High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Is the coexistence of strange quark stars and hadronic stars favored by astrophysical data? A Bayesian analysis
Luca Passarella, Mirco Guerrini, Giuseppe Pagliara et al. (+2 more)
Hadronic
stars and strange
quark stars could coexist within the so-called two-families scenario. In this respect, hadronic matter and strange
quark matter correspond to two distinct
equilibrium phases described by two different equations of state. We perform here the first detailed
Bayesian analysis that makes use of astrophysical and laboratory data in order to constrain the equations of state adopted within the two-families scenario for hadronic and strange
quark matter. In particular, in hadronic matter we consider the possible formation of hyperons and delta resonances (beside nucleons) within a class of non linear relativistic mean field models and in
quark matter we consider the possible formation of a color-superconducting phase within a bag-like model. Results of the analysis indicate that while at the moment both the one-family and the two-families scenarios are compatible with the data, by comparing the Bayes factors of both models, the two-families scenario is favored with respect to the one-family scenario. Specifically, the two-families framework naturally relieves the tension between the intermediate-density softness of the equation of state required by small-radius objects and the high-density stiffness needed to support massive
pulsars. Ultimately, future detections of even more massive compact objects, very compact ordinary-mass objects, or precise measurements of two distinct masses with the same radius, will provide strong indications in favor of the two-families scenario.
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All authors Luca Passarella, Mirco Guerrini, Giuseppe Pagliara, Andrea Lavagno, Alessandro Drago
High Energy Astrophysical Phenomena
The Fundamental Planes of Black Hole Activity for High-Synchrotron-Peaked BL Lacertae Objects
Qing-Chen. Long, Ai-Jun. Dong and Qi-Jun.Zhi
The
radio–X-ray correlation and Fundamental Plane (FP) of black hole activity can serve as a diagnostic tool for the origin of X-ray emissions. There was a scaling relation between
radio and X-ray emissions for High-synchrotron-peaked BL Lacertae objects (HBLs), i.e., $L_{\rm{R}}\propto L_{\rm{X}}^{0.64}$, which can be explained by ADAF-dominated mode or synchrotron cooling (Syn-c). However, many results of studying blazar physics show that the X-ray emissions of HBLs are mainly produced by the synchrotron process of jets. Therefore, Syn-c appears to provide a plausible explanation for this relation. To further clarify the origin of X-ray emissions of HBLs, we constructed a sample containing 69 HBLs in this paper to re-investigate their
radio–X-ray correlation and FP. Considering the Doppler beaming effect, we find that the intrinsic
radio–X-ray correlation and FP of HBLs are $L_{\rm R,int}\propto L_{\rm X,int}^{0.68}$ and $\log L_{\rm R,int}=(0.57\pm0.06)\log L_{\rm X,int}+(0.33\pm0.11)\log M_{\rm BH}+(12.65\pm2.00)$, respectively. Our results agree with the scaling relation mention above, which suggests these scaling relations are not artificial. By employing the theoretical model of Syn-c, we find that these shallow
radio–X-ray correlations and FP are caused by Syn-c, which implies that the X-ray emissions of HBLs may be produced by rapidly cooling, high-energy electrons accelerated at a shock. This is consistent with results of the recent X-ray polarization observations of HBLs. Our results provide the observational evidence of $L_{\rm R}\propto L_{\rm X_{\text{Syn-c}}}^{0.6\sim0.7}$.
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Solar and Stellar Astrophysics
XP-TEAL: Gaia XP Tool for Emission and Absorption Lines II. Gaia-HELIX catalogue of H$\alpha$ emitters in Gaia BP/RP spectra
S. Malhotra, M. Weiler, F. Anders et al. (+8 more)
Context: With
Gaia's third Data Release (DR3), low-resolution BP/RP (XP) spectra became available for more than 219 million sources. In previous work, we developed a fast method for detecting absorption and emission lines while measuring their equivalent widths directly from the XP spectral coefficients. Aims: We conduct a systematic search for H$\alpha$ emitters in the
Gaia DR3 XP spectra. Methods: We measured the equivalent width of the Balmer H$\alpha$ line for all sources with
Gaia XP spectra and selected an initial sample of 556100 sources depicting an H$\alpha$ emission-like feature at $2\sigma$ level or above. Using a semi-supervised classifier complemented by manual spectral labelling, we removed sources that merely masqueraded as emission-line
stars. Results: We find that 95% of the initial candidates are most likely cool M-type
stars, where a molecular absorption band gives rise to a local maximum that can mimic H$\alpha$ emission. Subsequently, 28394 sources were flagged as bona fide H$\alpha$ emitters using the
Gaia DR3 XP spectra. The majority are Be-like candidates (26287), M-type emission-line
stars (717), Herbig Ae/Be candidates (525), quasi-
stellar objects (204), Wolf-Rayet
stars (177), cataclysmic variables (51), and carbon
stars (18), among other sources. Our equivalent widths and
stellar classifications agree well with results from higher-resolution studies and recent
Gaia XP spectra-based catalogues. Ground-based spectroscopic follow-up for some of the newly found H$\alpha$ emitters reinforces our confidence in the catalogue.
