforming region Sagittarius B2(N) with the 100-m Green Bank Telescope (GBT) by means of three rotational transitions: 7(sub 16)-8(sub 08) at 41.5 GHz, 8(sub 19)-9(sub 09), at 23.2 GHz, and 9(sub 18)-10(sub 0,10) at 4.9 GHz. Ketenimine has a sparse rotational spectrum below 50 GHz. From transition line strength arguments, the spectral lines found are the ones most likely to be detected and occur in spectral regions that have little possibility of confusion with other molecular species. Partially resolved hyperfine structure is apparent in the 4.9 GHz transition which has energy levels approximately 50 K above ground state level; the absorption seen in this transition appears to be emanating from gas in close proximity to the LMH hot core that has a systemic LSR velocity of +64 kilometers per second. By comparison, the 41.5 GHz and 23.2 GHz transitions have lower energy levels of approximately 33 K and approximately 41 K, respectively; and show absorption against the two star-forming SgrB2(N) hot cores with systematic LSR velocities of +64 (the LMH) and +82 kilometers per second. These ketenimine data show that the hot core at +82 kilometers per second is cooler than the hot core at +64 kilometers per second. Ketenimine is likely formed directly from its isomer methyl cyanide (CH3CN) by tautomerization driven by shocks that pervade the star-forming region.
The new interstellar molecules propenal (CH2CHCHO) and propanal (CH3CH2CHO) have been detected largely in absorption toward the star-forming region Sagittarius B2(N) by means of rotational transitions observed with the 100 m Green Bank Telescope (GBT) operating in the range from 18 GHz (λ ~ 1.7 cm) to 26 GHz (λ ~ 1.2 cm). The GBT was also used to observe the previously reported interstellar aldehyde propynal (HC2CHO) in Sagittarius B2(N), which is a known source of large molecules presumably formed on interstellar grains. The presence of these three interstellar aldehydes toward Sagittarius B2(N) strongly suggests that simple hydrogen addition on interstellar grains accounts for successively larger molecular species: from propynal to propenal and from propenal to propanal. Energy sources within Sagittarius B2(N) likely permit the hydrogen addition reactions on grain surfaces to proceed. This work demonstrates that successive hydrogen addition is probably an important chemistry route in the formation of a number of complex interstellar molecules. We also searched for but did not detect the three-carbon sugar glyceraldehyde (CH2OHCHOHCHO).
In this paper we show explicit and direct relations between the expected quantities and the observed quantities for the components of Galactic superluminal sources. Basic formulas for calculating the real speed and the angle to the line of sight of the components from the data of proper motions and the distance of the source are presented. We point out that the real speed and the angle to the line of sight of components can be uniquely and directly determined from the observed values of the proper motions and the distance of the source. It is not necessary to calculate an intermediate quantity first and then using the resulted value to calculate the two required quantities. The process of the calculation is simple, and in this way, some extra uncertainties are avoided.
This paper discusses the problem of the optimisation of the scanning strategy for the Planck mission.
We simulate Planck observations by adopting a detailed model of the microwave sky including monopole, dipole, anisotropies of the cosmic microwave background (CMB) and galactic and extragalactic foregrounds. We estimate the impact of main beam optical aberrations on CMB anisotropy measurements in presence of extragalactic source fluctuations and we discuss the main implications for the Planck telescope design. By analysing the dipole pattern, we quantify the Planck performance in the determination of CMB spectral distortion parameters in presence of foreground contaminations.
The VSA is an aperture synthesis array dedicated to measuring anisotropies in the Cosmic Microwave Background (CMB). It has observed in two configurations to measure the CMB power spectrum from l=150–1600, detecting the first three acoustic peaks at good signal-to-noise. We now plan to enhance the telescope to allow observation at higher l. This will allow measurement of the fourth and subsequent peaks and will allow us to break degeneracies that exist at present between cosmological parameters. In addition we will investigate the excess power detected by CBI at l > 2000 and will conduct high-sensitivity searches for topological defects.
We study the effect of Galactic foregrounds with spatially varying spectral indices on analysis of simulated data from the Planck Satellite. We also briefly mention the effect the extra-galactic point sources have on the data analysis and summarise the most recent constraints on Galactic emission at GHz frequencies.
Observations of the Cosmic Microwave Background (CMB), large scale structure (LSS) and standard candles such as Type 1a Supernovae (SN) each place different constraints on the values of cosmological parameters. We assume an inflationary Cold Dark Matter model with a cosmological constant, in which the initial density perturbations in the universe are adiabatic. We discuss the parameter degeneracies inherent in interpreting CMB or SN data, and derive their orthogonal nature. We then present our preliminary results of combining CMB and SN likelihood functions. The results of combining the CMB and IRAS 1.2 Jy survey information are given, with marginalised confidence regions in the H_0, Omega_m, b_IRAS and Q_rms-ps directions assuming n=1, Omega_Lambda+Omega_m=1 and Omega_b h^2=0.024. Finally we combine all three likelihood functions and find that the three data sets are consistent and suitably orthogonal, leading to tight constraints on H_0, Omega_m, b_IRAS and Q_rms-ps, given our assumptions.
We show how to take advantage of a circle scanning strategy, such as that planned for the Planck mission, to get rid of low frequency noises for polarised data.
