The optical night sky at low surface brightness: High-latitude dust and faint field galaxies

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1989

OSTI ID:5051241

Guhathakurta, P

Deep CCD imaging in U, B{sub J}, R, and I, over angular scales ranging from a few arcseconds to over 30 arcminutes, is used to study two classes of astronomical objects that produce fluctuations in the dark night sky background: (1) interstellar dust clouds at high Galactic latitudes, initially identified by their thermal re-radiation of ambient starlight as IRAS 100 {mu}m cirrus; and (2) a population of faint blue field galaxies, which, at 30 B{sub J} mag arcsec{sup {minus}2}, begin to fill up the field of view. A CCD mosaicing technique, designed to allow imaging of large areas of the sky at low light levels, has been used to study the cirrus morphology. The scattering and re-emission of optical radiation from the cirrus are investigated, with the goal of learning more about the environment of these clouds and the physical processes involved. The cirrus is extremely red in both B{sub J}-R and R-I, much redder than a simple scattering model predicts. The excess R and I band flux is probably the result of luminescence in small hydrogenated dust grains. This very red color appears to be a universal signature of optically thin dust clouds at high latitudes, and should enable them to be distinguished from the second component, aggregates of faint blue galaxies. These galaxies dominate the number counts in the field, and the U band count slope is even steeper than that in B{sub J}. The colors, over the wavelength range 3,600 {angstrom}-1 {mu}m, are indicative of fairly recent evolution. The observed U-B{sub J} colors place an upper limit of z = 3 on the majority of these galaxies, unless they have an extremely (almost unreasonably) small Lyman break. A model for the evolution of field galaxies is developed, incorporating preferential brightening of present day dwarfs, and using the observed mass currently locked up as stars in a galaxy to constrain the galaxy's lifetime.

• Research Organization: Princeton Univ., NJ (United States)
• OSTI ID: 5051241
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BRIGHTNESS
CHARGE-COUPLED DEVICES
COLOR
COSMIC DUST
DUSTS
ELECTROMAGNETIC RADIATION
GALACTIC EVOLUTION
GALAXIES
IMAGES
INTERSTELLAR GRAINS
INTERSTELLAR SPACE
MATHEMATICAL MODELS
MORPHOLOGY
NIGHT SKY
OPTICAL PROPERTIES
ORGANOLEPTIC PROPERTIES
PARTICLES
PHYSICAL PROPERTIES
RADIATIONS
SCATTERING
SEMICONDUCTOR DEVICES
SKY
SPACE
VISIBLE RADIATION