Key plots for dark matter astrophysical probes

[yymao]

What is a good figure of merit or a key plot (though maybe we need more than one) for dark matter astrophysical probes that we can show in all the conferences we go to? If we do have a money plot, what would be on the axes?

cc @ahgpeter @kadrlica @andrew-zentner

[kadrlica]

Here's the cartoon that @yymao and I were discussing this evening.

I think we agreed that @yymao and @ahgpeter agreed that a "money plot" was a better idea than a "figure of merit". We also admitted to ourselves that a good (i.e., understandable by the masses) money plot would necessarily sweep a lot of physics under the rug. The goal would be to allow constraints from several different probes (Lyman-alpha, dwarfs, colliding clusters, etc.) to be drawn on the same figure along with "theory blobs" in the background. One thing that we are missing from this figure is a "finish line" (i.e., the thermal cross section for indirect detection or the neutrino floor for direct detection).

[lmoustakas]

I like the use of multiple scales on the top and bottom x-axis, in this example giving the correspondence between a fiducial vanilla warm particle, and something like the characteristic truncation halo mass scale.

I think this could be extended to more quantities as well, and shown as additional floating "axes" above or to the left of the main plot.

In the spirit of the current x-axis plotting choices, a correspondence could also be derived and plotted for

• a characteristic free-streaming scale plotted in another x-axis line (which is a more generic structure consequence of a warm dark matte particle, without assuming that it's thermal, so could apply to axionic or decaying dark matter candidates); and another for

• a characteristic k-cut scale (which would apply to e.g. the position of the first oscillation suppression of dark acoustic oscillations, coming from interacting dark matter candidates).

In this way, this merit plot overall remains the same as it's shown here, while giving it a deeper sense of the ranges of models and measurement types that can be represented.

[wadawson]

The compact halo dark matter folks have been tasked with coming up with an analogous key plot for their constraints. This will likely just be the typical f_dark matter as a function of mass constraint plot.

[kadrlica]

Here's an idea for complementarity with indirect detection searches for dark matter annihilation. The shape and order of the lines is not arbitrary, but it is also not backed up with a quantitative analysis.

Thoughts from @tslatyer @koushiappas @bechtol and @MLisanti?

@MLisanti also suggests including improvements to Galactic dark matter distribution (both for GC blob and constraints from the inner/outer halo).

[kadrlica]

Help @tmptait @tslatyer @aismail3 @esrabulbul! Assuming decay to 2 photons (see Fig 9 in 1309.4091).

This cartoon largely comes from:

• https://arxiv.org/pdf/0811.2385.pdf
• https://arxiv.org/pdf/1309.4091.pdf

But with updates at high energy from:

• https://arxiv.org/abs/1506.00013

The assumption is that LSST can improve the sensitivity of these searches by providing a high resolution map of the dark matter distribution. Cross correlation should increase sensitivity, but I have no idea by how much. (It seems like there should be an easy way to ballpark, perhaps by knowing the mean amplitude/spectrum of density fluctuations a current times.)

Probably clearer to show the individual experiments, like Figure 9:

[tslatyer]

@wadawson In the compact DM case, one could also imagine an axis for degree of "compactness", ranging from primordial black holes through to more extended DM subhalos, if it turns out that adding extension has interesting effects (as per Simona's hack) - but I agree that (halo fraction) vs mass is a simpler starting point.

@kadrlica That sounds reasonable - so you would just pick a couple of sample annihilation/decay channels to display how the different constraints compare? For decay, gamma gamma lets you go down to the lowest masses, but for high DM masses it's not expected to be the strongest channel.

I'm not sure how to forecast how much the cross-correlation measurements would improve, but I'm not an expert on those analyses. Shirasaki et al in 1607.02187 say that LSST would reduce their statistical error by a factor of 13, and at that point the uncertainties would become dominated by systematics due to the subtraction of Galactic foregrounds (they're using gamma-ray data) - so there might be a "foreground floor" of sorts.

I guess for dwarf galaxies the big effect of LSST is to find more dwarfs, so that seems like a relatively easy sensitivity increase to estimate? (albeit with uncertainties on how many new dwarfs will be visible)

[kadrlica]

Here are a set of slides that I've been presenting to emphasize the role of astrophysical probes of dark matter. The first is the conventional slide that particle physicists are used to seeing:

The second shows the role that astrophysical probes play. The emphasis here is that each of the particle physics probes requires some extra coupling between the dark sector and the baryonic sector. Astrophysical probes measure dark matter directly and do not require this coupling.

Everyone is welcome to use these slides or ideas.

[ahgpeter]

A picture I use to explain dark matter in the Universe, and its connection to baryons. Frosting holds the sprinkles on the cupcake, just like dark matter halos hold galaxies together (without dark matter, it is difficult to form galaxies). A version of this appeared in this paper: http://adsabs.harvard.edu/abs/2012arXiv1201.3942P cupcake.pdf Feel free to use, please credit the paper.

[ahgpeter]

A plot Matt Buckley and I made to illustrate the connection between galaxies and halos. The plot has multiple axis labels, including equivalent k if that halo corresponds to the half-mode mass. If you use it, please cite this paper: http://adsabs.harvard.edu/abs/2017arXiv171206615B halos_galaxies_primer_matt.pdf

[kadrlica]

Talking with @MLisanti about direct detection

• Looking at low mass conventional nuclear scattering (possibly order of magnitude changes from knowing velocity distribution)
• Looking at low mass electron scattering (also strongly dependent on f(v))
• Looking at how detection contours will shift from experiment to experiment depending on f(v)
• Understanding f(v) for our Milky Way (i.e., not simulations). This is dependent on merger history. Looking for connections with the stellar halo.

This could be a separate project, or potentially combined into an astroparticle complementarity paper.

[wadawson]

Here is a MACHO summary plot (Carr et al. 2016), outdated but a good idea to have an updated version for the paper.

[kadrlica]

@wadawson do we have a sense of which of these constraints will be improved by LSST? Will LSST be able to improve very low-mass constraints a la HSC observations of M31 (1701.02151)?