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Jay Cross
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Astronomy Papers hat Caught Fred's Eye n Today's arXiv
 
"Eye-catching" Papers submitted to Astro-archives today (Friday)Topics selected include:

Lyman Alpha Emitters, A Doppler Puzzle, NANOgrav Nine Year Data, The Square kilometer Array, Supernova Ia in the Infrared

Lyman alpha Emitting Galaxies in the Nearby Universe http://arxiv.org/abs/1505.07483 (Invited review). The Lyman alpha line is emitted from a hydrogen atom when an electron decays from the first excited state to the ground state. It is an important tracer of matter in the universe; but it is often difficult to detect because the Lyman emission is as likely to be absorbed as it is to be emitted. Some do survive, and in galaxies with high levels of star formation, these lines are outstanding. This is a primer on Alpha emissions. It highlights the fact that the ratio Lyman alpha emitters to non-emitters is one of the fastest evolving trends in the observed universe - much faster than other tracers; which is highly curious.

*IN-SYNC III: The dynamical state of IC 348 - A super-virial velocity dispersion and a puzzling sign of convergence * http://arxiv.org/abs/1505.07504 This is odd. Normally when we are looking nearly edge on at a galaxy or global cluster, the nearer (less reddened) wing will be at the same, (or slightly blue-shifted) when compared with background sources of the same galaxy. But if the leading extent of the cluster is redshifted relative to the background stars, it implies some kind of rapid implosion. This is unique.

The NANOGrav Nine-year Data Set: Observations, Arrival Time Measurements, and Analysis of 37 Millisecond Pulsars http://arxiv.org/abs/1505.07540 If this paper were a billboard, it would be shouting: WATCH THIS SPACE. In the abstract they talk about "Time correlated red signals in ten of the pulsars". This is the type of signature one would expect imprinted on the pulsar emissions by gravitational waves. The data presented in this paper is extremely noisy, but if follow-up papers and/or observations correlate this reddening with expected gravitational wave signatures this could be the first directly-detected (but very fuzzy) gravitational wave signature.

The Cosmic Dawn and Epoch of Reionization with the Square Kilometre Array http://arxiv.org/abs/1505.07568 It is fun to read about the optimistic prognostications about what the next generation of radio, gravitational and infrared telescopes will tell us about the birth of the universe. It should be sobering to be reminded that these are the revelations Carl Sagan predicted (thirty years ago) would be unveiled by the current generation of scopes.

Type Ia Supernova Cosmology in the Near-Infrared http://arxiv.org/abs/1505.07707 This is my 'heartburn' paper of the day. The authors are able to correlate the IR spectrum of supernova events with visual Hubble diagrams if they apply the 'stretch factor' rules to the IR scaling data. The heartburn comes from a number of recent papers which seriously challenge the treatment of data sets with 'stretch factors' that assume the rise-time and the fall-time of supernova events is highly correlated. (It is not.)
Abstract: The Lya emission line of HI is intrinsically the brightest feature in the spectrum of astrophysical nebulae, making it a very attractive observational tool with which to survey galaxies. Moreover as a UV resonance line, Lya possesses several unique characteristics that make it useful ...
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Astronomy Papers That Caught My Eye In Today's arXiv

There are 48 papers today (Wednesday), not counting replacements. 

Topics: Extrasolar Kuiper Belt, Exoplanet Detection Methods, Spectral properties of 67P/C-G

Extrasolar Kuiper Belt http://arxiv.org/abs/1505.06734 There is a wide (48 AU) debris disk around HD 115600, which is a fifteen million year old star in the Sco-Cen OB Association. This paper is about a careful study of the spectrum of this blue-gray disk which possibly has water-ice as its main constituent.

Exoplanet Detection Methods http://arxiv.org/abs/1505.06869 How do/can we detect exoplanets now and in the near future? This is a summary of the various methods now in use and possible in the short term, including how they work and what they miss. If you've been paying close attention, there isn't much new here, but it is good to seem them all in one place.

