MUSTANG-2 follow-up of eROSITA -selected clusters

1. MUSTANG-2 follow-up of eROSITA-selected clusters Tony Mroczkowski1, Jon Sievers2, Nick Battaglia3, Brian Mason4, Charles Romero4, Mark Devlin5, Alex Young5, Simon Dicker5, Erik Reese5, Justus Brevik6, Sherry Cho6, Kent Irwin6, Jeff McMahon7 1 - NASA Einstein Postdoctoral Fellow, Caltech/JPL, 2 - Princeton University, 3 - Carnegie Mellon University, 4 - NRAO, University of Virginia, 5 - University of Pennsylvania, 6 -NIST, 7 - University of Michigan

2. Some benefits of SZE follow-up • Independent confirmation is intrinsically valuable (e.g. for testing the purity of the EASS sample). • The thermal SZE is highly complementary to X-ray observations. • The integrated SZE signal Ysz provides a valuable mass scaling relation. • Ysz falls off as 1/dA2, meaning it is only diminished to half its z=0.5 value when scaled to the turnaround in angular diameter distance. • By this point in the session, probably all this has been well-covered in the preceding talks. The important point for MUSTANG-2 is that its strength will be in targeted follow-up. • MUSTANG-2’s 9” measurements of the SZE will be particularly useful for confirming and probing the astrophysics of high-z cluster candidates, where eROSITA’sresolution (28” average) will make separation of AGN from ICM X-ray emission difficult. • Ground-based follow-up at radio wavelengths is a relatively inexpensive way to confirm the same gas seen in X-rays.

3. The 100-m Green Bank Telescope • 9” resolution at 90-GHz. • largest steerable structure on the ground; stands 148m tall. • collecting area is comparable to the full ALMA+ACA, and nearly an order of magnitude more than CARMA-23. Green Bank, WV offers ~60 nights per year with conditions suitable for 90-GHz observations.

4. MUSTANG-1.5 • Horn-coupled, to improve signal per detector over the current (bare) MUSTANG-1 array (M-1). • Wider bandwidth than M-1 will further increase signal per detector. • Upgrades will use a scaled version of the transition edge sensors (TES) in ACTpol and SPTpol, which have a demonstrated lower intrinsic noise than the M-1 detectors. • Each detector is expected to be ~4-6 times more sensitive than the ~30 good detectors in a typical M-1 observation. • M-1.5 is now being built. M-1.5 will have at least 32 detectors and will be commissioned in Winter 2013/2014.

5. MUSTANG-2 (M-2) • M-1.5’s readout will use a microwave-MUX technology, allowing hundreds of detectors to be read out in frequency space on a single readout line. This will enable M-2 upgrades – as a drop in replacement – using the same readout system and wiring as M-1.5. • M-2’s large 5.8’ instantaneous field of view will probe scales up to 10’ (vs. ~1’ with M-1). The 42” field of view of M-1 has been its primary limitation. • Full 367 dual-polarization M-2 could be ready by Spring 2015 (depending on funding). M-2 will offer mapping speeds several hundred times faster than M-1.

6. Follow-up strategies: Candidate confirmation or Deep Observations? • Confirmation of a M500=1014 Mcluster at z=0.7 at 5-ssignificance is possible in 4 hours. • For an M500=3x1014M h-1cluster at z=0.7, this would take < 7 minutes. • Higher significance detections of the ~1000 most massive clusters at z≥0.8 could provide strong constraints on non-Gaussianity (Pillepich et al. 2012). • Deeper observations can probe beyond r500 of a M500≥2x1014Mcluster. • High-resolution, sub-arcminute SZE informs us of the dynamical state of the cluster.

7. Radially-averaged SZE surface brightness profile from mock M-2 observations • 4 hr observations of four z=0.7 clusters, from the simulations of Battaglia et al. 2010. • M500 = (1.6, 1.9, 3.4, 7.8) x 1014 M(from left to right). • Red line marks r500. • Radially-averaged SZE signal is non-zero beyond r500. • Uncertainty from the primary CMB is not shown.

8. 4 hr observation of z=0.7, M500 = 7.8 x 1014 Mcluster (images smooth to 8.3”; contours are spaced by 2-s, starting at 2-s.)

9. 4 hr observation of z=0.7, M500 = 3.4 x 1014 Mcluster (contours are 2-s, starting at 2-s)

10. 4 hr observation of z=0.7, M500 = 1.9 x 1014 Mcluster (contours are 1-s, starting at 2-s)

11. 4 hr observation of z=0.7, M500 = 1.6 x 1014 Mcluster (contours are 1-s, starting at 2-s)

12. Example: Source-subtraction from a MUSTANG-1 observation • It has been claimed that radio source contamination cannot be removed from bolometric observations. This is no longer the case. • In Mroczkowski et al. 2012 (see http://arxiv.org/abs/1205.0052), we removed an extended source from the MUSTANG-1 time-ordered data using an iterative procedure. This slightly changes the noise estimates, but does not alter the SZE features. • Other procedures exist and are maturing for bolometric data (e.g. CLEAN or model-fitting in time streams).

13. Summary/Future Work • MUSTANG-1.5 will be commissioned in 1 year (Winter 2013/2014), and will offer 4-6x the sensitivity of MUSTANG-1 and probe scales up to 3’ (at the same 9” resolution). • MUSTANG-2 will be a straight-forward upgrade from M-1.5, and could be online by 2015, in time to confirm hundreds of massive, high-z clusters discovered in the EASS. It will probe scales up to 10’, and be 20-30x more sensitive than M-1. • Deep observations with M-2 could be used to study dynamics, pressure substructure, or (in conjunction with the X-ray data) derive the Hubble constant.

14. Figure from Edward R. Tufte’sThe cognitive Style of PowerPoint