Recently AGILE and Fermi have found short (4 and 16 day) and bright gamma-ray flares from the Crab Nebula. The short duration of these flares suggests that they were emitted via synchrotron radiation from 10^15 eV electrons in a very small region of the nebula <0.014 pc across. These characteristics pose serious challenges for particle acceleration theory.

Magnetic reconnection is a fundamental process in plasmas for converting magnetic to kinetic energy and is observationally seen in the solar corona, the solar wind, planetary magnetospheres, and laboratory thermonuclear fusion devices. It is a process that is commonly studied in the context of solar system plasmas, from reconnection in the solar corona, to its importance in space weather at Earth, to dynamics in the magnetospheres of the outer planets. These studies use observations, both in situ and using remote sensing, simulations using MHD, Hybrid, test particle, and PIC simulations.

In this paper the authors use relativistic test particle simulations and a magnetic reconnection model to explain the characteristics of gamma-ray flares in the Crab Nebula. The mathematical developemnt has much in common with fundamental studies of magnetic reconnection in solar system plasmas but with important differences. They find that the emission is highly collimated and that the synchrotron spectrum peaks above 100 MeV. The mechanism is a plausible explanation for the flares in nebula and may be important at other astrophysical objects.

The paper is fairly weighty and mathematical in places, but the majority of the paper is quite accessible and has some nice clear explanations of the basic physical effects at work in the acceleration of the particles.

Read the preview of the meeting here, and there’s also a full transcript of tweets too.

The discussion started with a simple question – do you tweet about your own papers?


when they go on arXiv, yes. – @augustmuench 



No, I never have but had never really considered doing so – @wikimir



I tweet about my papers, but then @galaxyzoo papers generally have a wider interested audience than others..? – @KarenLMasters 



I haven’t but I think I may in the future! – @evanocathain 



I find Twitter good for seeing papers from other fields that I might have missed, via summaries from @Awesome_Ph for example – @astronomyjc 


I have not yet tweeted about my own papers, but I probably would. I also tweet about friends’ papers. – @ Awesome_Ph 


…I tend to tweet about my papers, with no discernible impact. – @mike_peel 


Perhaps tweeting about papers suggests them as good for journal club discussion which would reach wider audience and so on? – @KarenLMasters



Could tweeting lead to more citations?

The paper finds a correlation between twitter mentions, downloads and citations I can see the link between tweets & downloads but I’m not sure that’d necessarily translate into citations in many astro fields – @astronomyjc 



Tweeting is a great way to reach a lot of people, but not necessarily reaching people in your direct field of research – @astronomyjc 



yeah, but any extra exposure could turn into citations. You never know – and there’s lots of papers these days… – @KarenLMasters 


but that’s good! i want new people to read my work – not people who would read it anyway. – @evanocathain 


I think (not just social) media coverage in principle gives a fair view of the ‘sexyness’ of research, not necessarily of quality.. – @ Awesome_Ph 


I think I’d never considered twitter for discussing the details of a particular paper (apart from ) – more suited to broader disc. – @wikimir 


I think that’s often how I use it – recommending blogs, links, stories -why not papers too? – @KarenLMasters 


Other options for keeping up with recent papers

I check the arXiv every morning so I generally see new papers in my field there, not on twitter – @astronomyjc


did you know there is a twitter service for the arxiv? – @KarenLMasters 


Just found @orbitingfrog made a “Arxiv on Twitter” webpage: http://t.co/v3hpyBdR – @KarenLMasters 


More from @orbitingfrog on his tweprint service: http://t.co/pqOwtv07 – @KarenLMasters 


Found @arxivblog which tweets physics papers. – @KarenLMasters 


I have an experiment ongoing looking for links to ads papers on Twitter – @doug_burke

That twitter arxiv automatic tweet service I mentioned is @AstroPHYPapers – @KarenLMasters

How many of you actually read papers because of twitter? – @Awesome_Ph

I read the paper this whole discussion is based on because of twitter – @astronomyjc 


I will sometimes read via twitter. I also check the arxiv separately. – @KarenLMasters

Have any of you cited a paper after seeing it on twitter? i.e. One that you wouldn’t otherwise have cited?

