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UV Insights Into Two Classes of Type Ia Supernovae

UV Insights Into Two Classes of Type Ia Supernovae

[Note added April 19: Tom Beal of the Arizona Daily Star has written a nice article HERE with extensive quotations from Nick Suntzeff of Texas A&M, and others.]

Peter Milne of Steward Observatory, Gautham Narayan of NOAO and UA, and collaborators Ryan Foley and Peter Brown have discovered two types of nearby Type Ia supernovae. These sub-classes of Ia supernova mostly differ in their UV-light output. They are called UV-red and UB-blue: the UV-red objects dominate locally. At high redshift, the UV-blue objects dominate. The optical colors also subtly change, leading to a possible misinterpretation, using the regular analysis, of the reddening and distance to the supernova. This change of type of supernova with the age of the Universe at time of explosion has implications for the fundamental parameters of cosmology, since the identical objects are not being compared as astronomers look farther away into the Universe. There is a distance error as a function of redshift, which will change the derivation of the cosmological parameters. While the observational underpinnings of the need for dark energy will not disappear, the precise values of the cosmological parameters, including the amount of dark energy, will change, probably at a low level. Theoretical models of supernovae will need to explain these observations.

Milne's analysis depended heavily upon the use of the Swift space telescope for the discovery of the UV properties of supernovae, on spectra from the Keck, VLT, and Gemini telescopes for the medium redshift sample, and on imaging from HST. The UA Press Release can be found HERE, and the two papers can be found HERE and HERE.
Laying of the First Stone for LSST

Laying of the First Stone for LSST

Suzanne Jacoby of LSST announces: "April 14, 2015 - LSST marks a major milestone today, with the traditional First Stone (Primera Piedra) ceremony taking place this afternoon on Cerro Pachón, Chile. While site leveling has already begun, laying of the first stone is a Chilean tradition marking the construction start for a new astronomical observatory. Chilean President Michelle Bachelet, U.S. Ambassador to Chile Michael A. Hammer, NSF Director France Córdova, and Charles Simonyi are among the dignitaries present to mark this start of summit construction. After a pause for today's festivities, the summit returns to being an active construction site under the direction of the LSST summit facility general contractor, Besalco. You can watch construction progress through our webcams, available at
Suzanne Jacoby, for the LSST Project Office"

Photo Credit: LSST Construction Webcam

Searching Back in Space for Galaxy Proto-Clusters

Using Steward and space observatories, Steward Observatory Assistant Astronomer Brenda Frye and former Steward Astronomer Hervé Dole have discovered vast complexes of galaxies in the distant universe. Galaxies such as our own Milky Way are usually found near other galaxies in groups or in some cases even in large clusters of galaxies. The galaxy clusters we see today tend to have only older, less active galaxies. Understanding the puzzle of how these galaxy clusters formed and evolved into the relative state of retirement at this present time in cosmic history is a key question in cosmology. Now, using the Planck satellite’s unique ability to produce an all-sky survey of the universe (instead of looking at just one patch of sky as with a ground-based telescope), Frye and collaborators are able to find the earliest examples of these extremely rare and massive galaxy clusters. What is interesting is that all the galaxies in these ‘baby clusters’ are forming stars at the same time, similar to what happens when one plugs in the Christmas lights and the tree gets suddenly bright. It appears that the galaxies in these clusters are not pacing themselves as one would aim to do in a marathon, but rather are using up a substantial amount of energy at the beginning of the race. They ‘turn on’ their Christmas lights all at once, and then later run out of fuel. In a handful of cases they found only a single extremely bright galaxy instead of a whole cluster of galaxies. Frye explains, “This is odd as a single galaxy should not be bright enough to see even with Planck. Understanding how one galaxy can be detected is one of the mysteries that is being solved here at UA”. The answer appears to be that these objects are seen through natural telescopes in space in addition to being seen by Planck. “These natural telescopes take the form of entirely unrelated galaxy clusters near to Earth which bend the light of these distant sources.” Frye observes these special cases with such ground-based telescopes such as the Large Binocular Telescope and the MMT to learn more about these new and enigmatic objects.

A press release can be found HERE and a similar popular article can be found HERE.

Most Luminous Quasar in Early Universe

Most Luminous Quasar in Early Universe

An international team, led by astronomers at Peking University of China, and Steward Observatory, including Regents' Professor Xiaohui Fan, visiting graduate students Feige Wang and Jinyi Yang, assistant astronomer Ian McGreer and LBTO support astronomer David Thompson, have discovered the most luminous quasar yet known in the early Universe. This quasar, at a redshift of 6.3, or a distance of 12.8 billion lightyears, is powered by a supermassive black hole with an estimated mass of twelve billion solar masses. The existence of such massive black holes in the early universe posts significant challenges to the theory of black hole growth and its relation to galaxy evolution. The team used Steward facilities, including MMT, LBT and Magellan, for the measurements of quasar distance and the mass of the black hole.

The UANews article can be found HERE. A sky&Telescope article can be found HERE. And now a CNN article can be found HERE. And for a short while, it's one of the four revolving front-page stories at the UA Homepage.

Decker French named ARCS Foundation Scholar

Graduate Student Decker French has been named of of 17 ARCS Foundation Scholars for 2015-2016. She will receive her award and stipend and travel grant on April 17. for more information, go HERE. We join Steward Dept. Head Buell Jannuzi in congratulating Decker.

Announcing the 18th Marc Aaronson Memorial Lecturer

Announcing the 18th Marc Aaronson Memorial Lecturer

The Aaronson Committee has met, and it's our pleasure to announce that our 18th Marc Aaronson Memorial Lecturer is Vasily Belokurov of the Institute of Astronomy, in Cambridge, UK. Buell Jannuzi has telephoned Dr. Belokurov, and Dr. Belokurov has accepted with great pleasure. We are shooting for a Fall 2015 talk.

Dr. Belokurov is cited for his long-term work on discovery of Milky Way dwarf galaxies, on being astronomy's premier data miner, for his work on star streams culminating in the Field of Streams, for his work (with students) on the structure and size and density distribution of the Milky Way from BHB stars, on discovering gravitational lenses in the Cassowary Survey, and on data mining to discover metal-poor dIrr galaxies from SDSS imaging (with MMT followup). To put things in perspective, of the sixteen or so ultra-faint galaxies orbiting the Milky Way, Dr. Belokurov has been on the discovery papers of ~10 (mostly as first or second author).

You can learn more about this award in the paragraph below and at

The Marc Aaronson Memorial Lectureship was established to honor our Steward Observatory colleague who died tragically in 1987 at the age of 36. In his spirit, we honor an individual, within 15 years of the PhD, who by his or her passion for research and dedication to excellence, during the ten years preceding the award, has produced a body of work in observational astronomy which has resulted in a significant deepening of our understanding of the universe." [Since Marc was 10 years past his PhD at his death and had already been on the cover of Time Magazine, a few years ago we changed the rules to guarantee a younger person.]


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