Spectral Properties of 67P/C-G http://arxiv.org/abs/1505.06888 Rosetta is flying along in the escort phase of the mission, looking at comet 67P/Churyumov-Gerasimenko with its instruments. We don't see a lot of papers about this because the ESA gives authors about a year of exclusive access to the data. Ths paper is about the Spectrophotometric properties of the nucleus of the comet, and in particular the color variations (mostly dark red) of the surface, and speculation as to the surface materials, including possibly SO2 Ice. Another paper from this mission looks at possible origins of the comet: http://arxiv.org/abs/1505.07021
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Astronomy Papers That Caught My Eye In Today's arXiv

There are 67 papers today (Tuesday), not counting replacements. 

Topics: H1 to H2, Counter-Rotating Parts of NGC 5813, Improved Weak Lensing, SN1987A's Fading Ring

H1 to H2 http://arxiv.org/abs/1505.06200 Star formation in molecular clouds is a process that we have simple models for, but they are, through observation, becoming more detailed. One of the factors which has a bigger influence than I'd have guessed is the transition of atomic Hydrogen into molecular Hydrogen in the dense clouds. Molecular Hydrogen is harder to heat radiatively, and so collapses more easily. This paper is about detailed observations of five dense spherical clouds of molecular Hydrogen in the Perseus molecular cloud in an effort to increase our understanding of how and when the conversion from atomic to molecular gas occurs, and what phases it goes through.

Counter-Rotating Parts of NGC 5813 http://arxiv.org/abs/1505.06226 When two similar-sized galaxies merge they don't always do it in a way that maintains the rotating directions of both. If you have two parts of a giant galaxy rotating in opposite directions, there must be some very hot boundaries where collisions of gas & dust if not stars should be common. X-Ray and UV studies of the nearby giant galaxy NGC 5813 show that it is very likely in this condition. This paper gives details.

Improved Weak Lensing http://arxiv.org/abs/1505.06501 There are a few ways of directly observing where dark matter must be based on its gravitational influence, and Weak Lensing is perhaps the most widely usable. Weak Lensing essentially looks at the distortion of background elliptical galaxies by foreground massive clusters. This paper is about something the authors call Direct Shear Mapping, which requires higher resolution and details spectral information to look at the apparent kinematics of the background galaxies, including spirals and ellipticals, and produces much smaller error-bars in the measurement of the distribution of foreground mass. This is a job for ALMA, and later SKA, and similar instruments.

SN1987A's Fading Ring http://arxiv.org/abs/1505.06669 SN1987A is that Supernova in the Large Magellanic Cloud, the remnant of which is the iconic double ring of hot spots (Thanks Hubble!). That supernova explosion became visible almost 30 years ago, and you'd expect its appearance to change, and it is changing. That inner ring of hot spots will be gone by about 2025.
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Astronomy Papers That Caught My Eye In Today's arXiv

There are 47 papers today (Monday), not counting replacements. 

Topics: Beam Pattern with Drones, Pluto's Undiscovered Moons, Distance to Inspiralling NS-NS

Beam Patterns with Drones http://arxiv.org/abs/1505.05885 Ever see a diagram of the beam pattern and side-lobes of radio telescopes? They are calculated and measured based on a combination of theory and a few measurements... until now. These maps are highly dependent on frequency and other factors, and now they can be measured accurately and thoroughly using commercially available drones. This paper looks at doing this for a 5 meter telescope, but the method could easily be applied to any sized device.

Pluto's Undiscovered Moons http://arxiv.org/abs/1505.05933 Pluto has five things orbiting it that we know of so far. If you've been paying attention to the New Horizons probe, you are aware that in this approach phase, there is an active search for new satellites and potentially rings around this dwarf planet. This paper by Alan Stern & Simon Porter discusses dynamically stable places that additional orbiting object might be, and hence where the search should be concentrated.

Distance to Inspiralling NS-NS http://arxiv.org/abs/1505.06046 There are a few Gravitational Wave Detectors on the Earth, including VIRGO and Advanced-LIGO. There is a new one planned in Europe called the Einstein Telescope, which uses a new geometry which makes it possible to estimate both the direction and distance to any inspiralling neutron star pairs within some reasonable distance.
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NIIIICE Thank you for posting this.....brain food mmmmm
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Astronomy Papers That Caught Fred's Eye In Today's arXiv

These are the Friday papers.
 
"Eye -catching" Papers submitted to Astro-archives today.

