ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Astronomy  (2)
  • Astrophysics  (1)
  • 1
    Publication Date: 2019-07-17
    Description: Studies of nearby spiral galaxies suggest that photodissociation regions (PDRs) are capable of producing the observed large--scale distribution of HI (Allen et al.- 1997, and references therein). The column density of HI in a PDR is fundamentally linked to the amount of far--ultraviolet (FUV) emission produced by nearby young stars and the local molecular gas volume density. Measurements of the HI column density and the FUV emission associated with PDRs thus provide a new probe of the molecular gas distribution in nearby galaxies. Advantages of this method include its insensitivity to assumptions about the CO/{\rm H2} conversion factor or the gas temperature. We discuss the application of this method to M101. The HI column density and FUV emission have been measured for 35 PDRs from VLA data (Braun 1997) and Ultraviolet Imaging Telescope data (Waller et al.-1997). We derive volume densities ranging from n-100 {\rm cm(exp -3)} in the central HI--poor regions of M101 to n -3000 {\rm cm(exp -3)} in the HI--rich periphery of the galaxy.
    Keywords: Astrophysics
    Type: Between the Stars II: The ISM, Galactic and Extragalactic Display (Session 71); May 30, 1999 - Jun 03, 1999; Chicago, IL; United States
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Publication Date: 2019-07-13
    Description: Observations of the sky background obtained with the Faint Object Spectrograph during 1991-1992 are discussed. Sky light can be an important contributor to the observed count rate in several of the instrument configurations especially when large apertures are used. In general, the sky background is consistent with the pre-launch expectations and showed the expected effects of zodiacal light and diffuse galactic light. In addition to these sources, there is, particularly during the daytime, a highly variable airglow component which includes a number of emission lines. The sky background will have an impact on the reduction and possibly the interpretation of some spectra.
    Keywords: Astronomy
    Type: NASA-CR-204004 , NAS 1.26:204004 , SPIE Proceedings Series; 1945; 232-243|Space Astronomical Telescopes and Instruments 2; Apr 13, 1993 - Apr 14, 1993; Orlando, FL; United States
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Publication Date: 2019-07-19
    Description: The Space Telescope Imaging Spectrograph (STIS) was installed in the Hubble Space Telescope (HST) in February of 1997, and operated until August of 2004, when an electrical malfunction in a power supply forced cessation of operations. On May 17,2009, during the fourth EVA of SM4, astronauts Michael Good and Mike Massimino undertook an eight-hour spacewalk, during which they replaced the STIS LVPS-2 circuit board containing the failed component, successfully repairing STIS. We will review the scientific capabilities and operational status of STIS after this repair. In most respects, STIS after the 2009 repair operates in much the same way as it did prior to the 2004 failure. Most changes in performance are close to what had been expected. The degradation of the STIS CCD due to radiation damage and the modest changes in optical throughput are consistent with extrapolation of previously-observed trends. Internal and external alignments of the instrument are also similar to what they were in 2004. The biggest surprise is that the dark current for the NUV MAMA detector is several times larger than had been expected and is only slowly decreasing towards its expected range. We discuss how these changes will affect science with STIS now and in the future.
    Keywords: Astronomy
    Type: 215th American Astronomical Society Conference; Jan 03, 2010 - Jan 07, 2010; Washington, DC; United States
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...