Alex Ji
@alexji.bsky.social
Near-field Cosmologist and Assistant Professor of Astronomy and Astrophysics at University of Chicago. he/him
Apparently the kids don’t drink at conferences anymore so it’s up to Chiaki and me to hold down the fort
July 10, 2025 at 4:34 AM
Apparently the kids don’t drink at conferences anymore so it’s up to Chiaki and me to hold down the fort
Wei Jia Ong on nuclear astrophysics: “All nuclear data are good, but some nuclear data are better than others” -George Orwell, probably
July 9, 2025 at 8:45 PM
Wei Jia Ong on nuclear astrophysics: “All nuclear data are good, but some nuclear data are better than others” -George Orwell, probably
@astrokatie.com is telling us how the universe ends at UChicago tonight!
February 8, 2025 at 12:31 AM
@astrokatie.com is telling us how the universe ends at UChicago tonight!
This was last night!!
December 20, 2024 at 3:39 PM
This was last night!!
As a quick guess, I used ADS to query all ~1800 RNAAS papers and flagged which had arXiv. To estimate seniority I counted the number of papers for each first author (clearly wrong from common name overlap) and ran logistic regression. p=0.06 significance, might be stronger with a better metric.
November 28, 2024 at 7:04 PM
As a quick guess, I used ADS to query all ~1800 RNAAS papers and flagged which had arXiv. To estimate seniority I counted the number of papers for each first author (clearly wrong from common name overlap) and ran logistic regression. p=0.06 significance, might be stronger with a better metric.
November 11, 2024 at 1:46 PM
OK now I'm mad at LLMs
October 17, 2024 at 6:51 PM
OK now I'm mad at LLMs
#dwarfgalaxies2024 Will Bowman: Dragonfly Ultrawide Survey search for LSB galaxies. An amazing image here of cirrus. The data storage/reduction is done in the cloud on AWS (costs ~$100s/month, few $1000s for full reduction for 20k core hours or a few days wall time)
August 2, 2024 at 10:40 AM
#dwarfgalaxies2024 Will Bowman: Dragonfly Ultrawide Survey search for LSB galaxies. An amazing image here of cirrus. The data storage/reduction is done in the cloud on AWS (costs ~$100s/month, few $1000s for full reduction for 20k core hours or a few days wall time)
#dwarfgalaxies2024 Viraj Manwadkar adds chemical evolution to the GRUMPY dwarf galaxy formation model (including stochastic IMF and IGM sampling). Can broadly reproduce MW satellite population chemistry just based on the default model without any tuning.
August 2, 2024 at 9:33 AM
#dwarfgalaxies2024 Viraj Manwadkar adds chemical evolution to the GRUMPY dwarf galaxy formation model (including stochastic IMF and IGM sampling). Can broadly reproduce MW satellite population chemistry just based on the default model without any tuning.
#dwarfgalaxies2024 Zhu also ran hydrodynamical simulations showing that the CGM of dwarf galaxies is removed very quickly and leaves CGM tails (that form HI but not stars).
August 2, 2024 at 9:17 AM
#dwarfgalaxies2024 Zhu also ran hydrodynamical simulations showing that the CGM of dwarf galaxies is removed very quickly and leaves CGM tails (that form HI but not stars).
#dwarfgalaxies2024 Jingyao Zhu: new spatially resolved HI survey with WALLABY and MHONGOOSE. With DR1 see that some hosts have very high numbers of HI-rich satellites.
August 2, 2024 at 9:15 AM
#dwarfgalaxies2024 Jingyao Zhu: new spatially resolved HI survey with WALLABY and MHONGOOSE. With DR1 see that some hosts have very high numbers of HI-rich satellites.
#dwarfgalaxies2024 Li also found by chance an isolated quenched dwarf called Hedgehog. So far the isolated quenched dwarfs are unusually small.
August 2, 2024 at 9:01 AM
#dwarfgalaxies2024 Li also found by chance an isolated quenched dwarf called Hedgehog. So far the isolated quenched dwarfs are unusually small.
