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Carnegie Hubble Program (CHP)

The CHP is a program to measure a value of the Hubble constant with a final systematic uncertainty of only 3% by taking advantage of the Spitzer Space Telescope's unique mid-infrared capabilities. This involves using IRAC to undertake a fundamental recalibration of the Cepheid distance scale and progressively moving it out to pure Hubble flow by an application of a revised mid-IR Tully-Fisher relation.

The calibration and application, in one coherent and self-consistent program, will go continuously from distances of parsecs to several hundred megaparsecs. It will provide a first-ever mid-IR calibration of Cepheids in the Milky Way, LMC and HST Key Project spiral galaxies and a first-ever measurement and calibration of the TF relation at mid-infrared wavelengths, and finally a calibration of Type Ia SNe. Most importantly this program will be undertaken with a single instrument, on a single telescope, working exclusively at mid-infrared wavelengths that are far removed from the obscuring effects of dust extinction. Using Spitzer in this focused way will effectively eliminate all of the major systematics in the Cepheid and TF distance scales that have been the limiting factors in all previous applications, including the HST Key Project.

This program, based exclusively on Spitzer data, will deliver a value of the Hubble constant, having a statistical precision better than ±1%, with all currently known systematics quantified and constrained to a level of less than 3%. A value of H0 determined to this level of systematic accuracy is required for up-coming cosmology experiments, including Planck. A more accurate value of the Hubble constant will directly result in other contingently measured cosmological parameters (e.g., Ωm, ΩL, & w) having their covariant uncertainties reduced significantly now. Any further improvements using this route will have to await JWST, for which this study is designed to provide foundation, and ultimately a value of H0 accurate to 2%.

Carnegie news release.

Team members

  • Wendy Freedman (PI)
  • Barry Madore
  • Jane Rigby
  • Eric Persson
  • Violet Mager
  • Laura Sturch
  • Vicky Scowcroft
  • Andy Monson
  • Mark Seibert

CHP Team only project pages (Not yet public. Login required.)

First results from the CHP: poster at the 2010 Winter AAS Meeting.

Getting started

Consult the User's Guide for information on using the wiki software.

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