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

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/dA

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.

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.

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.

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.

Follow-up strategies: Candidate confirmation or Deep Observations?

• Confirmation of a M500=1014 M cluster at z=0.7 at 5-s significance is possible in 4 hours.

• For an M500=3x1014 M 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≥2x1014 M cluster.

• High-resolution, sub-arcminute SZE informs us of the dynamical state of the cluster.

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.

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

4 hr observation of z=0.7, M500 = 3.4 x 1014

M cluster (contours are 2-s, starting at 2- )s

4 hr observation of z=0.7, M500 = 1.9 x 1014

M cluster (contours are 1-s, starting at 2- )s

4 hr observation of z=0.7, M500 = 1.6 x 1014

M cluster (contours are 1-s, starting at 2- )s

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).

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.

Figure from Edward R. Tufte’s The cognitive Style of PowerPoint