Resolved Stellar Populations

Unravelling the Star Formation History of the Universe

content_images/NGC253-080923_sm_thm

NGC253, a spiral galaxy 3.9 Mpc (13 million lightyears) from us.
From the ACS Nearby Galaxy Survey Treasury.


What can we learn from resolved stellar population studies?

Resolving the light of a galaxy into its constituent stars allows the structure and formation history of the galaxy to be studied in great detail. Color-magnitude diagrams of resolved stellar populations encode information about the buildup of stellar mass and metallicity over time; the star formation history within a galaxy can be derived by comparing photometric observations of stellar populations with stellar evolution models. Spatially resolved star counts allow galaxy features to be traced to much lower surface brightnesses than is possible with traditional surface photometry, enabling us to study the structure and properties (e.g., age and chemical enrichment) of faint thick disks and stellar halos. Stellar populations can be analyzed as a function of position within a galaxy, yielding a picture of the growth of the galaxy's subcomponents (for example, its disk or spheroid) over time. The Hubble Space Telescope can resolve individual stars and parsec-scale structures out to several megaparsecs, allowing us to study stellar populations, star formation histories, and stellar clusters in galaxies throughout the Local Volume.

ANGST and ANGRRR: Studying the Local Volume

The ACS Nearby Galaxy Survey Treasury (ANGST) (GO 10915, Dalcanton et al. 2009) was conceived as a systematic volume-limited imaging survey of every galaxy in the local universe outside the zero-velocity surface of the Local Group. All galaxies with distances of approximately 1 to 3.5 Mpc are included in the ANGST sample as long as they lie above the Galactic plane (|b|>20°). ANGST also includes an extension to 4 Mpc in the direction of the M81 group. The volume includes 69 galaxies spanning a large range of environment (filaments, small & large groups, close pairs, and isolated galaxies) and morphological type; the ANGST galaxies also span a factor of ~104 in luminosity and star formation rate. The first data release includes drizzled reference images and calibrated photometric catalogs comprising ~34 million measurements of ~14 million stars. The data can be found on the MAST website. The data can also be reached via the ANGST project website, which includes more information about the survey and data reduction as well as color-magnitude diagrams for all observations.

ANGRRR (PI: Dalcanton, PID 10945) will produce systematic and consistent reductions of archival ACS/WFC and WFPC2 observations of non-Local Group galaxies within 5 Mpc. The first ANGRRR data release is now available at MAST. It includes photometric catalogs for non-Local Group galaxies within 3.5 Mpc. Unlike ANGST, the ANGRRR galaxy sample has no restriction on galactic latitude.

Related Publications


''The Panchromatic Hubble Andromeda Treasury X. Ultraviolet to Infrared Photometry of 117 Million Equidistant Stars'' Williams, Benjamin F., Lang, Dustin, Dalcanton, Julianne J., Dolphin, Andrew E., Weisz, Daniel R., Bell, Eric F., Bianchi, Luciana, Byler, Eleanor, Gilbert, Karoline M., Girardi, Leo, Gordon, Karl, Gregersen, Dylan, Johnson, L. C., Kalirai, Jason, Lauer, Tod R., Monachesi, Antonela, Rosenfield, Philip, Seth, Anil, and Skillman, Evan, 2014, arXiv, arXiv:1409.0899.

''Constraints for the Progenitor Masses of 17 Historic Core-collapse Supernovae'' Williams, Benjamin F., Peterson, Skyler, Murphy, Jeremiah, Gilbert, Karoline, Dalcanton, Julianne J., Dolphin, Andrew E., and Jennings, Zachary G., 2014, ApJ, 791, 105.

''The Star Formation Histories of Local Group Dwarf Galaxies II. Searching For Signatures of Reionization'' Weisz, Daniel R., Dolphin, Andrew E., Skillman, Evan D., Holtzman, Jon, Gilbert, Karoline M., Dalcanton, Julianne J., and Williams, Benjamin F., 2014, ApJ, 789, 148.

''The Star Formation Histories of Local Group Dwarf Galaxies I. Hubble Space Telescope / Wide Field Planetary Camera 2 Observations'' Weisz, Daniel R., Dolphin, Andrew E., Skillman, Evan D., Holtzman, Jon, Gilbert, Karoline M., Dalcanton, Julianne J., and Williams, Benjamin F., 2014, ApJ, 789, 147.

