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BDanielMayfield
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Re: Can we see neutrinos from ... ?

Postby BDanielMayfield » Fri Apr 14, 2017 6:50 pm

Since neutrinos are nearly impossible to detect how can the origin (the direction they come from) of the very few that are detected be determined?

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Chris Peterson
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Re: Can we see neutrinos from ... ?

Postby Chris Peterson » Fri Apr 14, 2017 7:08 pm

BDanielMayfield wrote:Since neutrinos are nearly impossible to detect how can origin (the direction they come from) of the very few that are detected be determined?

When neutrinos are associated with a transient or intermittent source, the signal rises above the background rate. If you have two or more widely separated detectors, you can correlate those peaks (looking at arrival time) and determine a direction. In the case of steady sources which add to the background, you can statistically correlate all arrival times at one station with those from another and identify source directions.
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BDanielMayfield
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Re: Can we see neutrinos from ... ?

Postby BDanielMayfield » Fri Apr 14, 2017 7:45 pm

Chris Peterson wrote:
BDanielMayfield wrote:Since neutrinos are nearly impossible to detect how can [the] origin (the direction they come from) of the very few that are detected be determined?

When neutrinos are associated with a transient or intermittent source, the signal rises above the background rate.

Yes, as when a spike in detection corresponds with a SN blast.
If you have two or more widely separated detectors, you can correlate those peaks (looking at arrival time) and determine a direction. In the case of steady sources which add to the background, you can statistically correlate all arrival times at one station with those from another and identify source directions.

I see. Thanks.

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The birth of a new field

Postby bystander » Tue Apr 18, 2017 4:02 pm

The birth of a new field
astrobites | 2017 Apr 14
Kelly Malone wrote:
Today’s paper is historical in nature rather than a current summary – it describes the 1989 paper that essentially birthed the field of ground-based gamma-ray astrophysics by making the first > 5 sigma detection of a TeV gamma-ray source! ...

Observation of TeV gamma rays from the Crab Nebula using the Atmospheric Cerenkov Imaging technique - T. C. Weekes et al
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Reionization of Dwarfs in the Local Group

Postby bystander » Tue Apr 18, 2017 4:09 pm

Reionization of Dwarfs in the Local Group
astrobites | 2017 Apr 17
Stacy Kim wrote:
There was a time in the universe when there were no stars. It was only after a long, dark 100 million years or so that the first stars—giant, blindingly bright monoliths a species apart from today’s stars—blinked on. As these stars blazed to life, they unleashed vast amounts of energetic ultraviolet (UV) photons. The universe at that time was filled mostly with cold hydrogen gas—cold enough to be in neutral form, single atoms of hydrogen. The UV photons unleashed by the stars changed this—they heated up the hydrogen gas and broke the atoms up into bare protons and electrons. This process was so efficient that the entire universe was reionized. ...

Reionization of the Milky Way, M31, and Their Satellites
I: Reionization History and Star Formation
- Keri L. Dixon et al
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Live fast, die young: quiescent galaxies in the early universe

Postby bystander » Tue Apr 18, 2017 4:20 pm

Live fast, die young: quiescent galaxies in the early universe
astrobites | 2017 Apr 18
Christopher Lovell wrote:
Galaxies in the early universe tend to be young and carefree. They have plenty of gas, and set about vigorously forming lots of stars. As a galaxy gets older though, it starts to run out of gas and becomes quiescent, no longer forming stars (see these bites for more details on quiescent galaxies). Theorists predict that it takes at least a few gigayears to deplete the gas, and this can be sped up by mergers and interactions with other galaxies. So, the further away we look (which corresponds to looking further back in time) the fewer quiescent galaxies we expect to see.

Today’s paper is about the snappily named ZF-COSMOS-20115, a quiescent galaxy at the unusually high redshift of 3.7, around one and a half billion years after the big bang. It has a mass equivalent to 170 billion suns, making it one of the most massive galaxies at this point in the universe’s history (much bigger than other similarly quiescent galaxies at this time), but it’s also very compact, less than a kiloparsec across (in comparison, our own Milky Way is ~ 50 kiloparsecs across). How did ZF-COSMOS-20115 become quiescent so quickly after forming, and is it a challenge to our current understanding of galaxy evolution? ...

A massive, quiescent galaxy at a redshift of 3.717 - Karl Glazebrook et al

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Active Cryovolcanism on Europa?

Postby bystander » Sat Apr 22, 2017 7:59 pm

Active Cryovolcanism on Europa?
astrobites | 2017 Apr 20
Joseph Schmitt wrote:
Europa, one of Jupiter’s Galilean moons, is one of the most exciting places in the search for alien life in our solar system, rivaling both Mars and Saturn’s moon Enceladus. Underneath a 15-25 km surface layer of ice, Europa very likely has a thick (~100 km) ocean of salty water with a rocky seafloor. Chemical reactions on the icy surface caused by high-energy particles from Jupiter’s radiation belts could provide some of the essential ingredients for life, but only if this material could somehow reach the liquid water beneath it. These geological properties make Europa a prime candidate for potential alien life. ...

The authors of the article in today’s Astrobite did follow-up Hubble observations in early 2016. They also observed a potential plume of water vapor in the same location as the previous observations, although they were still unable to definitively confirm it. There are two popularly supported mechanisms for creating these plumes: an explosion of dissolved gases in a pressurized liquid after the outside pressure has been removed and the expansion of ice when a trapped body of water freezes that then breaks out of its enclosure. ...

Active Cryovolcanism on Europa? - William B. Sparks et al
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Cradles of Massive Stars

Postby bystander » Sat Apr 22, 2017 8:16 pm

Cradles of Massive Stars
astrobites | 2017 Apr 20
Benny Tsang wrote:
Today let’s talk about massive stars! My favorite view of massive stars is the Hubble image of the star cluster R136 in the Large Magellanic Cloud. All the blue shining spots in this picture are massive stars, with masses up to hundreds of solar masses that are million times brighter than the sun! Massive stars bring beauty to our night skies, as well as structures to our Universe. The Hubble image shows massive stars in their magnificent adulthood. But have you ever wondered what they looked like when they were still babies? ...

Thermal Feedback in the High-mass Star and Cluster Forming Region W51 - Adam Ginsburg et al
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2 slow, 2 furious

Postby bystander » Sat Apr 22, 2017 8:39 pm

2 slow, 2 furious
astrobites | 2017 Apr 21
Paddy Alton wrote:
Scientific papers are a bit like buses. Sometimes you wait for ages waiting for one to take you where you want to go, then – surprise, surprise – two come along at once. This is, of course, a fundamental physical law, to which even astrophysicists are not immune.

In today’s article I’m going to break with tradition a little bit and highlight not one, but two papers, released weeks apart and with similar goals. This happens reasonably often, principally because if the science is both exciting and possible, chances are more than one team are looking into it! It’s always interesting to see independent groups take on the same question – and of course, the replicability of results is at the core of the scientific method. So for those reasons, and in the interests of fairness, let’s look at two takes on the origin of fast and slow rotating elliptical galaxies. ...

The MASSIVE Survey - VII. The Relationship of Angular Momentum,
Stellar Mass, and Environment of Early-Type Galaxies
- Melanie Veale et al
The SAMI Galaxy Survey: Mass as the Driver of the Kinematic
Morphology - Density Relation in Clusters
- Sarah Brough et al
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