Upcoming microwave background experiments will see an incredible increase in the volume of data to be analyzed, which makes the choice of how it is discretized on the sky a crucial issue. I discuss criteria for evaluating different pixelizations and the advantages of using an exactly azimuthal or ‘igloo’ pixelization of the sky. Talk given at “The CMB and the Planck Mission” workshop in Santander, Spain, June 1998.
In this paper I present three new results of astronomical interest concerning the theory of Abel inversion. (1) I show that in the case of a spatial emissivity that is constant on toroidal surfaces and projected along the symmetry axis perpendicular to the torus' equatorial plane, it is possible to invert the projection integral. From the surface (i.e., projected) brightness profile one then formally recovers the original spatial distribution as a function of the toroidal radius. (2) By applying the above-described inversion formula, I show that if the projected profile is described by a truncated off-center gaussian, the functional form of the related spatial emissivity is very simple and - most important - nowhere negative for any value of the gaussian parameters, a property which is not guaranteed - in general - by Abel inversion. (3) Finally, I show how a generic multimodal centrally symmetric brightness distribution can be deprojected using a sum of truncated off-center gaussians, recovering the spatial emissivity as a sum of nowhere negative toroidal distributions.
Gravitational interaction of cosmic microwave background (CMB) photons with matter perturbations present along the line-of-sight to the surface of last scattering modifies the shape of the CMB anisotropy power spectrum. Here I focus on (linear) integrated Sachs-Wolfe and (non-linear) gravitational lensing effects and discuss the detectability of the resulting distortions and their possible consequences for the CMB-based estimation of cosmological parameters. Specifically, I discuss if any of those effects may allow us to use CMB experiments to put independent constraints on the curvature of the universe and the cosmological constant, i.e. breaking the so-called geometrical degeneracy in CMB parameter estimation discussed by Bond, Efstathiou and Tegmark (1997) and Zaldarriaga, Spergel and Seljak (1997). I address that issue using the Fisher matrix approach and show that gravitational lensing of the CMB temperature and polarisation patterns might be detectable by the Planck Surveyor satellite, leading to useful independent and precise constraints on the cosmological constant and spatial curvature. The integrated Sachs-Wolfe effect though bound to restrict those parameters only very weakly still may set constraints more stringent than those currently available.
Basics on the continuous and discrete wavelet transform with two scales are outlined. We study maps representing anisotropies in the cosmic microwave background radiation (CMB) and the relation to the standard approach, based on the C-l's, is established through the introduction of a wavelet spectrum. We apply this technique to small angular scale CMB map simulations of size similar or equal to 12.8 degrees x 12.8 degrees and filtered with a 4'.5 Gaussian beam. This resolution resembles the experimental one expected for future high resolution experiments (e.g, the Planck mission), We consider temperature fluctuations derived from standard, open and flat-Lambda CDM models, We also introduce Gaussian noise (uniform and non-uniform) at different S/N levels and results are given regarding denoising.
We discuss the problem of constraining cosmological parameters with cosmic microwave background band--power estimates. Because these latter are variances, they do not have gaussian distribution functions and, hence, the standard $\chi^2$--approach is not strictly applicable. A general purpose approximation to experimental band--power likelihood functions is proposed, which requires only limited experimental details. Comparison with the full likelihood function calculated for several experiments shows that the approximation works well.
Planck LFI has four frequency channels. The two lower frequencies are 30 and 44 GHz. Jodrell Bank has worked with NRAO over a number of years and have developed a 30 GHz MIC amplifier which is approaching single figure noise temperatures when cooled to 20 K. We are currently constructing 20 such amplifiers and associated cryogenics and horns and waveguide transitions for the joint Jodrell Cambridge project: the very small array VSA. The amplifiers are robust to thermal cycling and are currently the very best state of the art. They use InP HEMTs and are thus ideal for Planck LFI. The Planck work is in collaboration with the IAC of Tenerife.
In this paper, we investigate if K-correction has strong impact on the alpha(ro) - alpha(ox) color-color diagram of BL Lacertae objects and obviously affects the classification of the objects. A sample consisting of the three kinds of the objects, those of low energy peaked BL Lacs (LBLs), high energy peaked BL Lacs (HBLs), and intermediate BL Lacs (IBLs), with all the values of radio, optical and X-ray fluxes and redshift available for the sources, is employed. We calculate the indices alpha(ro), alpha(ox) and alpha(rx) in both cases of K-correction and no K-correction and compare the results. The results show that: (1) for dividing BL Lacertae objects into three classes, LBLs, HBLs and IBLs, the effect of K-correction is negligible; (2) for classification, only a few of the objects may be affected by the effect.
Many questions originated when Comet Shoemaker-Levy 9 collided with Jupiter on July 1994 have been solved. However, quite a lot of them remain unexplained. Plumes and impact footprints were among the most spectacular consequences of the crash. We relate both features starting from two well measured observables: (1) center-to-edge distances on the impact sites and (2) times obtained from lightcurves. In this approach, only simple projectile equations have been used. An interesting result is found: an excellent linear correlation between the vertical velocity of the ejected material and the pre-impact fragment diameters. The apex of the ejected material was at 70 degrees above the horizontal, and the representative bulk material travelled on a 40 degrees trajectory.
In this paper, a computational technique to evaluate the parameters of moving clusters is established together with its error estimates in closed analytical forms. A general computational algorithm for these developments is proposed and applied to Hyades cluster. The data used are 60 stars selected from Schwan's Tables 1991 [7].
