@franco_vazza@mastodon.social
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franco_vazza

@franco_vazza@mastodon.social

#SimulatedUniverses #AstroPhysicsFactlet
Astrophysicist at Bologna University and https://respublicae.eu/@ERC_Research grantee.
I study the cosmic web, extragalactic magnetism and clusters of galaxies with colorful simulations.

https://cosmosimfrazza.eu
#astrodon #astronomy

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franco_vazza, (edited ) to Astro
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#AstroPhysicsfactlet : we know that a cold front in the atmosphere brings freezing temperatures and lots of precipitation 🥶, but what about a cold front in a plasma of 10^8 K of temperature?
#Astrodon
#astronomy

franco_vazza, (edited )
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Similar to real cold fronts on our planet, colossal cold fronts also form when fluid perturbations displace dense and cold gas (having low entropy, where entropy is here commonly defined as S \propto T/n^2/3) and put it where hotter and less dense gas would normally be.

franco_vazza,
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..except that here hot means 1e8K and cold means 1e7K!
Plus the perturbation can be about a million light year wide, and it moves at several hundreds of kilometres per second.

franco_vazza, (edited )
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Several simulations have explored the formation of cold fronts at the centre of clusters of galaxies: they are predicted to form from the relatively gentle perturbation of small satellites crossing at some distance from the potential well of the mail cluster.
This results into a displacement of gas from the bottom of the gravitational potential well, which finds itself at a radius at which it is buyantly unstable.

franco_vazza, (edited )
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This phenomenon has been repeatedly observed by X ray telescopes, and most often using Chandra's exquisite spatial resolution

franco_vazza, (edited )
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A typical observational signature of cold fronts is that the densit and temperature profile across the front decrease in opposite directions, while the pressure is approximately constant. This allows to distinguish them from shocks, in which instead all quantities (including pressure) increase across the front, marking an irreversible heating process.

franco_vazza,
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For a fantastic tour of the real observation of one of the most famous cold front ( in the Perseus cluster) and on its numerical modelling: https://youtu.be/HeIgLnTFwNs
Enjoy!

franco_vazza, (edited )
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If you want instead to produce an analogic home simulation of the spiralling motions of a dense fluid after displacing it from its gravitational equilibrium, this is what M. Markevitch & A. Vikhlinin suggested to do (by posting exactly this picture) in 2007!
https://arxiv.org/pdf/astro-ph/0701821.pdf

franco_vazza,
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@notx I do confess

franco_vazza, to random
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Just spent the morning having an event with ~120 kids from the summer cap in my hometown (Vittorio Veneto, Prosecco province).

Intense!

Lot of magnets, balloon, we called a friend of mine in Australia to double check the reality of different time zones and seasons (✔️ )

#astrodon
#astronomy
#astronomia

franco_vazza,
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Kids were even asked question after the event, in a sort of post-match interview 😅

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franco_vazza,
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The new frontier/challenge was to have my own son as assistant, which he did very well.

I just had to stop him kicking my stage tools as a football

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franco_vazza, to ChatGPT
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Interesting read about the application of #chatgpt to numerical methods:

"ChatGPT for Programming Numerical Methods"
https://arxiv.org/pdf/2303.12093.pdf

#astronomy #astrodon

franco_vazza,
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(however: )

franco_vazza,
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@harcel I tried myself, with some useful results; but indeed in general in my experience you can only use it to "buy time" on problems you can resolve by yourself - otherwise impossible to trust results.

https://mastodon.social/@franco_vazza/110009702903329999

franco_vazza, to Astronomy
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Absolutely stunning rendering of real magnetic fields across a range of galaxies, observed with the SOFIA telescope for the Salsa survey:
https://arxiv.org/pdf/2303.13586.pdf on ApJ.

#WhatAboutMagneticFields
#astronomy
#astrodon

franco_vazza, to Astronomy
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Do you like Quentin Tarantino’s movies?

