Flashlights: Properties of Highly Magnified Images Near Cluster Critical Curves in the Presence of Dark Matter Subhalos

Williams, Liliya L. R.; Kelly, Patrick L.; Treu, Tommaso; Amruth, Alfred; Diego, Jose M.; Li, Sung Kei; Meena, Ashish K.; Zitrin, Adi; Broadhurst, Thomas J.; Filippenko, Alexei V.

doi:10.3847/1538-4357/ad1660

Cited by 10 publications

(1 citation statement)

References 43 publications

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“…In the situation of recurring microlensing brightening events in the same lensed galaxy, the feasibility to significantly constrain intrinsic and extrinsic parameters can help us determine which caustic-crossing events are associated with the same source star. This knowledge would be useful in realizing highly magnified stars as a novel dark matter probe, such as uncovering star-free subgalactic cold dark matter halos through astrometry (Dai et al 2018;Abe et al 2023;Williams et al 2024) or dense minihalos composed of QCD axion particles as the dark matter (Dai & Miralda-Escudé 2020;Xiao et al 2021).…”

Section: Discussionmentioning

confidence: 99%

Under Einstein’s Microscope: Measuring Properties of Individual Rotating Massive Stars from Extragalactic Microcaustic Crossings

Han,

Dai

2024

ApJ

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Highly magnified stars residing in caustic crossing lensed galaxies at z ≃ 0.7–1.5 in galaxy cluster lensing fields inevitably exhibit recurrent brightening events as they traverse a microcaustic network cast down by foreground intracluster stars. The detectable ones belong to nature’s most massive and luminous class of stars, with evolved blue supergiants being the brightest ones at optical wavelengths. Considering single stars in this work, we study to what extent intrinsic stellar parameters are measurable from multifilter light curves, which can be obtained with optical/near-IR space telescopes during one or multiple caustic crossing events. We adopt a realistic model for the axisymmetric surface brightness profiles of rotating O/B stars and develop a numerical lensing code that treats finite source size effects. With a single microcaustic crossing, the ratio of the surface rotation velocity to the breakup value is measurable to a precision of ∼0.1–0.2 for feasible observation parameters with current space telescopes, with all unknown intrinsic and extrinsic parameters marginalized over and without a degeneracy with inclination. Equatorial radius and bolometric luminosity can be measured to 1/3 and 2/3 of the fractional uncertainty in the microcaustic strength, for which the value is not known at each crossing but an informative prior can be obtained from theory. Parameter inference precision may be further improved if multiple caustic crossing events for the same lensed star are jointly analyzed. Our results imply new opportunities to survey individual massive stars in star formation sites at z ≃ 0.7–1.5 or beyond.

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Section: Discussionmentioning

confidence: 99%

Under Einstein’s Microscope: Measuring Properties of Individual Rotating Massive Stars from Extragalactic Microcaustic Crossings

Han,

Dai

2024

ApJ

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El Gordo needs El Anzuelo: Probing the structure of cluster members with multi-band extended arcs in JWST data

Galan,

Caminha,

Knollmüller

et al. 2024

A&A

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Gravitational lensing by galaxy clusters involves hundreds of galaxies over a large redshift range and increases the likelihood of rare phenomena (supernovae, microlensing, dark substructures, etc.). Characterizing the mass and light distributions of foreground and background objects often requires a combination of high-resolution data and advanced modeling techniques. We present the detailed analysis of a prominent quintuply imaged dusty star-forming galaxy ($ mainly lensed by three members of the massive galaxy cluster ACT-CL\,J0102$-$4915, also known as d =0.87$). We leverage JWST/NIRCam images, which contain lensing features that were unseen in previous HST images, using a Bayesian, multi-wavelength, differentiable and GPU-accelerated modeling framework that combines (lens modeling) and (field model and inference) software packages. For one of the deflectors, we complement lensing constraints with stellar kinematics measured from VLT/MUSE data. In our lens model, we explicitly include the mass distribution of the cluster, locally corrected by a constant shear field. We find that the two main deflectors (L1 and L2) have logarithmic mass density slopes steeper than isothermal, with $ L1 and $ L2 We argue that such steep density profiles can arise due to tidally truncated mass distributions, which we probe thanks to the cluster lensing boost and the strong asymmetry of the lensing configuration. Moreover, our three-dimensional source model captures most of the surface brightness of the lensed galaxy, revealing a clump with a maximum diameter of $400$ parsecs at the source redshift, visible at wavelengths $ rest mu m. Finally, we caution on using point-like features within extended arcs to constrain galaxy-scale lens models before securing them with extended arc modeling.

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Spectroscopic characterisation of gravitationally lensed stars at high redshifts

Lundqvist,

Zackrisson,

Hawcroft

et al. 2024

A&A

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Deep imaging of galaxy cluster fields have in recent years revealed tens of candidates for gravitationally lensed stars at redshifts $z 1$--6, and future searches are expected to reveal highly magnified stars from even earlier epochs. Multi-band photometric observations may be used to constrain the redshift, effective temperature $T_ eff $, and dust attenuation along the line of sight to such objects. When combined with an estimate of the likely magnification, these quantities may be converted into a constraint on the stellar luminosity and, for an adopted set of stellar evolutionary tracks, the initial stellar mass. Further characterisation is difficult, however, without spectroscopic observations, which at the typical brightness levels of high-redshift lensed stars becomes extremely challenging for even the largest existing telescopes. Here, we explore what spectral features one can realistically hope to detect in lensed stars with peak brightness in the range 26--28 AB mag, $T_ eff = 4000$--50\,000 K, and redshifts $z=$1--10, using spectroscopy with JWST and the forthcoming ELT. We find that a majority of detectable lines appear in the rest-UV range for stars with $T_ eff K. The strongest detectable spectral lines are the C IV line and the Si IV 1403AA -doublet at $T_ eff =30\,000$ K. For lower temperatures, the calcium H- and K-lines at $T_ eff =6000$ K are among the most readily detectable. In limited wavelength ranges, ELT is expected to provide more sensitive spectroscopic observations, and with higher resolution than JWST. We find that variations in both mass-loss rate and metallicity lead to noticeable effects in the detectability of certain spectral lines with both JWST and ELT.

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Flashlights: Properties of Highly Magnified Images Near Cluster Critical Curves in the Presence of Dark Matter Subhalos

Cited by 10 publications

References 43 publications

Under Einstein’s Microscope: Measuring Properties of Individual Rotating Massive Stars from Extragalactic Microcaustic Crossings

Under Einstein’s Microscope: Measuring Properties of Individual Rotating Massive Stars from Extragalactic Microcaustic Crossings

El Gordo needs El Anzuelo: Probing the structure of cluster members with multi-band extended arcs in JWST data

Spectroscopic characterisation of gravitationally lensed stars at high redshifts

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