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All authors S. Malhotra, M. Weiler, F. Anders, J. M. Carrasco, G. Garcia-Moreno, C. Jordi, N. Blagorodnova, A. Castro-Ginard, J. Castañeda, F. Boix, X. Luri
High Energy Astrophysical Phenomena
A New Scaling of Neutron Star Tidal Deformability for Directly Probing the Central Equation of State Parameter
Jian-Hao Shi, Bao-Jun Cai, Bao-An Li et al. (+1 more)
The dimensionless
tidal deformability, $\Lambda$, of
neutron stars (NSs), inferred from gravitational-wave (GW) observations, has thus far been used primarily to constrain the pressure of dense matter near twice
nuclear saturation density, leaving the core equation of state (EOS) largely inaccessible to inspiral-phase GW observations. We show that a fundamental central EOS parameter can be probed directly through $\Lambda$ using a perturbative analysis of the dimensionless
stellar-structure and
tidal-response equations formulated in terms of scaled intrinsic variables, without invoking any specific EOS model. We uncover a remarkable EOS-insensitive scaling relation between $\Lambda$ and the central EOS parameter $\rm{X}\equiv P_{\rm c}/\varepsilon_{\rm c}$, where $P_{\rm c}$ and $\varepsilon_{\rm c}$ denote the central pressure and energy density, respectively. The relation is validated against a broad ensemble of physically viable EOSs. Applying it to
tidal deformabilities inferred from events such as GW170817 enables a direct determination of $\rm{X}$. By adopting the previously established effective upper bound $\rm{X}\lesssim0.381$, we infer a tight lower bound, $\Lambda_{\rm{TOV}}\gtrsim9.1^{+0.5}_{-0.5}$, for maximum-mass NSs along stable mass-radius sequences, quantitatively demonstrating that even the most compact stable NSs remain distinctly separated from black holes, for which $\Lambda_{\rm{BH}}=0$. These findings reveal a previously unrecognized connection between inspiral-phase
tidal deformability and the central EOS parameter $\rm{X}$, establishing a direct link between GW observables and the microphysics of ultradense matter in the strong-
gravity regime. The resulting scaling establishes inspiral-phase
tidal deformability as a direct and largely model-insensitive probe of the central EOS parameter $\rm{X}$, and hence of key properties of NS cores.
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All authors Jian-Hao Shi, Bao-Jun Cai, Bao-An Li, Yu-Gang Ma
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Theoretical consistency and phenomenology of supercooled cosmological phase transitions
Maciej Kierkla
This dissertation investigates a supercooled phase transition (PT) in the early Universe. Using high-temperature dimensional reduction (DR), we compute the NLO thermal bubble nucleation rate. By explicitly evaluating fluctuation determinants, we provide a state-of-the-art description of thermal bubble nucleation. As a case study, we consider the SU(2)cSM, an extension of the conformal Standard Model with an additional SU(2)$_X$ gauge sector and scalar field that acquires a vev through radiative
symmetry breaking. This
symmetry breaking proceeds via a supercooled first-order phase transition. The first part of the thesis introduces the theoretical framework, including effective actions, RG improvements, finite-temperature
quantum field theory, effective field theory techniques, and thermal bubble nucleation. The second part applies these methods to the SU(2)cSM. We establish a consistent power-counting scheme, construct the leading-order effective potential, analyse
symmetry breaking and parameter space, derive an RG-improved potential, and incorporate thermal corrections. We then apply high-temperature DR to a classically scale-invariant model for the first time, derive the corresponding three-dimensional EFT, and compute the NLO nucleation rate. A detailed numerical evaluation of fluctuation determinants enables a comparison of different approximation schemes and their limitations. Finally, we present the phenomenological implications. We determine phase transition parameters, perform parameter scans, and predict the resulting gravitational wave signals. We find that the supercooled phase transition in the SU(2)cSM produces a strong signal detectable by LISA throughout the parameter space considered, making the model experimentally testable. We also demonstrate that higher-order corrections can significantly affect both phase transition dynamics and gravitational wave predictions.
