Gravity Grinch

Gravity Grinch

@gravitygrinch.bsky.social

observational cosmologist -- the particle horizon is the limit! https://thegravitygrinch.blogspot.com

629 followers179 following249 posts

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Gravity Grinch
@gravitygrinch.bsky.social

I am over the moon to be selected as the first astrophysicist to receive an O'Shaughnessy fellowship, being part of the 2026 cohort out of almost 12,000 applications! Thank you, Jim and the entire team of @osventuresllc.bsky.social for the support! www.prnewswire.com/news-release...

prnewswire.comO'Shaughnessy Ventures Backs Astrophysicist Challenging Assumptions About How Much Dark Matter the Universe Needs/PRNewswire/ -- O'Shaughnessy Ventures LLC (OSV), an investment firm that empowers creators, has awarded an O'Shaughnessy Fellowship to Jenny Wagner, an...
Gravity Grinch
@gravitygrinch.bsky.social

“Is that what happened?” asks Stacy McGaugh. “I’m not convinced that that’s the only way that can happen.” Without definitively knowing their origin story, McGaugh doesn’t think it’s possible to say anything about the nature of dark matter itself. That's the way we should approach this problem! 💯

Stacy McGaugh@dudedarkmatter.bsky.social

Story out in Quanta about the diffuse galaxies DF2, DF4, & DF9. It conveys the message that these objects are the nail in the coffin for MOND. Is it so? www.quantamagazine.org/triplet-of-g...

quantamagazine.orgTriplet of ‘Ghostly’ Galaxies Hints at What Dark Matter Is — and Isn’t | Quanta MagazineA collision may have left these galaxies without dark matter. That spells trouble for alternative gravity theories.

Gravity Grinch reposted

Tom Rice
@tomr-stargazer.bsky.social

AAS's Shapley Visiting Lectures Program is looking for prospective *lecturers* and *host sites* to join us! If you and/or your institution are enthusiastic about sharing astronomy with broad audiences, please consider applying. Learn more here: aas.org/posts/news/2... #astro #astroedu

aas.orgCall for Applications: 2027 Shapley Visiting Lectures ProgramThe AAS announces its call for applications for the Harlow Shapley Visiting Lectures Program. We are seeking astronomers and host institutions to participate in 2027!
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Gravity Grinch
@gravitygrinch.bsky.social

My plan is to broaden the audience with more English content and, of course, lobby for a fact-based scientific approach. I would like to tackle the problems we have with the tools that are suitable and not just run after trendy methods for the sake of their "coolness".

Gravity Grinch
@gravitygrinch.bsky.social

Happy to announce that my paper on galaxy infall models together with David Benisty is now published in Astronomy & Astrophysics, thanks a lot to the journal for the great processing! doi.org/10.1051/0004... #GalaxyKinematics #astronomy #astrophysics #AstrophysicsOfGalaxies

doi.orgGalaxy infall models for arbitrary velocity directions | Astronomy & Astrophysics (A&A)MendeleyAstronomy & Astrophysics (A&A) is an international journal which publishes papers on all aspects of astronomy and astrophysics
Gravity Grinch @gravitygrinch.bsky.social

Paper day again! Have a look at our findings on galaxy infall models, first time checked with simulations (up to our knowledge): arxiv.org/abs/2501.13149 Thread about the main results below. Endure the equations, stay for the final punch on clusters! 🧶 #astronomy #cosmology #GalaxyKinematics

arxiv.orgGalaxy infall models for arbitrary velocity directionsFor most galaxies in the cosmos, our knowledge of their motion is limited to line-of-sight velocities from redshift observations. To determine the radial velocity between two galaxies the minor and ma...

Gravity Grinch reposted

Gravity Grinch
@gravitygrinch.bsky.social

Here is my next YouTube short about the great discovery by David Benisty et al. that the cosmological constant can be inferred from the Milky Way and Andromeda system! This is so important because it's a complementary probe to the CMB. youtube.com/shorts/mwF0H... #astronomy #scicomm #YouTube

youtube.comKosmologische Konstante • Messbar in unserer Galaxiengruppe? | Jenny WagnerYouTube video by Urknall, Weltall und das Leben
Gravity Grinch
@gravitygrinch.bsky.social

I asked ChatGPT, Claude, Grok, and deepseek to flip a png that contained text and then flip the text to be readable again. Deepseek can't handle images, Claude did sth crazy & useless output, Grok similarly, Chat just flipped the image but not the text. Can this be done? How? #Chatgpt

Gravity Grinch reposted

Gravity Grinch
@gravitygrinch.bsky.social

Happy 91th birthday to #RoyKerr -- the man who made a #BlackHole spin and who assured me that his cat is safe from any thought experiments related to his research! 🥂 (Picture by his lovely wife taken from the bird platform...) #astronomy #astrophysics #cosmology

Gravity Grinch
@gravitygrinch.bsky.social

Happy 91th birthday to #RoyKerr -- the man who made a #BlackHole spin and who assured me that his cat is safe from any thought experiments related to his research! 🥂 (Picture by his lovely wife taken from the bird platform...) #astronomy #astrophysics #cosmology