No, but it’s never been suitable. Not enough tweeters in my area that I’m aware of. – @wikimir

what @wikimir said re citing. too small of an echo chamber. still there are lots of things I “cite” because of twitter — ow mass star formation papers not so much… – @augustmuench

Only at the moment. In 5 yrs who knows? RT @augustmuench @_atjc what @wikimir said re citing. too small of an echo chamber. – @StephenSerjeant

Tweeting from the arXiv?

need to get arxiv to put a twitter button in their collection on bottom right – has Facebook and Linkedin already… – @KarenLMasters

And a “like” button. But I also want a “why did you bother doing this?” button – @StephenSerjeant

perhaps if not mentioned/cited you do get the message! – @KarenLMasters

How about http://t.co/lgAMhhbJ? RT @astronomyjc I’m not sure there’s a symbol to represent ‘why did you bother?’ – @StephenSerjeant

And finally…

Apparently, the way to get more traffic for your paper is to name it something awesome like “MCMC Hammer” – @dalcantonJD

You can also download the PDF: Tweet transcript archive.

Here’s the abstract:

We analyze the online response of the scientific community to the preprint publication of scholarly articles. We employ a cohort of 4,606 scientific articles submitted to the preprint database arXiv.org between October 2010 and April 2011. We study three forms of reactions to these preprints: how they are downloaded on the arXiv.org site, how they are mentioned on the social media site Twitter, and how they are cited in the scholarly record. We perform two analyses. First, we analyze the delay and time span of article downloads and Twitter mentions following submission, to understand the temporal configuration of these reactions and whether significant differences exist between them. Second, we run correlation tests to investigate the relationship between Twitter mentions and both article downloads and article citations. We find that Twitter mentions follow rapidly after article submission and that they are correlated with later article downloads and later article citations, indicating that social media may be an important factor in determining the scientific impact of an article.

I’ve highlighted some of the key points from the meeting in the review below. I couldn’t include everything though, so if you’re interested in the topic read the full tweet transcript.

Job advice – dos

Let’s start with a pretty broad question: what skills do you think are essential in getting an astro job? – @astronomyjc

some rambling tips on how to maximise chances of a fulfilling astro career coming right up

be lucky; be prepared to be mobile; publish high-quality work as 1st author; make sure your work gets seen – give good talk, often!

learn to write great proposals; avoid working in backwater subjects; understand priority management and behave accordingly

deliver on your promises – do not, under any circumstances, overcommit; try to avoid the 2-body problem

learn to be supremely efficient – exploit the great tools out there (evernote!); learn a rare skill (in UK, try interferometry)

do your bit, but don’t get sucked entirely into the outreach business – we can’t all be @profbriancox

remember than there is life outside HEI sector: UK national labs (UKATC!), ESO, ESA, NRAO, CSIRO – all superb employers

spend less time worrying about future job market and more time writing difficult few paras that finishes great paper – just do it!

- @robivison

I’ve been told that showing evidence of being able to attract independent funding is important – @kevinschawinski

Give talks at NAM, AAS, in ur dept, at confs. That is true thru ur career. I get frustrated at lack of travel money 4 that reason – @Matt_Burleigh

I don’t know if this is helpful, but tt faculty searches are often looking for people who will be leaders in their subarea.- @johngizis

lesson: look for new opportunities (instruments, fields). Fellowships often follow exploitation of new missions and instruments – @Matt_Burleigh

Number one thing at all levels is some sign of initiative – @e_astronomer

along the being prepared line, I think reading as many papers as possible is very helpful, both in getting ideas and in interviews.- @johngizis

Forget “prestigious institutes”. That means living on past glories. Make your own prestige. – @telescoper

Shocked to notice how little all this good advice resembles my early career path… must have been a different era – @NGC3314

But have to add the importance of “fit”. Candidates are culled because interests don’t “match”. So, good to develop “portfolio diversification”. Increases chance of “fit”, and demonstrates that you’re unlikely to ossify. – @dalcantonJD

Your CV is a brochure advertising you. Versality is good, as long as you don’t spread yourself too thin. – @telescoper

