Neutral hydrogen in galactic clusters

Observations of the neutral hydrogen content of the galactic clusters h and χ Persei, the Pleiades, the cluster in Coma Berenices, Praesepe, and M 67 have been made with the Harvard College Observatory 60-foot radio telescope. The receiver used was the original receiver made by the Ewen Knight Corporation for the Harvard 24-foot radio telescope. The observations were of three kinds: (1) right-ascension drift curves at 50 kc/s bandwidth, with the receiver fixed-tuned to the frequency of maximum cluster emission, if known, or to the frequency given by the cluster optical radial velocity; (2) conventional frequency profiles at the position of maximum cluster radiation; (3) “residual” frequency profiles, where there is significant general galactic radiation at the cluster frequency and position. These data provide the spatial distribution of any H i in the cluster vicinity that is in excess of the general galactic H i, and a frequency profile for this excess hydrogen. Any excess H i found is considered associated with the cluster if it agrees in velocity and position with the optical cluster.

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Hydrogen Content of Young Stellar Clusters. I. Methods of Observation and Reduction

Australian Journal of Physics ◽

10.1071/ph730829 ◽

1973 ◽

Vol 26 (6) ◽

pp. 829 ◽

Cited By ~ 6

Author(s):

HM Tovmassian

Keyword(s):

Radio Telescope ◽

Hydrogen Content ◽

Data Reduction ◽

Neutral Hydrogen ◽

Hydrogen Gas ◽

Continuum Emission ◽

Stellar Clusters ◽

Hydrogen Line ◽

Galactic Clusters

Observations of 16 open galactic clusters in their continuum emission and at the neutral hydrogen line have been made with the Parkes 64 m radio telescope in an attempt to determine the total amount of hydrogen gas associated with them. In this, the first of a series of five papers, the observing procedure and the method of data reduction are described.

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Results in Right Ascension of Observations of 156 Fundamental Stars observed with the Meridian-Circle of Harvard College Observatory

Astronomische Nachrichten ◽

10.1002/asna.18720801302 ◽

1873 ◽

Vol 80 (13) ◽

pp. 193-206

Author(s):

Joseph Winlock

Keyword(s):

Meridian Circle ◽

Harvard College ◽

Harvard College Observatory ◽

Right Ascension

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Some comments about observations and image processing of comet 29P/Schwassmann-Wachmann 1

International Astronomical Union Colloquium ◽

10.1017/s0252921100031493 ◽

1999 ◽

Vol 173 ◽

pp. 243-248

Author(s):

D. Kubáček ◽

A. Galád ◽

A. Pravda

Keyword(s):

Image Processing ◽

Large Scale ◽

Harvard College ◽

Oak Ridge ◽

Large Scale Structures ◽

Short Period Comet ◽

Short Period ◽

Scale Structures ◽

Harvard College Observatory ◽

Period Comet

AbstractUnusual short-period comet 29P/Schwassmann-Wachmann 1 inspired many observers to explain its unpredictable outbursts. In this paper large scale structures and features from the inner part of the coma in time periods around outbursts are studied. CCD images were taken at Whipple Observatory, Mt. Hopkins, in 1989 and at Astronomical Observatory, Modra, from 1995 to 1998. Photographic plates of the comet were taken at Harvard College Observatory, Oak Ridge, from 1974 to 1982. The latter were digitized at first to apply the same techniques of image processing for optimizing the visibility of features in the coma during outbursts. Outbursts and coma structures show various shapes.

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Photographic Study of Stellar Spectra, Harvard College Observatory

Scientific American ◽

10.1038/scientificamerican07091887-9603supp ◽

1887 ◽

Vol 24 (601supp) ◽

pp. 9603-9604

Keyword(s):

Harvard College ◽

Stellar Spectra ◽

Harvard College Observatory

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A Low frequency Southern Sky Survey Using the Mauritius Radio Telescope

Symposium - International Astronomical Union ◽

10.1017/s0074180900168494 ◽

2002 ◽

Vol 199 ◽

pp. 25-31

Author(s):

N. Udaya Shankar

Keyword(s):

Radio Telescope ◽

Low Frequency ◽

Fourier Synthesis ◽

North East ◽

The North ◽

Sky Survey ◽

Correlation Receiver ◽

Complex Correlation ◽

Right Ascension ◽

East West

The Mauritius Radio Telescope (MRT) is a Fourier synthesis instrument which has been built to fill the gap in the availability of deep sky surveys at low radio frequencies in the southern hemisphere. It is situated in the north-east of Mauritius at a southern latitude of 20°.14 and an eastern longitude of 57°.73. The aim of the survey with the MRT is to contribute to the database of southern sky sources in the declination range −70° ≤ δ ≤ −10°, covering the entire 24 hours of right ascension, with a resolution of 4' × 4'.6sec(δ + 20.14°) and a point source sensitivity of 200 mJy (3σ level) at 151.5 MHz.MRT is a T-shaped non-coplanar array consisting of a 2048 m long East-West arm and a 880 m long South arm. In the East-West arm 1024 fixed helices are arranged in 32 groups and in the South arm 16 trolleys, with four helices on each, which move on a rail are used. A 512 channel, 2-bit 3-level complex correlation receiver is used to measure the visibility function. At least 60 days of observing are required for obtaining the visibilities up to the 880 m spacing. The calibrated visibilities are transformed taking care of the non-coplanarity of the array to produce an image of the area of the sky under observation.This paper will describe the telescope, the observations carried out so far, a few interesting aspects of imaging with this non-coplanar array and present results of a low resolution survey (13' × 18') covering roughly 12 hours of right ascension, and also present an image with a resolution of 4' × 4'.6sec(δ + 20.14°) made using the telescope.

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