Is cosmography a useful tool for testing cosmology? http://arxiv.org/abs/1505.05503 Cosmography is using 'normal' assumptions about the universe: It is both homogeneous and isotropic on the largest scales. The authors look at the number of free parameters involved in conceptualizing the universe, and conclude that many possible cosmologies cannot be ruled out.

On the universality of luminosity-metallicity and mass-metallicity relations for compact star-forming galaxies at redshifts 0 < z < 3 http://arxiv.org/abs/1505.05853 Thirty years ago, it was widely accepted that as we looked back in time we would see a gradual shift in the metallicity of galaxies as they increase in metal content as they age. More and more papers are reaching this diverging conclusion: Metallicity is dependent upon the stellar environment but only varies slighty (if at all) over cosmic time.
Abstract: Model-independent methods in cosmology have become an essential tool in order to deal with an increasing number of theoretical alternatives for explaining the late-time acceleration of the Universe. In principle, this provides a way of testing the Cosmological Concordance (or ...
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Your eye is first drawn to the very reflective ice fields in the crater near the top of the picture, but look at the odd texture of the surface below it. No big new craters, but lots of little similar sized holes in the ground, almost like frozen bubbles in boiled mud.
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"Like frozen bubbles in boiled mud" sometimes I think I spend my free time all wrong.

I have never put boiling mud in the freezer. 
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Astronomy Papers That Caught Fred's Eye In Today's arXiv

These are the Thursday papers.
 
 "Eye-catching" Papers submitted to Astro-archives today. Topics selected include: Radio Loud Quasars, Ultra-fast detectors, ICECUBE results. 

Radio Loud AGNs are Mergers http://arxiv.org/abs/1505.07419 Active galactic nuclei (quasars); come in two broad categories: Type I (radio quite) and type II (radio loud). What does a black hole merger sound like? Loud; if this theory is true. Other papers have traced radio-loudness to our viewing angle, so I don't think we have heard the final word on this topic.

*Aqueye+: a new ultrafast single photon counter for optical high time resolution astrophysics * http://arxiv.org/abs/1505.07339
It is easy to overlook how important the charge-coupled device is to modern astronomy. But they are slow, limiting optical astronomy to integration periods of about one second or longer. New technologies are developing that capture events in microseconds rather than seconds, and the next generation of these cascading devices will push observational windows into tens of pico-seconds.

Search for Dark Matter Annihilation in the Galactic Center with IceCube-79 http://arxiv.org/abs/1505.07259 The search for Dark Matter particles is like filling out a Bingo card, only backwards: Filling in the squares which have been eliminated. One of the dark matter theories suggests that WHIMP annihilation will produce neutrinos with the right 'color' for detection by the ICECUBE neutrino detecting array at the south pole. For now, this is just another filled in hole on a prize-less Bingo card.
Abstract: We measure the merger fraction of Type 2 radio-loud and radio-quiet active galactic nuclei at z>1 using new samples. The objects have HST images taken with WFC3 in the IR channel. These samples are compared to the 3CR sample of radio galaxies at z>1 and to a sample of non-active ...
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Astronomy Papers That Caught My Eye In Today's arXiv

There are 48 papers today (Wednesday), not counting replacements. 

Topics: Extrasolar Kuiper Belt, Exoplanet Detection Methods, Spectral properties of 67P/C-G

Extrasolar Kuiper Belt http://arxiv.org/abs/1505.06734 There is a wide (48 AU) debris disk around HD 115600, which is a fifteen million year old star in the Sco-Cen OB Association. This paper is about a careful study of the spectrum of this blue-gray disk which possibly has water-ice as its main constituent.

Exoplanet Detection Methods http://arxiv.org/abs/1505.06869 How do/can we detect exoplanets now and in the near future? This is a summary of the various methods now in use and possible in the short term, including how they work and what they miss. If you've been paying close attention, there isn't much new here, but it is good to seem them all in one place.

Spectral Properties of 67P/C-G http://arxiv.org/abs/1505.06888 Rosetta is flying along in the escort phase of the mission, looking at comet 67P/Churyumov-Gerasimenko with its instruments. We don't see a lot of papers about this because the ESA gives authors about a year of exclusive access to the data. Ths paper is about the Spectrophotometric properties of the nucleus of the comet, and in particular the color variations (mostly dark red) of the surface, and speculation as to the surface materials, including possibly SO2 Ice. Another paper from this mission looks at possible origins of the comet: http://arxiv.org/abs/1505.07021
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Jay Cross

Astronomy  - 
 
Astronomy Papers That Caught My Eye In Today's arXiv

There are 67 papers today (Tuesday), not counting replacements. 

