Viktor V. Hristov

Measurements of Anisotropy in the Cosmic Microwave Background Radiation at 0.′5 Scales near the Stars HR 5127 and φ Herculis

We present measurements of cosmic microwave background (CMB) anisotropy near the stars HR 5127 and Herculis from the fifth flight of the Millimeter-wave Anisotropy eXperiment (MAX). We scanned 8° strips of the sky with an approximately Gaussian 05 FWHM beam and a 14 peak to peak sinusoidal chop. The instrument has four frequency bands centered at 3.5, 6, 9, and 14 cm-1. The IRAS 100 μm map predicts that these two regions have low interstellar dust contrast. The HR 5127 data are consistent with CMB anisotropy. The Herculis data, which were measured at lower flight altitudes, show time variability at 9 and 14 cm-1, which we believe to be due to atmospheric emission. However, the Herculis data at 3.5 and 6 cm-1 are essentially independent of this atmospheric contribution and are consistent with CMB anisotropy. Confusion from Galactic foregrounds is unlikely based on the spectrum and amplitude of the structure at these frequencies. If the observed HR 5127 structure and the atmosphere-independent Herculis structure are attributed to CMB anisotropy, then we find ΔT/T = l(l + 1)Cl/2π1/2 = 1.2+ 0.4−0.3 × 10-5 for HR 5127 and 1.9+ 0.7−0.4 × 10-5 for Herculis in the flat band approximation. The upper and lower limits represent a 68% confidence interval added in quadrature with a 10% calibration uncertainty.

The second measurement of anisotropy in the cosmic microwave background radiation at 0.°5 scales near the star μ Pegasi

During the fifth flight of the Microwave Anisotropy Experiment (MAX5), we revisited a region with significant dust emission near the star mu Pegasi. A 3.5 cm(-1) low-frequency channel has been added since the previous measurement (Meinhold et al. 1993a). The data in each channel clearly show structure correlated with IRAS 100 mu m dust emission. The spectrum of the structure in the 6, 9, and 14 cm(-1)channels is described by I-v proportional to nu(beta)B(nu) (T-dust),where beta = 1.3 and T-dust = 19 K and B-v is the Planck function. However, this model predicts a smaller amplitude in the 3.5 cm(-1) band than is observed. Considering only linear combinations of the data independent of the best-fit foreground spectrum for the three lower channels, we find an upper limit to CMBR fluctuations of Delta T/T =(C(l)l(l + 1)/2 pi)(1/2) less than or equal to 1.3 x 10(-5) at the 95 percent confidence level. The result is for a flat-band power spectrum and does not include a 10 percent uncertainty in calibration. It is consistent with our previous observation in the region.

Observation of forbidden C II 158 micron emission from the diffuse interstellar medium at high Galactic latitude

We report the first detection of forbidden C II 158 micron line emission from the diffuse interstellar medium at high Galactic latitude. We have measured the integrated line intensity in a 36 arcmin field of view along a triangular scan path in a 5 x 20 deg region in Ursa Major using a rocket-borne, liquid-helium-cooled spectrophotometer. The scan included high-latitude infrared cirrus, molecular clouds, a bright external galaxy, M82, and the H I Hole, which is a region of uniquely low neutral hydrogen column density. Emission from forbidden C II is observed in all regions, and, in the absence of appreciable CO emission, it is well correlated with neutral hydrogen column density. We observe a forbidden C II gas cooling rate which varies from (1.18 +/- 0.4 to 3.25 +/- 0.8) x 10 exp -26 ergs/s/H atom. Regions with CO emission have enhanced forbidden C II line emission over that expected from the correlation with neutral hydrogen column density. We measure a line-to-continuum ratio which varies from 0.002 to 0.008 in comparison with the all-sky average of 0.0082 reported by FIRAS, which is heavily weighted toward the Galactic plane.

A rocket-borne observation of the far-infrared sky at high Galactic latitude

We have measured the surface brightness of the far-infrared sky at lambda = 134, 154, and 186 micrometers at high Galactic latitude using a liquid-He-cooled, rocket-borne telescope. The telescope scanned over a 5 deg x 20 deg region which includes infrared cirrus, high-latitude molecular clouds, the starburst galaxy M82, and the H I Hole in Ursa Major, a region with uniquely low H I column density. The measured brightness at 134, 154, and 186 micrometers is well correlated with the 100 micrometers brightness measured by IRAS and, in regions excluding molecular clouds, with H I column density. The spectrum of the component correlated with H I is well fitted by a gray-body spectrum with a temperature of 16.4 (+2.3/-1.8) K, assuming an emissivity proportional to lambda-2. Assuming a constant far-infrared dust emissivity per hydrogen nucleus, the ratio of the H2 column density to the velocity-integrated CO intensity in the high-latitude molecular cloud is NH2/Wco = (1.6 +/- 0.3) x 1020/sq cm/(K km/s). The residual brightness after subtracting the emission correlated with H I column density is lambda Ilambda(154 micrometers) = (1.4 +/- 0.6) x 10-12 W/sq cm/sr, yielding an upper limit to the far-infrared extragalactic background radiation of lambda Ilambda(154 micrometers) is less than 2.6 x 10-12 W/sq cm/sr.