''Supernova Remnant Progenitor Masses in M31'' Jennings, Zachary G., Williams, Benjamin F., Murphy, Jeremiah W., Dalcanton, Julianne J., Gilbert, Karoline M., Dolphin, Andrew E., Fouesneau, Morgan, and Weisz, Daniel R., 2012, ApJ, 761, 26.

''The Panchromatic Hubble Andromeda Treasury II. Tracing the Inner M31 Halo with Blue Horizontal Branch Stars'' Williams, Benjamin F., Dalcanton, Julianne J., Bell, Eric F., Gilbert, Karoline M., Guhathakurta, Puragra, Lauer, Tod R., Seth, Anil C., Kalirai, Jason S., Rosenfield, Philip, and Girardi, Leo, 2012, ApJ, 759, 46.

''The Panchromatic Hubble Andromeda Treasury I: Bright UV Stars in the Bulge of M31'' Rosenfield, Philip, Johnson, L. Clifton, Girardi, Léo, Dalcanton, Julianne J., Bressan, Alessandro, Lang, Dustin, Williams, Benjamin F., Guhathakurta, Puragra, Howley, Kirsten M., Lauer, Tod R., Bell, Eric F., Bianchi, Luciana, Caldwell, Nelson, Dolphin, Andrew, Dorman, Claire E., Gilbert, Karoline M., Kalirai, Jason, Larsen, Søren S., Olsen, Knut A. G., Rix, Hans-Walter, Seth, Anil C., Skillman, Evan D., and Weisz, Daniel R., 2012, ApJ, 755, 131.

"The Panchromatic Hubble Andromeda Treasury'' Dalcanton, Julianne J., Williams, Benjamin F., Lang, Dustin, Lauer, Tod R., Kalirai, Jason S., Seth, Anil C., Dolphin, Andrew, Rosenfield, Philip, Weisz, Daniel R., Bell, Eric F., Bianchi, Luciana C., Boyer, Martha L., Caldwell, Nelson, Dong, Hui, Dorman, Claire E., Gilbert, Karoline M., Girardi, Léo, Gogarten, Stephanie M., Gordon, Karl D., Guhathakurta, Puragra, Hodge, Paul W., Holtzman, Jon A., Johnson, L. Clifton, Larsen, Søren S., Lewis, Alexia, Melbourne, Jason L., Olsen, Knut A. G., Rix, Hans-Walter, Rosema, Keith, Saha, Abhijit, Sarajedini, Ata, Skillman, Evan D., and Stanek, Krzysztof Z., 2012, ApJS, 200, 18.

"The Star Formation History of Leo T from Hubble Space Telescope Imaging" Daniel R. Weisz, Daniel B. Zucker, Andrew E. Dolphin, Nicolas F. Martin, Jelte T. A. de Jong, Jon Holtzman, Julianne J. Dalcanton, Karoline M. Gilbert, Benjamin F. Williams, Eric F. Bell, Vasily Belokurov, N. Wyn Evans, 2012, ApJ, 748, 88

"Resolved Near-Infrared Stellar Populations in Nearby Galaxies" Julianne J. Dalcanton, Benjamin F. Williams, Jason. L. Melbourne, Léo Girardi, Andrew E. Dolphin, Philip Rosenfield, Martha L. Boyer, Roelof S. de Jong, Karoline M. Gilbert, Paola Marigo, Knut Olsen, Anil C. Seth, Evan Skillman, 2012, ApJS, 198, 6

"How Typical Are The Local Group Dwarf Galaxies?" Daniel R. Weisz, Andrew E. Dolphin, Julianne J. Dalcanton, Evan Skillman, Jon Holtzman, Benjamin F. Williams, Karoline M. Gilbert, Anil C. Seth, Andrew Cole, Stephanie M. Gogarten, Keith Rosema, Igor D. Karachentsev, Kristen B. W. McQuinn, Dennis Zaritsky, 2011, ApJ, 743, 8

"The ACS Nearby Galaxy Survey Treasury VIII. The Global Star Formation Histories of 60 Dwarf Galaxies in the Local Volume" Daniel R. Weisz, Julianne J. Dalcanton, Benjamin F. Williams, Karoline M. Gilbert, Evan Skillman, Anil C. Seth, Andrew E. Dolphin, Kristen B. W. McQuinn, Stephanie M. Gogarten, Jon Holtzman, Keith Rosema, Andrew Cole, Igor D. Karachentsev, Dennis Zaritsky, 2011, ApJ, 739, 5