Topics: H1 to H2, Counter-Rotating Parts of NGC 5813, Improved Weak Lensing, SN1987A's Fading Ring

H1 to H2 http://arxiv.org/abs/1505.06200 Star formation in molecular clouds is a process that we have simple models for, but they are, through observation, becoming more detailed. One of the factors which has a bigger influence than I'd have guessed is the transition of atomic Hydrogen into molecular Hydrogen in the dense clouds. Molecular Hydrogen is harder to heat radiatively, and so collapses more easily. This paper is about detailed observations of five dense spherical clouds of molecular Hydrogen in the Perseus molecular cloud in an effort to increase our understanding of how and when the conversion from atomic to molecular gas occurs, and what phases it goes through.

Counter-Rotating Parts of NGC 5813 http://arxiv.org/abs/1505.06226 When two similar-sized galaxies merge they don't always do it in a way that maintains the rotating directions of both. If you have two parts of a giant galaxy rotating in opposite directions, there must be some very hot boundaries where collisions of gas & dust if not stars should be common. X-Ray and UV studies of the nearby giant galaxy NGC 5813 show that it is very likely in this condition. This paper gives details.

Improved Weak Lensing http://arxiv.org/abs/1505.06501 There are a few ways of directly observing where dark matter must be based on its gravitational influence, and Weak Lensing is perhaps the most widely usable. Weak Lensing essentially looks at the distortion of background elliptical galaxies by foreground massive clusters. This paper is about something the authors call Direct Shear Mapping, which requires higher resolution and details spectral information to look at the apparent kinematics of the background galaxies, including spirals and ellipticals, and produces much smaller error-bars in the measurement of the distribution of foreground mass. This is a job for ALMA, and later SKA, and similar instruments.

SN1987A's Fading Ring http://arxiv.org/abs/1505.06669 SN1987A is that Supernova in the Large Magellanic Cloud, the remnant of which is the iconic double ring of hot spots (Thanks Hubble!). That supernova explosion became visible almost 30 years ago, and you'd expect its appearance to change, and it is changing. That inner ring of hot spots will be gone by about 2025.
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Astronomy Papers That Caught My Eye In Today's arXiv

There are 47 papers today (Monday), not counting replacements. 

Topics: Beam Pattern with Drones, Pluto's Undiscovered Moons, Distance to Inspiralling NS-NS

Beam Patterns with Drones http://arxiv.org/abs/1505.05885 Ever see a diagram of the beam pattern and side-lobes of radio telescopes? They are calculated and measured based on a combination of theory and a few measurements... until now. These maps are highly dependent on frequency and other factors, and now they can be measured accurately and thoroughly using commercially available drones. This paper looks at doing this for a 5 meter telescope, but the method could easily be applied to any sized device.

Pluto's Undiscovered Moons http://arxiv.org/abs/1505.05933 Pluto has five things orbiting it that we know of so far. If you've been paying attention to the New Horizons probe, you are aware that in this approach phase, there is an active search for new satellites and potentially rings around this dwarf planet. This paper by Alan Stern & Simon Porter discusses dynamically stable places that additional orbiting object might be, and hence where the search should be concentrated.

Distance to Inspiralling NS-NS http://arxiv.org/abs/1505.06046 There are a few Gravitational Wave Detectors on the Earth, including VIRGO and Advanced-LIGO. There is a new one planned in Europe called the Einstein Telescope, which uses a new geometry which makes it possible to estimate both the direction and distance to any inspiralling neutron star pairs within some reasonable distance.
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I'm quite fascinated by the new look upon Pluto and it's surroundings. So much going on at the far end of our fair system....
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These papers submitted to Astro-archives "caught my eye" today:

 Topics selected include: Double white dwarfs, sub-millimeter galaxies, MOND, Tidal synchronization, Lunar Neutrons, Supernova IA UV pulses.

