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Observations of High Galactic Latitude Line and Continuum Emission (912 - 1600 Å) with New Horizons
Jayant Murthy, James Overduin, Seth Redfield +5
We present observations of the cosmic ultraviolet background (CUVB) from 912 - 1600 A using the Stem aperture of the Alice spectrograph on the New Horizons spacecraft at 56 AU from…
High-S/N Quasar Observations with HST/COS: Deep Fields for Spectroscopy
Andrew J. Fox, Jerry Kriss, Philipp Richter +49
Hubble is still in prime observing condition for making transformative discoveries in UV astronomy. In this white paper we describe the science case for a deep (S/N>30) UV spectros…
Closing the UV Gap: Rest-frame EUV science from high-redshift QSOs as a legacy-defining capability
Rongmon Bordoloi, J. Michael Shull
The Hubble Space Telescope is the only high-resolution ultraviolet spectroscopic facility that will exist until the Habitable Worlds Observatory (HWO) achieves first light in the m…
Ionization Sources of the Local Interstellar Clouds: Two B-stars, Three White Dwarfs, and the Local Hot Bubble
J. Michael Shull, Rachel M. Curran, Michael W. Topping +1
The dominant sources of photoionizing radiation in the extreme ultraviolet (EUV) incident on the exterior of the local interstellar clouds include two nearby early B-type stars, $ε…
Quasar Spectral Energy Distributions in the Rest-Frame EUV: Hubble-COS Spectra of Two Ultra-luminous Quasars
J. Michael Shull, Rongmon Bordoloi, Charles W. Danforth
Using the Cosmic Origins Spectrograph (COS) aboard the Hubble Space Telescope with both far-UV (FUV) and near-UV (NUV) gratings, we measure the ionizing spectra of two bright, inte…
Beta Canis Majoris: The Other Major Ionization Source of the Local Interstellar Clouds
J. Michael Shull, Rachel M. Curran, Michael W. Topping
Two nearby B-type stars, CMa ( pc) and CMa ( pc), are important contributors to the photoionization of the local interstellar clouds. At spectral type B1…
The Lyman alpha Sky as Observed by New Horizons
G. R. Gladstone, J. M. Shull, W. R. Pryor +22
During September 2023 the Alice ultraviolet spectrograph on the New Horizons (NH) spacecraft was used to map diffuse Lyman alpha (Lya) emission over most of the sky, at a range of…
Excess Ultraviolet Emission at High Galactic Latitudes: A New Horizons View
Jayant Murthy, J. Michael Shull, Marc Postman +11
We present new observations of the cosmic ultraviolet background (CUVB) at high Galactic latitudes (), made using the Alice UV spectrograph on board the New Horiz…
Epsilon Canis Majoris: The Brightest EUV Source with Surprisingly Low Interstellar Absorption
J. Michael Shull, Rachel M. Curran, Michael W. Topping
The B2 star CMa, at parallax distance ~pc, dominates the H I photoionization of the local interstellar cloud (LIC). At its closer parallax distance compared to pre…
Characterizing the Circumgalactic Medium of Nearby Galaxies with HST/COS and HST/STIS Absorption-Line Spectroscopy: II. Methods and Models
Brian A. Keeney, John T. Stocke, Charles W. Danforth +6
We present basic data and modeling for a survey of the cool, photo-ionized Circum-Galactic Medium (CGM) of low-redshift galaxies using far-UV QSO absorption line probes. This surve…
HST-COS Observations of AGNs. III. Spectral Constraints in the Lyman Continuum from Composite COS/G140L Data
Evan M. Tilton, Matthew L. Stevans, J. Michael Shull +1
The rest-frame ultraviolet (UV) spectra of active galactic nuclei (AGNs) are important diagnostics of both accretion disk physics and their contribution to the metagalactic ionizin…
Tracing the Cosmic Metal Evolution in the Low-Redshift Intergalactic Medium
J. Michael Shull, Charles. W. Danforth, Evan M. Tilton
Using the Cosmic Origins Spectrograph aboard the Hubble Space Telescope, we measured the abundances of six ions (C III, C IV, Si III, Si IV, N V, O VI) in the low-redshift (z < 0.4…
HST-COS Observations of AGN. II. Extended Survey of Ultraviolet Composite Spectra from 159 Active Galactic Nuclei
Matthew L. Stevans, J. Michael Shull, Charles W. Danforth +1
The ionizing fluxes from quasars and other active galactic nuclei (AGN) are critical for interpreting their emission-line spectra and for photoionizing and heating the intergalacti…
Constraining UV Continuum Slopes of Active Galactic Nuclei With CLOUDY Models of Broad Line Region EUV Emission Lines
Joshua Moloney, J. Michael Shull
Understanding the composition and structure of the broad-line region (BLR) of active galactic nuclei (AGN) is important for answering many outstanding questions in supermassive bla…