"The ACS Nearby Galaxy Survey Treasury VII. The NGC 4214 Starburst and the Effects of Star Formation History on Dwarf Morphology" Benjamin F. Williams, Julianne J. Dalcanton, Karoline M. Gilbert, Anil C. Seth, Daniel R. Weisz, Evan Skillman, Andrew E. Dolphin, 2011, ApJ, 735, 22

"The History of Star Formation in Galaxy Disks in the Local Volume as Measured by the Advanced Camera for Surveys Nearby Galaxy Survey Treasury" Benjamin F. Williams, Julianne J. Dalcanton, L.~C.~Johnson, Daniel R. Weisz, Anil C. Seth, Andrew E. Dolphin, Karoline M. Gilbert, Evan Skillman, Keith Rosema, Stephanie M. Gogarten, Jon Holtzman, Roelof S. de Jong, 2011, ApJ, 734, L22

"The ACS Nearby Galaxy Survey Treasury IX. Constraining Asymptotic Giant Branch Evolution with Old Metal-Poor Galaxies." Léo Girardi, Benjamin F. Williams, Karoline M. Gilbert, Philip Rosenfield, Julianne J. Dalcanton, Paola Marigo, Martha L. Boyer, Andrew E. Dolphin, Daniel R. Weisz, Jason Melbourne, Knut A.G. Olsen, Anil C. Seth, Evan Skillman, 2010, ApJ, 724, 1030.

"SN 2010U: A Luminous Nova in NGC 4214." Roberta M. Humphreys, José L. Prieto, Philip Rosenfield, L. Andrew Helton, Christopher S. Kochanek, K. Z. Stanek, Rubab Khan, Dorota Szczygiel, Karen Mogren, Robert A. Fesen, Dan Milisavljevic, Benjamin Williams, Jeremiah Murphy, Julianne Dalcanton, Karoline M. Gilbert, 2010, ApJ, 718, L43.

"The Advanced Camera for Surveys Nearby Galaxy Survey Treasury. VI. The Ancient Star Formation Disk of NGC 404." Benjamin F. Williams, Julianne J. Dalcanton, K. M. Gilbert, Adrienne Stilp, Andrew E. Dolphin, Anil C. Seth, Daniel Weisz, Evan Skillman, 2010, ApJ, 716, 71.

"The ACS Nearby Galaxy Survey Treasury V. Radial Star Formation History of NGC 300." Stephanie M. Gogarten, Julianne J. Dalcanton, Benjamin F. Williams, Rok Roškar, Jon Holtzman, Anil C. Seth, Andrew E. Dolphin, Daniel Weisz, Andrew Cole, Victor P. Debattista, Karoline M. Gilbert, Knut Olsen, Evan Skillman, Roelof S. de Jong, Igor D. Karachentsev, Thomas R. Quinn, 2010, ApJ, 712, 858

"The ACS Nearby Galaxy Survey Treasury IV. The Star Formation History of NGC 2976." Benjamin F. Williams, Julianne J. Dalcanton, Adrienne Stilp, Karoline M. Gilbert, Rok Roškar, Anil C. Seth, Daniel Weisz, Andrew E. Dolphin, Stephanie M. Gogarten, Evan Skillman, Jon Holtzman, 2010, ApJ, 709, 135

"The NGC 300 Transient: An Alternative Method for Measuring Progenitor Masses." Stephanie M. Gogarten, Julianne J. Dalcanton, Jeremiah W. Murphy, Benjamin F. Williams, Karoline M. Gilbert, Andrew E. Dolphin, 2009, ApJ, 703, 300

"The ACS Nearby Galaxy Survey Treasury." Julianne J. Dalcanton, Benjamin F. Williams, Anil C. Seth, Andrew E. Dolphin, Jon Holtzman, Keith Rosema, Evan D. Skillman, Andrew Cole, Leo Girardi, Stephanie M. Gogarten, Igor D. Karachentsev, Knut Olsen, Daniel Weisz, Charlotte Christensen, Ken Freeman, Karoline Gilbert, Carme Gallart, Jason Harris, Paul Hodge, Roelof S. de Jong, Valentina Karachentseva, Mario Mateo, Peter B. Stetson, Maritza Tavarez, Dennis Zaritsky, Fabio Governato, Thomas Quinn, 2009, ApJS, 183, 67