I think it is difficult to “package” what one should do at an early career in the path to whatever the ultimate goal. A career should be tailor made to ones own ultimate goal and it certainly is not a straight line for most of us! – @vrib_ast

and don’ts

don’t upset too many people. I dont mean keep quiet, but dont come across as arrogant, a bullshitter, a bore. dont behave badly – nicking other ppl’s data, cutting ppl off author lists, deliberately downgrading a rival’s proposal – @Matt_Burleigh

I can think of many people who love the sound of their own voice and it seems to push them on. Frustrating! – @samb8s

Some interview killers: undercut competitors, freeze in front of students, show contempt for institution/colleagues, display ego++ – @NGC3314

Dating other astronomers – the 2-body problem

@robivison what does try to avoid the 2-body problem mean?! sounds like don’t have a life … – @evanocathain

@robivison 2body problem is huge for many. It’s a real issue throughout academia. Unsolvable I think – @Matt_Burleigh

@Matt_Burleigh @robivison not just a problem for academia. It a problem for any mobile career. – @KarenLMasters

@Matt_Burleigh solvable, but unpleasant. prevent grief down the road – date outside your field, or date future nobel winner – @robivison

The hiring process

Our hiring: identifiable contribution in collaboration, coding>>using codes, capable of independent work, attract $$ (tenure must) – @NGC3314

Quantity over quality?

I often fear it is indeed quantity over quality. Many get involved in big projects to “bump up” their count – @Matt_Burleigh

times have changed. quality wins out over quantity every time for jobs in good depts. must still meet basic quantity criteria tho – @robivison

when you are a PDRA, you have the most chance to publish in ur career. Once you start teaching, time for own work disappears…. – @Matt_Burleigh

The importance of good references

I think reference letters matter as much as talks or papers. what do you think? – @therem

Strong normalization (i.e. unwritten code!) issues with ref letters, most weighted for v. junior people – @NGC3314

sadly, having a reference from a Big Name & having spent time at Distinguished Old Uni also helps – @Matt_Burleigh

definitely pays to find a couple of Big Names outside your institute (international = best) willing to write you a good reference – @robivison

agree with Rob re getting international profs in ur field to write letters for u. Helped me a lot. Buy them a beer…. – @Matt_Burleigh

I’m only realising now what a leg up a high profile supervisor is – even if they’re a crap supervisor – @sarahkendrew

referees who write skilfully help a lot : they may sell you better than you do – @e_astronomer

Luck

How big a factor does luck play? i.e. being in the right place at the right time, for instance when a new instrument comes online – @astronomyjc

can’t discount the luck factor, but there is absolutely no doubt that folk make their own – @robivison

luck is *extremely* important, so one has to maximize the number of acceptable possibilities – @therem

“the more I practice the luckier I get” – Gary Player. But I *hate* the 24/7/365 culture in academia and dont want to encourage it – @Matt_Burleigh

Being noticed

also, being noticed >> being right (last tweet: within limits, obvs…..) – @sarahkendrew

following the herd won’t make you stand out; but wacky stuff could make you look flaky. Tricky.- @e_astronomer

its true that the American “show & tell” culture is a great help to them. But if u push it too far…. – @Matt_Burleigh

lets settle on noticed and MIGHT be right – @e_astronomer

Paper authorship & team membership

Important generic point, though. If your supervisor doesn’t let you be first author, you’re doomed. – @telescoper

Indeed. I dont ever want to do that to my PhDs. So I hope no one holds the 2nd authorships against me… – @Matt_Burleigh

But much easier to get a Nature/Science paper under your belt if you’re an observationalist? – @dr_paul_woods

Nature/ Science papers not worth the candle. Usually trite. Doesn’t matter where it’s published if it’s good. – @telescoper

@dr_paul_woods @BuChanda “Stayed away from big projects, so I have few papers”. Why does that follow, logically? – @telescoper

‘Cos in big projects, other people write publications to which you contribute. When I first author, I do work – @dr_paul_woods

Re: freeloaders on many-author papers: Sometimes PDRAs have done shedloads of work so should get name on paper – @astrofairy

And finally…

People seem to be looking for universal rules, which is impossible as the process is fundamentally chaotic. Most important point was made by @robivison which is to be lucky. – @telescoper

but fortune favours the prepared mind. – @e_astronomer

You can also download the PDF: Tweet transcript archive.

