DDA 2015 – New Trans-Neptunian Objects in the Dark Energy Survey Supernova Fields

This is one of a series of notes taken during the 2015 meeting of the AAS Division on Dynamical Astronomy, 3-7 May, at CalTech. An index to this series (all the papers presented at the meeting) is here.

David W. Gerdes (U. Michigan)

Abstract

The Dark Energy Survey (DES) observes ten separate 3 sq. deg. fields approximately weekly for six months each year. Although intended primarily to detect Type Ia supernovae, this data set provides a rich time series that is well suited for the detection of objects in the outer solar system, which move slowly enough that they can remain in the same field of view for weeks, months, or even across multiple DES observing seasons. Because the supernova fields have ecliptic latitudes ranging from -15 to -45 degrees, DES is particularly sensitive to the dynamically hot population of Kuiper Belt objects, as well as detached/inner Oort cloud objects. Here I report the results of a search for new trans-Neptunian objects in the first two seasons of DES data, to limiting magnitudes of r~23.8 in the eight shallow fields and ~24.5 in the two deep fields. The 22 objects discovered to date include two new Neptune trojans, a number of objects in mean motion resonances with Neptune, two objects with orbital inclinations above 45 degrees, a Uranian resonator, and several distant scaRered disk objects including one with an orbital period of nearly 6000 years. This latter object is among the half-dozen longest-period trans-Neptunian objects known, and like the other such objects has an argument of perihelion near zero degrees. I will discuss the properties and orbital dynamics of objects discovered to date, and will also discuss prospects for extending the search to the full 5000 sq. deg. DES wide survey.

Notes

  • Piggy back on DES to find and characterizeTNOs
    • Will surpass all previous TNO surveys
    • DECam:
      • 570 Mpix imager
      • CTIO 4-meter
      • 3 deg fov
      • first light Sep. 2012
      • first two of five seasons complete
      • 125 nights/yr, 5 optical bands
      • 60 2k$\times$4k CCDs (two died)
    • Biased towards high inclination objects
      • Sensitive to hot population
  • New objects identified via difference imaging
    • Confusion an issue
    • But KBOs move slowly
    • Once you find a 3-visit orbit consistent with KB motion, it’s easy
    • Should be able to discover a ~600 km object at 80 AU
    • 23 new objects discovered in first two seasons (~10% of hot population)
  • Case studies
    • 2013RG98
      • 3:4 Uranian MMR (temporary)
      • Likely to become a Jupiter family comet, or maybe ejected
    • 2014QO441, 2014QP441
      • Neptune Trojans
      • libration period ~9100 yr
      • stable on Gyr timescales
    • 2013RF98
      • An extreme TNO
      • $a = 325$ AU, $i = 30^\circ$, $e = 0.89$, $P = 5682$ yr
    • Clustering of $\omega$

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