Dr. Deep Anand

We use JWST TRGB distances calibrated using the megamaser galaxy NGC 4258 to determine a new Cepheid-independent SBF zero point for HST. This new calibration, along with improved optical color measurements from PanSTARRS and DECam, gives an updated value of the Hubble constant = 73.8 +/- 0.7 +/- 2.3 km/s/Mpc that is virtually identical to the previously published result based on SBF distances calibrated using Cepheids. JWST observations of the Coma cluster will soon establish a foundation for the SBF calibration that will extend to much larger distances than is possible with HST.

The Virgo Cluster is the nearest substantial cluster of galaxies to the Milky Way and a cornerstone of the extragalactic distance scale. Here, we present JWST/NIRCam observations that simultaneously cover the cores and halos of ten galaxies in and around the Virgo Cluster and are designed to perform simultaneous measurements of the tip of the red giant branch (TRGB) and surface brightness fluctuations (SBF). The work presented here is part of a larger program to develop a Population II distance scale through the TRGB and SBF that is completely independent of the prominent Cepheid + Type Ia supernova ladder.

JWST provides new opportunities to cross-check the HST Cepheid/SNe Ia distance ladder, which yields the most precise local measure of the Hubble constant. Here we combine Cycle 1+2 JWST samples and find excellent agreement between the Cepheid, JAGB, and TRGB distance indicators, further strengthening the Hubble Tension.

Here we present JWST observations of three early-type Fornax Cluster galaxies, the first of fourteen observations from a Cycle 2 JWST program. Our modest integration times allow us to measure highly precise tip of the red giant branch (TRGB) distances, and will also be used to perform measurements of Surface Brightness Fluctuations (SBF). With eleven more scheduled observations in nearby elliptical galaxies, our program will allow us set the zero point of the SBF scale to better than 2% for more distant measurements, charting a path towards a high-precision measurement of the Hubble constant that is independent of the traditional Cepheid-SN Ia distance ladder.

With the advent of JWST, there is great promise to utilize the tip of the red giant branch (TRGB) to measure galaxy distances out to at least 50 Mpc, significantly further than HST's reach of 20 Mpc. Here we present the first calibration of the absolute magnitude of the TRGB in JWST/NIRCam filters. We also perform measurements of the TRGB in two Type Ia supernova hosts, and find good agreement between our TRGB distances and previous distances to these galaxies from Cepheids (Δ= 0.01 ± 0.06 mag), with the differences being too small to explain the Hubble tension (∼0.17 mag).

We present JWST NIRCam observations designed to test if a residual crowding bias in HST photometry is the cause of the Hubble Tension. We find excellent agreement between HST and JWST Cepheid distances, providing the strongest evidence yet that systematic errors in HST Cepheid photometry do not play a significant role in the present Hubble Tension.

Here we present HST imaging and SALT spectroscopy for HIPASS J1131-31, a galaxy found in such close proximity of a bright star that we call it Peekaboo. We find it to be one of the most extremely metal poor galaxies known. Most importantly, the red giant branch of the system is tenuous compared with the prominence of the features of young populations in the colour-magnitude diagram, inviting speculation that Peekaboo is a primordial galaxy in the local universe.

We present PHANGS-JWST, a JWST imaging survey of 19 spiral galaxies with the goal of providing an inventory of star formation, accurate measurement of the mass and age of star clusters, identification of the youngest embedded stellar populations, and characterization of the physical state of small dust grains in our target galaxies.

Cosmicflows is a program to compile galaxy distances and parse observed velocities into components due to the expansion of the universe and residuals due to gravitational interactions. Our fundamental interest is to derive inferences regarding the large-scale structure of the universe from galaxy test particle peculiar motions. Cosmicflows-4 is the largest compendium of galaxy distances on a uniform extragalactic distance scale, with 55,877 galaxies gathered into 38,065 groups.