Compact low‐pass electrical filters for cryogenic detectors

We describe the design and performance of compact, low‐pass electrical filters, suitable for operation at cryogenic temperatures. The filters are two pole LC filters with a cutoff at ≊100 kHz, an attenuation of −24 dB/octave, and a stop band rejection of −80 dB between 5 and 20 MHz. Their function is to suppress rf voltage noise to sensitive cryogenic detectors. The low‐pass filters are realized using surface mounted devices on thin PC boards which can be stacked for maximum packing density. Compact modules containing 14 and 35 filters have been developed and installed in the Infrared Telescope in Space.We describe the design and performance of compact, low‐pass electrical filters, suitable for operation at cryogenic temperatures. The filters are two pole LC filters with a cutoff at ≊100 kHz, an attenuation of −24 dB/octave, and a stop band rejection of −80 dB between 5 and 20 MHz. Their function is to suppress rf voltage noise to sensitive cryogenic detectors. The low‐pass filters are realized using surface mounted devices on thin PC boards which can be stacked for maximum packing density. Compact modules containing 14 and 35 filters have been developed and installed in the Infrared Telescope in Space.

Integration and instrument characterization of the cosmic infrared background experiment 2 (CIBER-2)

The extragalactic background light (EBL) is the integrated emission from all objects outside of the Milky Way galaxy. Imprinted by the history of stellar emission, the EBL in the near infrared traces light back to the birth of the first stars in the Universe and can allow tight constraints on structure formation models. Recent studies using data from the Spitzer Space Telescope and the first Cosmic Infrared Background ExpeRiment (CIBER-1) find that there are excess fluctuations in the EBL on large scales which have been attributed to either high redshift galaxies and quasars, or to stars that were stripped from their host galaxies during merging events. To help disentangle these two models, multi-wavelength data can be used to trace their distinctive spectral features. Following the success of CIBER-1, CIBER-2 is designed to identify the sources of the EBL excess fluctuations using data in six wavebands covering the optical and near infrared. The experiment consists of a cryogenic payload and is scheduled to launch four times on a recoverable sounding rocket. CIBER-2 has a 28.5 cm telescope coupled with an optics system to obtain wide-field images in six broad spectral bands between 0.5 and 2.5 μm simultaneously. The experiment uses 2048 × 2048 HAWAII-2RG detector arrays and a cryogenic star tracker. A prototype of the cryogenic star tracker is under construction for a separate launch to verify its performance and star tracking algorithm. The mechanical, optical, and electrical components of the CIBER-2 experiment will have been integrated into the payload by mid-2018. Here we present the final design of CIBER-2 and our team’s instrument characterization efforts. The design and analysis of the optical focus tests will be discussed. We also report on the performance of CIBER-2 support systems, including the cooling mechanisms and deployable components. Finally, we outline the remaining tasks required to prepare the payload for launch.

Development of data storage system and GSE for cosmic infrared background experiment 2 (CIBER-2)

Cosmic Infrared Background ExpeRiment-2 (CIBER-2) is an international project to make a rocket-borne measurement of the Cosmic Infrared Background (CIB) using three HAWAII-2RG image sensors. Since the rocket telemetry is unable to downlink all the image data in real time, we adopt an onboard data storage board for each sensor electronics. In this presentation, the development of the data storage board and the Ground Station Electronics (GSE) system for CIBER2 are described. We have fabricated, integrated, and tested all systems and confirmed that all work as expected, and are ready for flight.

A rocket-borne observation of diffuse far-infrared emission from interstellar dust

We report observations of diffuse far‐infrared emission from interstellar dust at high Galactic latitudes using a rocket‐borne, liquid‐helium cooled telescope and photometer. The photometer has 5 spectral bands ranging from 90 μm to 190 μm with 0.5°∼0.65°FWHM fields‐of‐view. The detectors, stressed and unstressed Ge:Ga photoconductors, were cooled to 1 K and coupled to charge integrating amplifiers to achieve high sensitivity. We observed regions near Ursa Major including infrared cirrus, high latitude molecular clouds, and the HI hole, a region of uniquely low neutral hydrogen column density. Preliminary analysis shows a strong correlation of the emission at 134, 154, and 186 μm with 100 μm IRAS data.