#dwarfgalaxies2024 Jiaxuan Li: ELVES-dwarf search for logMstar > 5.7 with surface brightness fluctuations out to 10Mpc from the ground around 41 isolated LMC-SMC hosts. So far consistent with SHMR from larger galaxies. Roman can do SBF of unresolved Rubin detections out to 50Mpc
August 2, 2024 at 9:01 AM
#dwarfgalaxies2024 Jiaxuan Li: ELVES-dwarf search for logMstar > 5.7 with surface brightness fluctuations out to 10Mpc from the ground around 41 isolated LMC-SMC hosts. So far consistent with SHMR from larger galaxies. Roman can do SBF of unresolved Rubin detections out to 50Mpc
#dwarfgalaxies2024 a new survey + instrument Via will go on sky at MMT and Magellan with high-resolution spectroscopy in 2027 to follow up streams and dwarf galaxies
August 2, 2024 at 8:34 AM
#dwarfgalaxies2024 a new survey + instrument Via will go on sky at MMT and Magellan with high-resolution spectroscopy in 2027 to follow up streams and dwarf galaxies
#dwarfgalaxies2024 Rubin is coming on sky soon. It will go out to 1000x more volume of resolved stars.
August 2, 2024 at 8:31 AM
#dwarfgalaxies2024 Rubin is coming on sky soon. It will go out to 1000x more volume of resolved stars.
#dwarfgalaxies2024 Risa Wechsler summarizes the current and imminent growth in sheer numbers of objects from astronomical surveys
August 2, 2024 at 8:06 AM
#dwarfgalaxies2024 Risa Wechsler summarizes the current and imminent growth in sheer numbers of objects from astronomical surveys
#dwarfgalaxies2024 Claire Riggs: why do dwarf gradients appear outside-in? Suggest stellar reshuffling through stellar feedback instead of in situ radius retention. Dwarf galaxies form stars inside-out, star formation feedback moves old stars, but at different rates for different feedback models.
August 1, 2024 at 3:26 PM
#dwarfgalaxies2024 Claire Riggs: why do dwarf gradients appear outside-in? Suggest stellar reshuffling through stellar feedback instead of in situ radius retention. Dwarf galaxies form stars inside-out, star formation feedback moves old stars, but at different rates for different feedback models.
#dwarfgalaxies2024 holy cow those are *proper motion dispersions* with the same error bars as the radial velocities. Can rule out a cored profile with 2 sigma confidence. Next is Scl, UMi, and JWST!
August 1, 2024 at 2:11 PM
#dwarfgalaxies2024 holy cow those are *proper motion dispersions* with the same error bars as the radial velocities. Can rule out a cored profile with 2 sigma confidence. Next is Scl, UMi, and JWST!
#dwarfgalaxies2024 Eduardo Vitral breaks mass-anisotropy degeneracy in Draco with 18-year HST proper motions. This is how much 18 years is......
August 1, 2024 at 2:06 PM
#dwarfgalaxies2024 Eduardo Vitral breaks mass-anisotropy degeneracy in Draco with 18-year HST proper motions. This is how much 18 years is......
#dwarfgalaxies2024 Daniel Vaz: binaries can artificially inflate dwarf UFDs. Using MUSE-faint repeated observations + simulated binaries, infer these binary fractions, higher for young stellar populations.
August 1, 2024 at 2:00 PM
#dwarfgalaxies2024 Daniel Vaz: binaries can artificially inflate dwarf UFDs. Using MUSE-faint repeated observations + simulated binaries, infer these binary fractions, higher for young stellar populations.
#dwarfgalaxies2024 in questions, it was asked whether galaxies form below the atomic cooling limit. The answer is yes arxiv.org/abs/1403.6123
August 1, 2024 at 1:29 PM
#dwarfgalaxies2024 in questions, it was asked whether galaxies form below the atomic cooling limit. The answer is yes arxiv.org/abs/1403.6123
#dwarfgalaxies2024 Even when the JWST photometric calibrations were off, it was possible to form large massive galaxies in LCDM, and also the luminosity fraction should flatten at M_UV > -14 arxiv.org/abs/2304.13755
August 1, 2024 at 1:26 PM
#dwarfgalaxies2024 Even when the JWST photometric calibrations were off, it was possible to form large massive galaxies in LCDM, and also the luminosity fraction should flatten at M_UV > -14 arxiv.org/abs/2304.13755
#dwarfgalaxies2024 The new Aeos simulations by Kaley Brauer track individual stars and see that we can separate the hierarchical assembly history of a galaxy with chemical abundances.
August 1, 2024 at 1:22 PM
#dwarfgalaxies2024 The new Aeos simulations by Kaley Brauer track individual stars and see that we can separate the hierarchical assembly history of a galaxy with chemical abundances.