摘要:

TheseProceedingsculminate an exciting year of brainstorming, collaborating, and communicating. Our primary aim for the “UV Universe” conference was to bring together researchers of the local and remote universe with the hope that the two cultures would gain new insights on the evolution of galaxies and the intergalactic medium (IGM) through cosmic time. The UV theme came from the fact that recent deep views of extremely distant galaxies are revealing restframe UV emission that has been redshifted into the visible spectrum. By comparing the UV properties of local galaxies and the IGM with the restframe UV properties of their high-redshift counterparts, we hoped to address whether or not there is compelling evidence for significant evolution of galaxies over the last 10–15 billion years. Fortunately, the conference itself evolved over a much shorter timescale. The following are some recollections along the way. ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.53763

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Sung (with the usual apologies) to the tune of “Blue Moon.” ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.53772

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The vacuum ultraviolet offers a unique perspective on galaxy morphology, stellar populations, and interstellar material which is of particular relevance to interpreting high redshift galaxies and the history of cosmic star formation. Here we review UV imaging studies of galaxies since 1990. ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.53740

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Ultraviolet (UV) images of nearby star-forming galaxies obtained with the Faint Object Camera aboard the Hubble Space Telescope (HST) reveal that the starburst regions in these objects are composed of numerous bright, compact knots of hot stars superposed on a diffuse, extended background. I present several examples ofHSTUV images of these regions in various galaxies and discuss the properties of the starburst knots and the diffuse background, as well as the implications for the star-formation histories in these objects. I briefly compare the UV images of these starburst regions with images obtained at longer wavelengths. Finally, I use these UV images to construct simulated observations of starburst galaxies at high-redshift and compare the results with recent images of high-redshift objects. ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.53773

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Our recent work on starbursts, particularly in the ultraviolet (UV), is summarized. The intrinsic UV fluxes of UV selected starbursts can be derived from UV data alone because, to first order, their dust behaves like a foreground screen. This allows a comparison of the bolometric effective surface brightnessSeof UV selected starbursts to other starburst samples. Starbursts have a robust (90th percentile) upper limitSe≲2.0×1011L⊙ kpc−2,which strongly suggests that their global star formation intensities are regulated. The mechanism(s) involved in the regulation are not yet clear. The dust attenuation corrections for high-zstarbursts are significant. Calculations of the rate of evolution in the early universe based on zero dust interpretations are probably underestimated by about an order of magnitude. Hence the early universe was not quiescent, but obscured. ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.53774

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The Ultraviolet Imaging Telescope (UIT) was flown as part of theAstroObservatory on the Space ShuttleColumbiain December 1990 (see Figure 1) and again on the Space ShuttleEndeavourin March 1995. Ultraviolet (1200–3300 Å) images of a wide variety of astronomical objects were detected with UV image intensifiers and recorded on photographic film. Typical angular resolutions were 2–3 arcsec over a 40 arcmin field of view. The reduced and calibrated images from the first flight are available to the astronomical community through the National Space Science Data Center (NSSDC); the data recorded during the second flight will soon be available as well. UIT’s design, operation, data reduction, and calibration are described in detail in Stecher &etal; (1997), including a comprehensive description of the data characteristics. This publication provides UIT data users with information for understanding and using the data, as well as guidelines for analyzing other astronomical imagery made with image intensifiers and photographic film. Further information on theAstromissions and the UIT science program is available at the following websitehttp://fondue.gsfc.nasa.gov/UIT/UIT_HomePage.htmland in an educational slideset that is available from the Astronomical Society of the Pacific (Waller & Offenberg 1994). ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.53775

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Deep high-resolution imaging of galaxies at high-redshift has revealed a remarkable diversity of emission structures in the restframe ultraviolet. To better understand these remote and primeval realms, it is important to compare them with UV-emitting counterparts in the local universe. As part of two Spacelab/Astromissions, the Ultraviolet Imaging Telescope (UIT) has obtained wide-field (40-arcmin), well-resolved (3 arcsec) images of∼50nearby galaxies in the vacuum ultraviolet. Followup groundbased imaging at UBVRI and H&agr; bands has been completed for most of the well-resolved galaxies. Analysis of a small subset of these galaxies has revealed strong variations in the emission morphologies as a function of restframe wavelength. In the present study, we compare the UV morphologies of barred and unbarred spiral galaxies as a function of Hubble type and absolute luminosity. Radial extents are measured relative to their visible counterparts, and characteristic UV emission structures are identified (e.g. rings, bars, bi-symmetric hotspots, crooked-arms, etc). Morphological UV indicators for classifying the galaxies within the traditional Hubble sequence are explored. ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.53776

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Optical surveys for high-redshift(z∼2–5)star forming galaxies will preferentially identify UV-bright systems since the observed optical emission corresponds to the rest-frame UV. Studies of nearby UV-bright starbursts thus provide a unique opportunity to obtain a detailed understanding of the phenomena observed at high redshifts. We discuss the far-ultraviolet (FUV;&lgr;∼1500 Å) properties of the nearby blue starburst galaxy NGC 3310. The FUV morphology is compared to that observed at longer wavelengths. The stellar content of selected star forming regions is also discussed. ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.53777

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The UVISI suite of nine instruments (four imagers and five spectrographic imagers) was launched on the MSX spacecraft in April, 1996. During the months since launch the UVISI instruments have gathered a substantial amount of data over selected portions of the sky. We present UV observations of several extended galaxies taken with the UVISI instruments. Extended galaxies were observed with the UV imagers and the spectrographic imagers as part of the Celestial Backgrounds experiment. In this presentation we will report on observations of the Magellanic Clouds, M33, and M83. These galaxies were observed with the UV imagers and the spectrographic imagers (SPIMs). The narrow field UV image used a filter which covers 1800 to 3000 Å. The data from the five SPIMs continuously covers the wavelength range 1100 to 9000 Å during one set of observations. ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.53778

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Ultraviolet continuum and H&agr; fluxes measure two critical spectral regions of the emission from hot stars in galaxies. H&agr; indirectly measures the Lyman continuum’s ionizing flux, while the 1400 Å–3200 Å band, such as that imaged by the Ultraviolet Imaging Telescope (UIT), directly measures non-ionizing flux produced by O, B and A-type stars. The ratio of the two gives a “color” which is extremely sensitive to the age of the young stellar populations: model spectral energy distributions show that the ratio of Lyman continuum photon flux to the UIT 1520 Å bandpass flux decreases monotonically by a factor of 100 during the first 10 Myr of cluster evolution. We compare the ultraviolet morphology of the Magellanic Clouds, from the UIT and a rocket-borne wide-field UIT predecessor, with H&agr; morphology derived from the “Parking Lot Camera” images made by Bothun and Thompson (1988). In the LMC, the 30 Doradus region stands out as a region of large H&agr;/UV sandwiched between two regions with much smaller H&agr;/UV. The Shapley III constellation has UV-bright components (e.g the “fleur-de-lis”) but very little H&agr;. In the SMC, evolutionary extremes are suggested by the UV-bright clusters NGC 330 (nearly H&agr;-free) and NGC 346 (surrounded by a bright HII region). We present “color” images in the H&agr;/UV ratio for the entire LMC and most of the SMC bar. We interpret the images, compare them with other data, and discuss their implications for recent star formation, on large and small scales, in the Magellanic Clouds. ©1997 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.53779

出版商:AIP    

年代:1997

数据来源: AIP