A double white dwarf with a paradoxical origin? http://arxiv.org/abs/1505.05144 According to current theory, paired White Dwarfs Stars should have similar stellar aging history: They should be more-or-less identical twins. Finding a gross exception, as this pair appear to be, does not blow the theory completely out of water; but if we find many more pairs which exhibit a similar trend; we have a new, improved stellar aging problem.

The SCUBA-2 Cosmology Legacy Survey: ALMA resolves the bright-end of the sub-millimeter number counts Dusty sub-millimeter galaxies were first discovered by radio astronomers in the late 1990's. Follow-up surveys and studies are slowly filling-out our knowledge of what appear to be highly clustered dusty galaxies. The search is handicapped, because there is little information in the optical bandwidths, and it is difficult to correlate infrared with radio sources. Never-the-less at this time, the submm galaxies appear to be over-dense in galaxies that are close together - eluding to a dusty, compact history for our universe.

Tidal synchronization of close-in satellites and exoplanets. II. Spin dynamics and extension to Mercury and exoplanets host stars http://arxiv.org/abs/1505.05384 Tidal synchronization leads to obit/rotational patterns with small number ratios. The more viscous the bodies, the smaller the ratios.

The effect of craters on the lunar neutron flux http://arxiv.org/abs/1505.05403 The implications of this paper are intriguing, if not out-right dumbfounding. The simple conclusion is that craters 'focus' neutron beams. There is nothing wrong with craters action as 'cosmic ray lenses'; but when raw numbers are plugged into lensing equations, but the lensing power is too high...unless the roughness of the crater is acting as a Fresnel lens.

Testing modified Newtonian dynamics in the Milky Way http://arxiv.org/abs/1505.05181 Yesterday, Antoniseb pointed out that MOND dynamics are sometimes used as a straw-man foil to investigate the veracity of Dark Matter. These authors go far enough to suggest observations in our own galaxy will either prove or disallow MOND dynamics in the near future.

Strong Ultraviolet Pulse From a Newborn Type Ia Supernova The debate on the progenitors of supernova type Ia is a decades-old riddle: Are these single or double degenerate events? The observation of a UV pulse is consistent with a single degenerate mode; but I don't think this is a smoking gun.
Abstract: We present Hubble Space Telescope UV spectra of the 4.6 h period double white dwarf SDSS J125733.63+542850.5. Combined with Sloan Digital Sky Survey optical data, these reveal that the massive white dwarf (secondary) has an effective temperature T2 = 13030 +/- 70 +/- 150 K and a ...
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Astronomy Papers That Caught My Eye In Today's arXiv

There are 47 papers today (Wednesday), not counting replacements. 

Topics: New MoND Limit, Tarantula Details, Another Dim Satellite, SN1a Stats

New MoND Limit http://arxiv.org/abs/1505.04790 Modified Newtonian Dynamics (MoND) is one of those theories that is mostly a straw man for Dark Matter to be compared with. You've probably heard of it, it has been around a long time. To that end it serves an important role. The idea of MoND is that Gravity has a small component that drops off more slowly than inverse-square, resulting in what looks like galactic and cluster halos, and explaining the rotational velocities of larger galaxies. Dark Matter supporters like to find ways to test MoND, and show that it cannot explain certain phenomena. This paper looks statistically at the vertical motion of stars in the solar neighborhood with the promise that Gaia data, once available, will be good enough to strongly constrain MoND's scope in explaining the effects of Dark Matter.

Tarantula Details http://arxiv.org/abs/1505.04799 30 Doradus (The Tarantula Nebula) is a massive star-forming region in the Large Magellanic Cloud. It has been the topic of some recent discussions I've been having, so this caught my eye. This paper is from the Hubble Treasury Project. The paper looks especially at the central densest part of this object called NGC 2070, and looks at the unexpectedly complex star formation history of this area. There's one nice images and a lot of entertaining graphs.

Another Dim Satellite http://arxiv.org/abs/1505.04948 The Milky Way has a lot of ultra-faint dwarf satellite galaxies, and the number we know of is slowly getting close to the number predicted by modelling software experiments. Horologium II is yet another one. It is about 250,000 light years away from here.

SN1a Stats http://arxiv.org/abs/1505.05086 This is yet another (important) paper on how to discern subtypes of Type 1a Supernovae, so as to be able to reliably, and with relative ease, use them for much more precise cosmological study.
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