Feb 262014

The Jansky-VLA Legacy Survey of the Frontier Fields will provide deep (1uJy/bm) dual-band (3 and 6 GHz) imaging over the full HST and Spitzer coverages for the lensing cluster fields MACSJ0717, MACS1149, and MACS0416.

Using the Very Large Array in both A- and C-configurations, we will generate maps having 0.65 and 0.33 arc-second resolution, respectively.  These deep images will have a significant and lasting impact for the coming decades, providing unique observations that will be used to:

  • Study the relationship between star formation, radio spectral index, and starburst size for galaxies on and off the main sequence out to z ~ 5, at high spatial resolution using a wavelength immune to the effects of obscuring dust.
  • Track the co-evolution of AGN and star-formation as a function of redshift through robust measurements of the brightness temperature, radio spectral index, and polarization of nuclear emission in hundreds of galaxies spanning more than two orders of magnitude in luminosity.
  • Characterize the distribution of star formation on sub-kpc scales within disk galaxies at z > 1, which is only achievable as a result of the magnification provided by the lensing clusters.
  • Detect Milky Way-like galaxies in the intermediate redshift lensing clusters, yielding a census of star formation as a function of environment when quenching in clusters was most efficient.

Once the final two Frontier Fields are approved, we plan to complete the survey by additionally mapping the remaining Frontier Fields that are accessible to the VLA (i.e., Abell 2744 and Abell 370).


VLA coverage at 3 GHz (black circles) and 6 GHz (magenta circles), vs. the HST WFC3/IR and ACS pointings for the clusters (red and blue center boxes) and parallel fields (outer boxes).

Legacy Value:
These data will have a lasting legacy value for the community for years to come and undoubtedly contribute to a large number of Ph.D. theses studying the radio properties of galaxies and galaxy evolution in general. For instance, this program will explore an uncharted region of observational parameter space (e.g., the polarized sky at uJy levels) by making the deepest map towards a massive cluster at these frequencies, yielding the possibility of finding new classes of intrinsically faint sources and almost certainly leading to community-led science projects that are beyond those described above (e.g., stacking analyses to improve detection limits for the highest redshift sources and confirm UV-radio star formation rate conversions as a function of redshift and luminosity).

These radio observations will also provide some of the deepest cosmological radio data ever taken. The proposed 1 uJy RMS depth at 3 GHz is a factor of 2 and 1.5 times deeper than current/ongoing observations of COSMOS (2 uJy at 3GHz) and GOODS-N (2.5 uJy at 1.4GHz), respectively, even before lens amplification.

Eric Murphy
PI of the Jansky-VLA Legacy Survey of the Frontier Fields
U.S. Planck Data Center, IPAC Pasadena, CA

 Posted by at 5:06 pm
Feb 052014

Nicolas Laporte and collaborators have compared the deep HST images of Frontier Fields cluster Abell 2744 to 50 hours of Spitzer IRAC imaging.  One of the best candidates for a distant z~8 galaxy — detected in the HST  WFC3/IR images — disappears in the IRAC 3.6 micron image and reappears in the IRAC 4.5 micron image.   The best explanation for these strange colors is the appearance of very strong emission lines from oxygen and hydrogen ([OIII] and H-beta) which fall into the 4.5 micron band at a redshift of z~7.98.

The paper has been accepted for publication in the A&A Letters.

Check out the details: http://arxiv.org/abs/1401.8263v1.

JWST will be able to provide conclusive observations with both NIRSpec and NIRCam grism observations.  Bring on 2018 and the launch of JWST!

 Posted by at 12:37 pm