1. MUSTANG-2 follow-up of eROSITA-selected clusters Tony Mroczkowski 1, Jon Sievers 2, Nick Battaglia 3, Brian Mason 4, Charles Romero 4, Mark Devlin 5, Alex Young 5, Simon Dicker 5, Erik Reese 5, Justus Brevik 6, Sherry Cho 6, Kent Irwin 6, Jeff McMahon 7 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 Y sz provides a valuable mass scaling relation. Y sz falls off as 1/d A 2, 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’s resolution (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 M 500 =10 14 M  cluster at z=0.7 at 5-  significance is possible in 4 hours. For an M 500 =3x10 14 M  h -1 cluster 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 r 500 of a M 500 ≥2x10 14 M  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. M 500 = (1.6, 1.9, 3.4, 7.8) x 10 14 M  (from left to right). Red line marks r 500. Radially-averaged SZE signal is non- zero beyond r 500. Uncertainty from the primary CMB is not shown.

8. 4 hr observation of z=0.7, M 500 = 7.8 x 10 14 M  cluster (images smooth to 8.3”; contours are spaced by 2- , starting at 2- 

9. 4 hr observation of z=0.7, M 500 = 3.4 x 10 14 M  cluster (contours are 2- , starting at 2- 

10. 4 hr observation of z=0.7, M 500 = 1.9 x 10 14 M  cluster (contours are 1- , starting at 2- 

11. 4 hr observation of z=0.7, M 500 = 1.6 x 10 14 M  cluster (contours are 1- , starting at 2- 

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’s The cognitive Style of PowerPoint