Abstract
The designed practically prototype of an advanced acousto-optical radio-wave spectrometer is presented in a view of its application to investigating the Milky Way star formation problems. The potential areas for observations of the cold interstellar medium, wherein such a spectrometer can be exploited successfully at different approximations, are: 1) comparison of the Milky Way case with extragalactic ones at scale of the complete galactic disk; 2) global studies of the Galactic spiral arms; and 3) characterization of specific regions like molecular clouds or star clusters. These aspects allow us to suggest that similar instrument will be really useful. The developed prototype of spectrometer is able to realize multi-channel wideband parallel spectrum analysis of very-high-frequency radio-wave signals with an improved resolution power exceeding 103. It includes the 1D-acousto-optic wide-aperture cell as the input device for real-time scale data processing. Here, the current state of developing this acousto-optical spectrometer in frames of the astrophysical instrumentation is briefly discussed, and the data obtained experimentally with a tellurium dioxide crystalline acousto-optical cell are presented. Then, we describe a new technique for more precise spectrum analysis within an algorithm of the collinear wave heterodyning. It implies a two-stage integrated processing, namely, the wave heterodyning of a signal in an acoustically square-law nonlinear medium and then the optical processing in the same solid-state cell. Technical advantage of this approach lies in providing a direct multi-channel parallel processing of ultra-high-frequency radio-wave signals with the resolution power exceeding 104. This algorithm can be realized on a basis of exploiting a large-aperture effective acousto-optical cell, which operates in the Bragg regime and performs the ultra-high-frequency co-directional collinear acoustic wave heterodyning. The general concept and basic conclusions here are confirmed by proof-of-principle experiments with the specially designed cell of a new type based on a lead molybdate crystal.
Highlights
Research in star formation is a keystone topic in Astrophysics
The sites of star formation are normally “obscured” by the presence of material in those areas where stars are under formation, and this fact represents the major obstacle to improving our knowledge of the topic
The wide ranges for the above-mentioned physical parameters, which can be observed in the Milky Way and along its evolution, produce the question about the contrast needed to detect the IMF variations expected for a CMF in the stochastic model
Summary
Research in star formation is a keystone topic in Astrophysics. Decades of research in this field concluded that the stars are formed by a complex collapse process of the progenitor cloud, and modern models for the early formation inherent in clusters include detailed descriptions of the accretion at disk and chemical implications [1]. There are extended 24 μm sources that are resolved into stars in the Spitzer/IRAC bands (~2") Study of one such extended source surrounding the IRAS18236-1205 source, one of our 12 regions, would be able to spatially resolve this diffuse source into point sources, which would be analyzed to check whether they are the missing low-mass stars that are still in the process of formation. These data would present serious challenge to the present ideas regarding the formation of low-mass stars [22] All these processes require a high angular and spectral resolution from several hundreds of km\s in bandwidth and fractions of km\s in velocity resolution, equivalently at 200 GHz: a bandwidth of 500 MHz at resolution of 60 kHz, or higher spectral resolution: a bandwidth of 50 MHz and resolution of 5 kHz at variable angular resolution from arcminutes to sub-arcseconds, available with interferometers like ALMA [23]. Their performances are at given quality and compactness together with a low energy
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