Gravity Grinch

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".

Wagner, Jenny Dr. Jenny Wagner, Astrophysicist

At least something positive in these troublesome times: I am now a member of the advisory board for the Giordano Bruno Foundation in Germany:
www.giordano-bruno-stiftung.de/en/content/w...

#astronomy #humanism #scicomm

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

YouTube video by Urknall, Weltall und das Leben Kosmologische Konstante • Messbar in unserer Galaxiengruppe? | Jenny Wagner

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 video by Urknall, Weltall und das Leben Kosmologische Konstante • Messbar in unserer Galaxiengruppe? | Jenny Wagner

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

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

YouTube video by Urknall, Weltall und das Leben Licht, Gravitation & Einstein • Wie Masse Licht krümmt | Jenny Wagner

Good and bad news: my first #YouTube short was released today: youtube.com/shorts/410Fg...
good: I have more ideas what to do.
bad: the AI-translation really s****. Anybody got an idea how to improve that? Doing it in English from the start sounds the most reasonable for me....

#SciComm #Astronomy

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

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

...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

The "Dark-Matter Dominated" Galaxy Segue 1 Modeled with a Black Hole and no Dark Halo The 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...

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

Hope dies last that sth positive will emerge from the current crisis at universities... I have written the statement that outreach is more important than class-room-teaching so many times and it wasn't well received. Let's hope this attitude changes now!

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

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

That's wonderful! Interdisciplinary knowledge exchange is refreshing. I love such things! Happy to see you accepted the invitation, enjoy!

Dynamical analysis of stacked samples of asymmetric, non-static, self-gravitating systems We 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...

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

Line-of-Sight Velocity Projection Impact on the Local Group Mass The 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...

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

#AAS246 LAST CALL FOR LATE ABSTRACTS! To share your latest research with an eager audience of scientists at all career stages, submit your late abstract (for iPosters only) in one of more than 50 topical categories by 11:59 pm ET on Friday, 25 April. aas.org/meetings/aas...

Happy Earth Day to everyone and have a try writing your name or anything you like in earthly letters!
landsat.gsfc.nasa.gov/apps/YourNam...

Astrophysicist Jeremiah P. Ostriker, pioneer of modern cosmology and ‘source of inspiration,’ dies at 87 Ostriker 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.

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

Numerical evolution of Maxwell's equations for wavefronts propagating through a spherical gravitational potential We 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...

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

Wow! Welcome to my new followers! 🤩
Now that we are friends, I will think of a paper worth submitting (never tried).

Galaxy infall models for arbitrary velocity directions For 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...

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

6) This explains why mass estimates based on vel disps can be very accurate for high-z clusters based on the Delta v infall model!
For the rest, never underestimate unobserved velocity components, even at distances of 150 Mpc and validate your assumptions by simulations.

5) Yet, for each structure, the velocity dispersion of all infalling galaxies of the minor and major models yield lower (blue) and upper bounds (red) on the true vel disp. For small theta, the vel disp from Delta v is even a great estimate for the true one (grey on the black)!

4) For small theta, both models yield the difference of the line-of-sight vels ("Delta v"). But we can show that none of these models predicts the full radial velocity (black line), as the perpendicular components always have an impact! (x-axis: true v_rad, y-axis: infall models)

3) Major infall: projects the obs. line-of-sight vels onto the infalling galaxy's line of sight to determine the major infall velocity from these projections (see the green, light red and blue arrows). This is asymmetric and again only an approx. to the full rad. velocity.

2) Minor infall: takes the observed line-of-sight velocities and projects them onto the radial connection.
It thus misses to include velocity components perpendicular to our lines of sight. Yet, one thinks they have a small impact: the smaller theta, the smaller their impact.

1) Infall models describe the relative radial motion (red) between galaxies or between a galaxy infalling into a larger structure. How to calculate it when all we have is observations along our lines of sight (grey-blue)? That's the reason there are two infall models!

Galaxy infall models for arbitrary velocity directions For 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...

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