About Me

I am a Senior Staff Scientist working on the Advanced Camera for Surveys (ACS) team within the Instruments Division at STScI. ACS is a third-generation Hubble Space Telescope instrument, and is one of the two operational imaging cameras on the spacecraft. I am also an active member of the Cosmicflows, PHANGS, and SH0ES collaborations.

I was a graduate student at the Institute for Astronomy at the University of Hawaii, where I obtained my PhD working with my advisor Brent Tully on nearby galaxies, the distance ladder, and large-scale structure.

I received my A.B. in Astronomy and Physics at Vassar College, where I worked with Fred Chromey on both observational and theoretical studies of contact binary systems. I also spent a summer working with Elizabeth McGrath at Colby College, where I studied the evolution of massive quiescent galaxies using CANDELS. I then attended Boston University, where I obtained my M.A. and studied optical, infrared, and x-ray emission from clusters of galaxies with Elizabeth Blanton.

Research Interests

I have a variety of research interests, including:

  • Star Formation in Nearby Galaxies
  • The Distance Ladder
  • The Hubble Constant
  • Large-Scale Structure


  • Most of my present research time is being spent on Cycle 1 and 2 JWST programs GO-1685 (PI A. Riess), 2875 (PI A. Riess), and 3055 (PI R. Tully).

    First results from GO-1685 and GO-2875 are available here: Riess+23, Riess+24, Li+24, Anand+24a, Li+24b, and Riess+24b.

    First results from GO-3055 are available here: Anand+24b and Anand+24c.

Recent Highlights

A few highlights from my recent work:

The TRGB–SBF Project. II. Resolving the Virgo Cluster with JWST (Anand+24c)

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 Validates HST Distance Measurements (Riess+24b)

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.

The TRGB–SBF Project. I. A TRGB Distance to the Fornax Cluster (Anand+24b)

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.

Tip of the Red Giant Branch Distances with JWST: An Absolute Calibration in NGC 4258 and First Applications to Type Ia Supernova Hosts (Anand+24)

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).

Peekaboo: The Extremely Metal Poor Dwarf Galaxy HIPASS J1131-31 (Karachentsev+23)

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.

Cosmicflows-4 (Tully+23)

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.

Publications

Publication Summary:

50 Refereed Publications (9 as first author)
4 Papers Under Review (1 as first author)
4 Instrument Science Reports (3 as first author)
3100+ Citations (400+ as first author), h-index = 21

NASA/ADS Link to All Publications