Recently on twitter there have been plenty of discussions about what skills scientists are supposed to have in order to land a job. I guess such discussions pop up every year around job season. At the AAS meeting in Austin there was a special session about this too. The advice you often hear is: it’s not just your publication list, you need ‘the full package’ and expand your skill set beyond writing scientific papers. This sounds like perfectly reasonable advice. Still, when you are applying for jobs, more often than not the first cuts in the applicant pool are based on the number of first-author refereed papers. The quality of the papers seems less relevant for the selection process than some people think it should be.

Let’s discuss what skills are important for a scientist, both in terms of what a good scientist should do, and in terms of how this (should) translate into applicant selection process. What is the right way to go if you are, or soon will be, on the job market?

The original paper can be found here, our preview is here, and the full transcript of the meeting is here.

The meeting was kindly hosted (at short notice, after a minor panic on my part) by Simon from @RHULPhysics. Onto the review…

Simulations

We don’t see enough satellite gals compared to sims. How significant is this paper? Anyone see any problems with it? – @RHULPhysics

doesn’t that mean that simulations are wrong? why is that wrong? Explain … #devils_advocate – @evanocathain

Yup, I would have always started by assuming sims weren’t right yet, which is why observing more sats is so cool, no? – @RHULPhysics

Gravitational lens model

Interesting paper. I wonder how model dependent it all is… – @KarenLMasters

Do you mean model-dependent in their lensing detection? – @RHULPhysics

yes. Detection is from fitting mass model to the Einstein ring, I don’t understand how much degeneracy in that. – @KarenLMasters

And finally

IIRC there’s quite a few lenses with anomalous image flux ratios suggestive of substructure. – @StephenSerjeant

If other lenses suggest substructure, is this a better detection, or just a braver claim? – @RHULPhysics

Better detection I’d say – @StephenSerjeant

Glad to hear it. Fingers crossed for more! – @RHULPhysics

You can also download the PDF: Tweet transcript archive.

This new dwarf isn’t associated with our own Milky Way, but is the satellite of a more distant galaxy (z=0.881). It also appears to be composed primarily of dark matter, making it too faint to be detected with optical telescopes. It was found by gravitational lensing.

One of the current puzzles in astronomy is why galaxy simulations predict that a galaxy like the Milky Way should have thousands of dwarf satellites, when in fact only around thirty have been seen. Maybe this new, distant, dwarf galaxy holds the answer – what if they don’t have enough stars in them for us to see them?

There’s more details on this paper over at astrobites. It’s also been widely reported in the press. Here’s the abstract as well:

Abstract
The mass-function of dwarf satellite galaxies that are observed around Local Group galaxies substantially differs from simulations based on cold dark matter: the simulations predict many more dwarf galaxies than are seen. The Local Group, however, may be anomalous in this regard. A massive dark satellite in an early-type lens galaxy at z = 0.222 was recently found using a new method based on gravitational lensing, suggesting that the mass fraction contained in substructure could be higher than is predicted from simulations. The lack of very low mass detections, however, prohibited any constraint on their mass function. Here we report the presence of a 1.9 +/- 0.1 x 10^8 M_sun dark satellite in the Einstein-ring system JVAS B1938+666 at z = 0.881, where M_sun denotes solar mass. This satellite galaxy has a mass similar to the Sagittarius galaxy, which is a satellite of the Milky Way. We determine the logarithmic slope of the mass function for substructure beyond the local Universe to be alpha = 1.1^+0.6_-0.4, with an average mass-fraction of f = 3.3^+3.6_-1.8 %, by combining data on both of these recently discovered galaxies. Our results are consistent with the predictions from cold dark matter simulations at the 95 per cent confidence level, and therefore agree with the view that galaxies formed hierarchically in a Universe composed of cold dark matter.

Finally, don’t forget to join in the discussion on twitter on Thursday.