Compact Dark Matter with Globular Cluster Pulsars
summary
The gist
The gist The number of detectable transits is set by the integral over the dark-matter density along the line of sight connecting the Earth and the pulsar How it works The search for compact dark
In short
The study searches for compact dark matter using pulsars by measuring a Shapiro delay caused by a passing compact object's gravitational field. It ranks globular clusters, specifically Terzan 5, as prime targets due to high dark matter columns. By using the Square Kilometre Array (SKA2) sensitivity, the authors project that this search could detect dark matter making up $6\%$ of the local dark matter at a mass of $0.02 M_{\odot}$.
Key concepts
- Shapiro Delay
- This is a timing shift in a pulsar's signal caused by a compact object, like dark matter, passing near the line of sight. The object's gravity bends the spacetime around it, causing the pulses to be delayed as they travel past this gravitational potential well.
- Dark-Matter Column ($\Sigma$DM)
- This is a key measure for the search; it represents the total amount of dark matter mass per unit area along the line connecting Earth and a pulsar. The more dark matter in this column, the greater the chance of detecting a signal from compact objects passing through it.
- Compact-Baryon Floor
- This concept quantifies the background noise created by ordinary stars and stellar remnants within Terzan 5 and along the line of sight. It represents a minimum dark matter fraction that would produce the same number of observable transits as the actual foreground objects.
Terminology used across episodes
This episode discusses
- Compact Dark Matter with Globular Cluster Pulsars · Paper Radio
- Primordial Black Holes as Dark Matter
- Constraints on Primordial Black Holes
- Primordial Black Holes as Dark Matter: Recent Developments
- Primordial Black Holes as a dark matter candidate
- Primordial Black Holes
- Searching for primordial black hole dark matter with pulsar timing arrays
- Probing Dark Matter Substructure with Pulsar Timing
- Prospects for Detecting Dark Matter Halo Substructure with Pulsar Timing
- Enhanced exploration for primordial black holes using pulsar timing arrays
- Pulsar timing signal from ultralight scalar dark matter
- Pulsar timing can constrain primordial black holes in the LIGO mass window
- Stochastic Ultralight Dark Matter Fluctuations in Pulsar Timing Arrays
- Pulsar Timing Probes of Primordial Black Holes and Subhalos
- Observability of Dark Matter Substructure with Pulsar Timing Correlations
- Bayesian Forecasts for Dark Matter Substructure Searches with Mock Pulsar Timing Data
- Discovery and timing of ten new millisecond pulsars in the globular cluster Terzan 5
- Using long-term millisecond pulsar timing to obtain physical characteristics of the bulge globular cluster Terzan 5
- Discovery of three new millisecond pulsars in Terzan 5
- A Novel Technique for Long-term Timing of Redback Millisecond Pulsars
- A Fourier Domain "Jerk" Search for Binary Pulsars
The paper
Compact Dark Matter with Globular Cluster Pulsars · Read on arXiv
Soobeom Chung, Jeff A. Dror
Institute for Fundamental Theory, Physics Department, University of Florida
Pulsars are exceptionally stable clocks, and a compact dark-matter object passing near the line of sight to a pulsar delays its pulses through the Shapiro effect. The number of detectable transits is set by the integral over the dark-matter density along the line of sight connecting the Earth and the pulsar. Established pulsars in pulsar timing arrays are typically within one kiloparsec of the Earth and hence sit in a dark-matter density comparable to our local value. In this work, we explore globular clusters in the inner Galaxy as targets to search for compact dark matter. These high-pulsar-density environments can be cheaply observed with a single telescope beam and enjoy a large dark-matter crossing rate. Additionally, since the recently detected nanohertz gravitational-wave background is nearly common to the cluster's pulsars, a multi-pulsar analysis can remove much of its contribution. Ranking known clusters, we find that Terzan 5, with 49 pulsars, offers the best reach. A forty-year campaign of weekly four-hour visits at the sensitivity envisioned for the second phase of the Square Kilometre Array (SKA) would probe compact objects making up 6% of the dark matter at 0.02,M. Finally, we estimate the foreground from stars and stellar remnants in Terzan 5 and along the sightline. It is subdominant near the most sensitive low-mass part of the SKA benchmark, but becomes important over parts of the stellar mass range.
Transcript
Introduction to the show: ident: Astrophysics Radio. Generated commentary on the latest astrophysics papers.
Vera: I'm Vera.
Jocelyn: And I'm Jocelyn, here with Subrahmanyan.
Vera: We're looking at the paper: "Compact Dark Matter with Globular Cluster Pulsars".
Jocelyn: The gist The number of detectable transits is set by the integral over the dark-matter density along the line of sight connecting the Earth and the pulsar How it works…
Vera: First, who's behind it and why it matters.
Paper summary: Vera: So to recap, this paper "Compact Dark Matter with Globular Cluster Pulsars" explores using pulsars in globular clusters as targets to search for compact dark matter >
Jocelyn: The core thesis is that a compact object passing near the line of sight creates a measurable delay in the pulsar's pulse arrival time through the Shapiro effect, and we can count how many of these transits are expected based on the total dark matter density along that path >
Subrahmanyan: And they argue that globular clusters in the inner Galaxy are excellent targets because they have high pulsar density environments which means a large dark-matter crossing rate >
Vera: They then specifically look at Terzan five ranking it as the best target with forty-nine pulsars, and using this environment to estimate a compact-baryon floor from known stars and remnants along the sightline > <ref:2610.20732#pg1>
Jocelyn: The paper also addresses the nanohertz gravitational-wave background that plagues pulsar timing arrays by suggesting that because the pulsars in a cluster are close together, we can analyze them as a group to remove much of that common background noise >
Subrahmanyan: This whole line of reasoning connects the local density environments to a specific search strategy for dark matter particles >
Vera: And finally, they present projected sensitivity limits across different telescope capabilities, showing how SKA2 could extend the reach by a further order of magnitude >
Jocelyn: It suggests that even with these foregrounds and backgrounds, dedicated timing programs on component normalization scale length and height are necessary to realize these prospects >
Conclusion: Vera: So looking at the paper "Compact Dark Matter with Globular Cluster Pulsars" by Chung and Dror, the main implication is that we have a way to look for dark matter that isn't just relying on signals from distant objects or large-scale structure >
Jocelyn: It’s about using extremely stable clocks like pulsars in dense stellar environments to probe the immediate gravitational environment around them >
Subrahmanyan: For structure formation, this suggests that the local density of dark matter isn't just something we measure on a large scale, but that compact objects could be influencing the distribution of dark matter within clusters themselves >
Vera: And for someone who only listens to the show, it means they're looking at how dense stuff in our galaxy affects the ability to find these small, compact dark matter candidates >
Jocelyn: It’s a concrete search strategy that moves from general gravitational wave detection toward finding specific compact mass candidates through timing residuals >
Subrahmanyan: The paper's focus on Terzan five and the compact-baryon floor gives a clearer picture of how structure within our galaxy affects these searches for dark matter particles > <ref:2610.20732#pg1>
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