Gravity Grinch
@gravitygrinch.bsky.social

...and if you want to know more about the motions of the galaxies around M81 and M82 and what we know about relative velocities between pairs, groups, and galaxy clusters, check out our new paper on relative kinematics: arxiv.org/abs/2501.13149 #astronomy #astrophysics #GalaxyKinematics

arxiv.orgGalaxy infall models for arbitrary velocity directionsFor most galaxies in the cosmos, our knowledge of their motion is limited to line-of-sight velocities from redshift observations. To determine the radial velocity between two galaxies the minor and ma...
Apodsky@nasapodsky.bsky.social

Astronomy Picture from 04/07/2013 M82: Starburst Galaxy with a Superwind Source: https://apod.nasa.gov/apod/ap130704.html #M82 #CigarGalaxy #StarburstGalaxy #Superwind #GalacticSuperwind #Astronomy #Astrophysics #Space #Galaxy #DeepSpace #Cosmology #Astrophotography #UrsaMajor

Gravity Grinch
@gravitygrinch.bsky.social

Black Hole Week might be over, but today's arxiv had an interesting paper on a dwarf galaxy where a black hole provided enough mass to explain the observables and a dark-matter halo fit seems disfavoured: arxiv.org/abs/2505.06198 #BlackHole #astronomy #astrophysics #DarkMatter

arxiv.orgThe "Dark-Matter Dominated" Galaxy Segue 1 Modeled with a Black Hole and no Dark HaloThe dwarf spheroidal galaxy, Segue 1, is thought to have one of the largest ratios of dark matter to stellar mass. Using orbit-based dynamical models, we model Segue 1, including a dark halo and a cen...

Gravity Grinch reposted

Gravity Grinch
@gravitygrinch.bsky.social

Question of the day: does someone know a (recent) catalogue of galaxy groups & clusters in our local universe with redshift-independent distances, redshifts and member galaxy properties like vel-disps? (we know Cosmicflows we are rather thinking of DESI or so) #astronomy #LocalUniverse #DarkMatter

Gravity Grinch
@gravitygrinch.bsky.social

Question of the day: does someone know a (recent) catalogue of galaxy groups & clusters in our local universe with redshift-independent distances, redshifts and member galaxy properties like vel-disps? (we know Cosmicflows we are rather thinking of DESI or so) #astronomy #LocalUniverse #DarkMatter

Gravity Grinch
@gravitygrinch.bsky.social

Very interesting stuff out there on the arxiv today! And still a Nick-Kaiser legacy paper!! Wow! arxiv.org/abs/2504.19922 #astronomy #cosmology #GalaxyClusters

arxiv.orgDynamical analysis of stacked samples of asymmetric, non-static, self-gravitating systemsWe use numerical simulations to explore biases that arise in dynamical estimates of the mean mass profile for a collection of galaxy clusters that have been stacked to make a composite. There are thre...
Gravity Grinch
@gravitygrinch.bsky.social

Fresh from the arxiv: arxiv.org/abs/2504.16991 check this interesting paper out which is a follow-up application to my previous paper with the first author. They now look at the impact of missing velocity components on the mass estimate of our Local Group. #astronomy #NearFieldCosmology

arxiv.orgLine-of-Sight Velocity Projection Impact on the Local Group MassThe mass of the Local Group (LG), comprising the Milky Way (MW), Andromeda (M31), and their satellites, is crucial for validating galaxy formation and cosmological models. Traditional virial mass esti...
Gravity Grinch
@gravitygrinch.bsky.social

Potentially new life found on other planets, but one special life lost on this planet this week: www.princeton.edu/news/2025/04... #JerryOstriker #Physicists #astrophysics #cosmology #DarkMatter

princeton.eduAstrophysicist Jeremiah P. Ostriker, pioneer of modern cosmology and ‘source of inspiration,’ dies at 87Ostriker is responsible for groundbreaking discoveries that forever changed the way astronomers think about what the universe is made of, including the existence of dark matter.
Gravity Grinch
@gravitygrinch.bsky.social

Fresh from the arxiv: calc. (numerically) the impact of a wave hitting a spherical overdensity in the cosmos, the wave suffers from a Shapiro delay and thus shows interference patterns. So do we really need fuzzy dark matter to observe interference?! arxiv.org/abs/2504.08286 #astronomy #DarkMatter

arxiv.orgNumerical evolution of Maxwell's equations for wavefronts propagating through a spherical gravitational potentialWe present a scheme for numerically solving Maxwell's equations in a weakly perturbed spacetime without introducing the usual geometric optics approximation. Using this scheme, we study light propagat...

Gravity Grinch reposted

Gravity Grinch
@gravitygrinch.bsky.social

Paper day again! Have a look at our findings on galaxy infall models, first time checked with simulations (up to our knowledge): arxiv.org/abs/2501.13149 Thread about the main results below. Endure the equations, stay for the final punch on clusters! 🧶 #astronomy #cosmology #GalaxyKinematics

arxiv.orgGalaxy infall models for arbitrary velocity directionsFor most galaxies in the cosmos, our knowledge of their motion is limited to line-of-sight velocities from redshift observations. To determine the radial velocity between two galaxies the minor and ma...