We describe the performance of our latest generations of sensitive wide-band high-resolution digital fast Fourier transform spectrometer (FFTS). Their design, optimized for a wide range of radio ...astronomical applications, is presented. Developed for operation with the GREAT far infrared heterodyne spectrometer on-board SOFIA, the eXtended bandwidth FFTS (XFFTS) offers a high instantaneous bandwidth of 2.5 GHz with 88.5 kHz spectral resolution and has been in routine operation during SOFIA’s Basic Science since July 2011. We discuss the advanced field programmable gate array (FPGA) signal processing pipeline, with an optimized multi-tap polyphase filter bank algorithm that provides a nearly loss-less time-to-frequency data conversion with significantly reduced frequency scallop and fast sidelobe fall-off. Our digital spectrometers have been proven to be extremely reliable and robust, even under the harsh environmental conditions of an airborne observatory, with Allan-variance stability times of several 1000 s. An enhancement of the present 2.5 GHz XFFTS will duplicate the number of spectral channels (64k), offering spectroscopy with even better resolution during Cycle 1 observations.
Aims. The circumnuclear disk (CND) of the Galactic center is exposed to many energetic phenomena coming from the supermassive black hole Sgr A* and from stellar activities. These energetic activities ...can affect the chemical composition in the CND through interaction with UV photons, cosmic rays, X-rays, and shock waves. We aim to constrain the physical conditions present in the CND through chemical modeling of observed molecular species detected toward it. Methods. We analyzed a selected set of molecular line data taken toward a position in the southwest lobe of the CND with the IRAM 30m and APEX 12-m telescopes and derived the column density of each molecule via a large velocity gradient (LVG) analysis. The determined chemical composition is compared with a time-dependent, gas-grain chemical model based on the UCL_CHEM code,which includes the effects of shock waves with varying physical parameters. Results. We detect molecules, such as CO, HCN, HCO+, HNC, CS, SO, SiO, NO, CN, H2CO, HC3N, N2H+, and H3O+, and obtain their column densities. Total hydrogen densities obtained from LVG analysis range between 2 × 104 and 1 × 106cm-3 and most species indicate values around several × 105cm-3. These values are lower than those corresponding to the Roche limit, which shows that the CND is tidally unstable. The chemical models show good agreement with the observations in cases where the density is ~104cm-3, the cosmic-ray ionization rate is high, > 10-15s-1, or shocks with velocities > 40 km s-1 have occurred. Conclusions. Comparison of models and observations favors a scenario where the cosmic-ray ionization rate in the CND is high, but precise effects of other factors, such as shocks, density structures, UV photons, and X-rays from the Sgr A*, must be examined with higher spatial resolution data.
We present modeling of distributed
λ
/4 microwave kinetic inductance detectors (MKIDs) showing how electromagnetic cross coupling between the MKID resonators can occur at frequencies corresponding to ...the microwave readout signal (
∼
4–8 GHz). We then show system beam pattern measurements in the reimaged focal plane of a 72 detector array of lens–antenna coupled MKIDs at 850 GHz, which enables a direct measure of any residual optical crosstalk. With use of transmission line bridges we see no residual cross coupling between MKIDs and hence low crosstalk down to the
-
30 dB level, with near Gaussian shape (limited by reimaging optics) to
-
10 dB level.
The circumnuclear disk (CND) of the Galactic Center is exposed to many energetic phenomena coming from the supermassive black hole Sgr A* and stellar activities. These energetic activities can affect ...the chemical composition in the CND by the interaction with UV-photons, cosmic-rays, X-rays, and shock waves. We aim to constrain the physical conditions present in the CND by chemical modeling of observed molecular species detected towards it. We analyzed a selected set of molecular line data taken toward a position in the southwest lobe of the CND with the IRAM 30m and APEX 12-meter telescopes and derived the column density of each molecule using a large velocity gradient (LVG) analysis. The determined chemical composition is compared with a time-dependent gas-grain chemical model based on the UCL\_CHEM code that includes the effects of shock waves with varying physical parameters. Molecules such as CO, HCN, HCO\(^+\), HNC, CS, SO, SiO, NO, CN, H\(_2\)CO, HC\(_3\)N, N\(_2\)H\(^+\) and H\(_3\)O\(^+\) are detected and their column densities are obtained. Total hydrogen densities obtained from LVG analysis range between \(2 \times 10^4\) and \(1 \times 10^6\,\)cm\(^{-3}\) and most species indicate values around several \(\times 10^5\,\)cm\(^{-3}\), which are lower than values corresponding to the Roche limit, which shows that the CND is tidally unstable. The chemical models show good agreement with the observations in cases where the density is \(\sim10^4\,\)cm\(^{-3}\), the cosmic-ray ionization rate is high, \(>10^{-15} \,\)s\(^{-1}\), or shocks with velocities \(> 40\,\)km s\(^{-1}\) have occurred. Comparison of models and observations favors a scenario where the cosmic-ray ionization rate in the CND is high, but precise effects of other factors such as shocks, density structures, UV-photons and X-rays from the Sgr A* must be examined with higher spatial resolution data.
We use a recent policy change in the Netherlands to study how changes in search requirements for the older unemployed affect their transition rates to employment, early retirement and ...sickness/disability benefits. The reform, becoming effective on January 1 2004, requires the elderly to formally report their job search efforts to the employment office in order to avoid a (temporary) cut in benefits. Before the new law was passed, unemployed individuals were allowed to stop all search activity at the moment they turned 57.5. Estimating various duration models using difference-in-difference and regression discontinuity approaches, we find that for several groups of individuals who are affected by the policy change, the stricter search requirements significantly increases their entry rate into employment. However, we also find evidence of a higher outflow to sickness/disability insurance schemes, a presumably unwanted side-effect of the policy change.
► A Dutch policy change imposed job search requirements on the older unemployed (57.5+). ► We study transition rates to employment, early retirement and disability benefits. ► Difference-in-difference techniques and RD designs within a duration frame-work. ► Positive: Outflow to jobs increased by 6.5 percentage points. ► Negative: outflow to disability benefits increased by 2.5–4 percentage points.
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