I honestly…don’t (much), but there are few catchy scenes.
In Kill Bill, the lead woman character uses the “5 point plan exploding heart technique” - a sequence of powerful pressure onto someone’s chest, after which the poor person can only walk 5 steps, and then dies.

Well…i am going to use this fuzzy scene to tell you about the limit to the the maximum propagation of ultra high energy cosmic rays, in this new #AstroPhysicsFactlet
#astronomy
#astrodon

franco_vazza, to space
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#paperday
#astrodon
#astronomy

Here is our attempt to study the formation of Mega Radio Halos with cosmological simulations - work led by Luca Beduzzi (master student at Uni PD)
https://arxiv.org/abs/2306.03764
Bottom line:
the formation of this new class of giant radio objects appear compatible with the continuous turbulent re-acceleration of fossil electrons, operating on Gyr timescales.

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franco_vazza, to space
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Astronomers have a relatively easier path for discovering things than other scientists:
the Universe is BIG and it shines in many different wavelengths, so any time there is a more powerful telescope, or a new region of the EM spectrum to explore, it’s a good chance to discover new objects and give new nicknames.

A new #AstroPhysicsFactlet dedicated to the nicknames that extragalactic astrophysicists gave to interesting clusters of galaxies they discovered

#astrodon
#astronomy

franco_vazza,
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  1. speaking of radio relics, my former PhD student Nicola Locatelli has discovered this weird one: the "Cornetto relic", which he named this way despite his supervisor advice not to start an holy war on twitter, with french colleagues claiming the superiority of Croissant ("cornetto"=is some italian version of the croissant).
    Of course, the twitter ware happened soon after that)
    https://twitter.com/maximetrebitsch/status/1253659108940578816

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franco_vazza,
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  1. not in the most politically correct way, at high redshift (z=0.87) we have "el Gordo" (=the fat one), or cluster SPT-CL J0102-4915, a very massive cluster formed when the universe was less than half its current size. It is a shrine to study lensing, magnetic field amplification and cluster dynamics.
    https://en.wikipedia.org/wiki/El_Gordo_%28galaxy_cluster%29

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franco_vazza,
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  1. the "Musket Ball Cluster", i.e. DLSCL J0916.2+2951, another merging cluster with a very clear separation between gaseous and total gravitational mass
    https://en.wikipedia.org/wiki/Musket_Ball_Cluster

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franco_vazza,
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  1. the "Spiderweb" (proto)cluster:

it is an irregular association of galaxies at the very high redshift of at z=2.15, which is believed to be the birth site of a cluster of galaxies, and which is keeping astronomers busy because it is a very cool environment to study how the mass of these systems is assembled, and possibly also how magnetic fields are released by the central galaxies as they evolve.

https://en.wikipedia.org/wiki/MRC_1138-262

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franco_vazza,
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  1. not really a cluster of galaxies, but close enough to belong to this category (and I am running out of names!): the Stephan's Quintet (https://en.wikipedia.org/wiki/Stephan%27s_Quintet) , which unlike its name suggest, actually is a physical association of 4 galaxies - the fifth is there only as an effect of perspective (and has instead a much different redshift - if you believe to the cosmological use of redshift to estimate distances - Alton Harp had a different view https://iopscience.iop.org/article/10.1086/303431/fulltext/33759.text.html)

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franco_vazza,
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  1. the Laniakea Supercluster: a supercondensation of galaxies in the local Universe, containing a about 1e17 solar masses (!) in total, and stretching for the impressive length of 160Mpc from side to side
    https://en.wikipedia.org/wiki/Laniakea_Supercluster
    Luckily you have one of the discoverers active on this platform: @pomarede

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franco_vazza,
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@acasalotti through telescope measurements one creates a 3d model of the distribution of mass at various distances from us, and then all the rest is a virtual reconstruction, which we can mock observe from every possible point of view!

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