Value-Added Research Enabled by High-Level Science Products Hosted at MAST

Anton M. Koekemoer, koekemoer@stsci.edu, and the STScI Archive Team at MAST

The Barbara A. Mikulski Archive for Space Telescopes (MAST) is one of NASA's premier astronomy data centers, along with the High Energy Astrophysics Science Archive Research Center (HEASARC) and the NASA/IPAC Infrared Science Archive (IRSA). MAST is the primary archive repository for data from several large, active space missions (Hubble, Kepler, XMM-OM, and Swift-UVOT); legacy data from past missions (GALEX, FUSE, IUE, EUVE, and others); planned data from future missions, for example, TESS and the James Webb Space Telescope; and all-sky surveys such as VLA-FIRST, GSC and DSS. MAST also provides access to enhanced products accessible via the Hubble Legacy Archive (HLA) and the Hubble Source Catalog (HSC). All current MAST news and updates are posted on our main archive website).

A widely used feature of MAST is our collection of High-Level Science Products (HLSPs, accessible to the entire community at http://archive.stsci.edu/hlsp). These consist of science-ready, fully reduced, publication-quality products—which we receive from teams in the community—for data related to any of the missions supported at MAST, in addition to data from HST Treasury, Archival Legacy, and Large programs (see http://archive.stsci.edu/hst/tall.html). A wide variety of data is available on planets, stars, interstellar medium (ISM), galaxies, active galactic nuclei (AGN), clusters, and many other types of objects, across a wide range of wavelengths spanning radio, infrared (IR), optical, ultraviolet (UV) and X‑ray energies. The data products include full-depth mosaics from large surveys, photometric catalogs, image atlases, spectral atlases, time series lightcurves, spectral linelists, and model simulations, and also include interactive display tools in many cases.

The HLSPs at MAST are ideal for jumpstarting new science, and have gone through expert processing by the original science teams who delivered them to MAST, and who have also been using these products for their own science. Moreover, the quality of the products is attested to by refereed publications from these original science teams, where detailed descriptions are often presented on specialized processing and science validation tests that have been carried out by these teams on their HLSPs. In addition to science results from the original HLSP teams, there are also many examples of new and interesting science by others in the community, extending beyond the goals envisioned in the original proposals. We highlight here a couple of examples, by way of illustrating the diversity of science that is possible with these products.

One example of new science from these datasets is the measurement of the kinematics of the Orion Trapezium cluster (Olivares et al. 2013), where the data used for this project included the products from the HST Orion Treasury Survey (Robberto et al. 2013; with data available at https://archive.stsci.edu/prepds/orion/). The resulting kinematic measurements, derived from a combination transverse and radial velocities, achieve an r.m.s. precision of ∼1 km s-1 per axis and show that at least one of the six components of this cluster is moving at a speed exceeding the escape velocity of the cluster. The remaining cluster members appear to be bound and virialized, hence this is a likely example of ejection of a component from a young star cluster.

Full-color image of the from the HST Orion Treasury Survey (Robberto et al. 2013), which used WFPC3, ACS and NICMOS to carry out an 11-filter imaging survey of the entire region.

Another example of the use of HLSPs for science research beyond the original proposal comes from the Legacy ExtraGalactic Ultraviolet Survey (LEGUS; Calzetti et al. 2015). This Treasury program obtained resolved Hubble imaging in NUV, U, B, V, and I, for 50 nearby galaxies (i.e., closer than ∼12 Mpc). High-resolution UV imaging, not previously available for >90% of the sample, is critical for the age-dating and identification of young massive stars and clusters; accurate reconstruction (∼10 Myr) star-formation histories; and the breaking of the age-extinction degeneracies on small scales. The LEGUS HLSP (available here) allowed the originating team to study the relationships between star formation on two fundamental scales—those of galaxy disks over kiloparsecs, and those of individual stars, stellar clusters and associations over parsecs. LEGUS observations and data products support a wide range of community science, and approximately 50% of the papers published from this data are from authors not on the LEGUS team. Two examples are:

  • Khan et al. (2015) used LEGUS data to examine five η Carinae candidates in nearby galaxies and find that the substantial material resulting from an ejection may have occurred with the onset of carbon burning. This data, with Spitzer observations, suggests the age of this occurrence (∼103–104 years) corresponds with the age of the shells detected.
  • Reynolds et al. (2015) searched LEGUS data for massive stars with M > Msun that may have collapsed without undergoing a dramatic visible SN event were examined in repeated observations of galaxies. The signature provides identification of massive stars that disappear without a bright SN event due to a failed explosive event. LEGUS data were combined with other Hubble observations to identify such massive-star candidates. Of the six candidates identified, one in particular appears to be the site of a core-collapsed, non-SN massive star in NGC 3021.

This figure shows the comparison between the optical and UV LEGUS images of the nearby galaxy NGC 6503, where the older stellar populations and H ii regions visible in the ACS optical filters (F435W, F555W, F658N) can be compared with the bright young stars directly visible in the WFC3/UVIS filters (F275W and F336W). The HLSP website contains interactive displays, including a slider that can be dragged from left to right to directly reveal the UV stars underlying the optical H II regions.

We are always happy to receive new HLSPs that are related to observations obtained with any of the missions we host at MAST. Benefits of hosting HLSPs at MAST include free, permanent, highly visible locations for the data, as well as our ability to tie the data directly into searches made using our archive interfaces (for example the MAST Portal or the Hubble Legacy Archive). We also generally associate a given HLSP dataset with refereed papers provided by the contributing team, which provides additional visibility and citation opportunities for the work done by that team. Large Hubble programs and Archival Treasury programs already commit to delivering HLSPs to MAST, but we also welcome such products from others in the community. Please feel free to contact us by sending us email, or by contacting us on Facebook, Twitter, or our new MAST Forum. We will be glad to discuss options for providing new HLSPs with a high-visibility, permanent home at MAST, or consider any other suggestions about adding further value to the science products available at MAST.

References

Calzetti, D., Lee, J. C., Sabbi, E., et al. 2015, "Legacy Extragalactic UV Survey (LEGUS) with the Hubble Space Telescope. I. Survey Description," AJ, 149, 51

Khan, R., Adams, S. M., Stanek, K. Z., et al. 2015, "Discovery of Five Candidate Analogs for η Carinae in Nearby Galaxies," ApJL, 815, L18

Olivares, J., Sanchez, L. J., Ruelas-Mayorga, A., et al. 2013, "Kinematics of the Orion Trapezium Based on Diffracto-Astrometry and Historical Data," AJ, 146, 106

Reynolds, T. M., Fraser, M., \& Gilmore, G. 2015, "Gone without a Bang: An Archival HST Survey for Disappearing Massive Stars," MNRAS, 453, 2885

Robberto, M., Soderblom, D. R., Bergeron, E., et al. 2013, "The Hubble Space Telescope Treasury Program on the Orion Nebula Cluster," ApJS, 207, 10