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Astrophysics of Galaxies
Extended [CII] gas emission in and around a massive quiescent galaxy at z=7.3
F. Valentino, A. Pensabene, A. Weibel et al. (+16 more)
We report the discovery of [CII] 158 micron emission in and around the most distant known massive quiescent
galaxy RUBIES-UDS-QG-z7 at z = 7.27. Observed with ALMA in band 6, the [CII] line independently confirms the spectroscopic
redshift from JWST/NIRSpec spectra at low and medium resolution. The emission extends over an effective radius R_eff,[CII] = 8 +/- 3 kpc, well beyond the compact
stellar body traced by JWST/NIRCam (R_eff = 209 (+33/-24) pc), with a significant fraction of approximately 70% of the flux arising from a circumgalactic
halo. No
dust continuum is detected at rest-frame ~160 micron, setting an upper limit on the infrared luminosity of L_IR < 1.4 x 10^11 Lsun, overall consistent with expectations from rest-frame UV to near-infrared SED modeling under energy balance. Converting the
galaxy-scale [CII] emission into cold gas mass, we find log(M_mol/Msun) = 9.53 (+0.32/-0.31) and log(M_HI/Msun) = 9.46-10.34, depending on the assumed calibration and
metallicity. Despite being approximately 10x more gas-poor than typical
star-forming
galaxies at fixed
redshift,
stellar mass, and [CII] to gas mass conversion, RUBIES-UDS-QG-z7 retains a substantial cold gas reservoir with fractions f_gas >~ 20% and long depletion timescales across most assumptions. The extended [CII]
halo carries approximately twice as much gas as the
galaxy alone and shows a blueshifted velocity offset consistent with the tentative gas
outflow detected in MgII absorption in previous work, suggesting a past episode of AGN-driven gas expulsion possibly linked to the suppression of
star formation. The presence of a large gas reservoir in and around a massive quiescent
galaxy just 700 Myr after the Big Bang implies that whatever mechanism is suppressing
star formation must be remarkably effective at maintaining a low
star formation efficiency on ~100 Myr timescales, even in the presence of abundant fuel.
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All authors F. Valentino, A. Pensabene, A. Weibel, A. de Graaff, D. J. Setton, P. Oesch, G. Brammer, W. M. Baker, R. Bezanson, J. E. Greene, K. E. Heintz, K. Ito, M. Lee, J. Leja, J. Matthee, B. Wang, K. E. Whitaker, C. C. Williams, P. Zhu
Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det
Enhanced electron-beam lithography to reduce the frequency scatter of 200-400 GHz superconducting microstrip resonators for on-chip filterbank spectrometers
L. G. G. Olde Scholtenhuis, D. J. Thoen, J. J. A. Baselmans et al. (+4 more)
Integrated superconducting spectrometers (ISSs) provide the instantaneous bandwidth, sensitivity, and scalable architecture for large-scale spectroscopic surveys in submillimeter-wave astronomy and cosmology. However, the accuracy with which the resonant frequencies of superconducting microstrip band pass filters can be spaced, has limited the spectral resolution for these spectrometers with continuous spectral coverage to $\frac{F}{\Delta F} < 500$. The origin of this frequency scatter has been largely unknown. In this work, we demonstrate a four-fold improvement in the frequency spacing of superconducting microstrip resonators by optimizing electron-beam lithography. We find that reducing the beam step size (BSS) on the nanometer scale reduces the random frequency scatter, and that avoiding main-field stitching across filter patterns can eliminate a systematic frequency shift between groups of resonators, indicating the different origins of these two modes of frequency deviation. These findings demonstrate that nanometer-scale control of lithographic processes is imperative for the realization of the next-generation integrated superconducting spectrometers with higher spectral resolution.
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All authors L. G. G. Olde Scholtenhuis, D. J. Thoen, J. J. A. Baselmans, K. Karatsu, L. H. Martin, S. Vollebregt, A. Endo
Astrophysics of Galaxies
All-sky modeling of Galactic emission at radio and microwave frequencies
Gabriel A. Hoerning, Clive Dickinson, Stuart E. Harper et al. (+13 more)
We present a new all-sky model of low-frequency diffuse
Galactic emission in the regime where synchrotron, free-free, and spinning
dust dominate. The model extends the Planck 2015 diffuse component-separation analysis by incorporating recent
radio and microwave surveys. We fit 35 full- and partial-sky maps at 1 degree resolution, including S-PASS at 2.30 GHz, C-BASS at 4.76 GHz, and QUIJOTE at 10-20 GHz, together with reprocessed WMAP and Planck LFI data from the Cosmoglobe collaboration and Planck HFI channels. Using a
Bayesian parametric approach with Commander, we derive spatially varying amplitude and spectral parameter maps for the dominant low-frequency foreground components in total intensity. The main products are a full-sky synchrotron amplitude and spectral-index solution, an all-sky characterization of spinning
dust emission with a single-component log-normal spectral model, and a reconstructed all-sky total-intensity map at 4.76 GHz tracing diffuse synchrotron emission with reduced systematics relative to Haslam 408 MHz. The revised low-frequency anchoring increases the recovered synchrotron amplitude: at 4.76 GHz, it is approximately a factor of two higher than the Planck 2015 prediction. The model achieves RMS temperature residuals below 10 $\mathrm{\mu}$K over 95% of the sky up to 353 GHz, with fractional residuals below 1.5% in the
Galactic plane and below 5% across QUIJOTE bands. Residual angular power spectra lie more than two orders of magnitude below the CMB spectrum. These products describe the transition between
radio and microwave emission and provide a new reference for foreground modeling and sky-simulation applications.
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All authors Gabriel A. Hoerning, Clive Dickinson, Stuart E. Harper, Roke Cepeda-Arroita, Hans K. Eriksen, Melis O. Irfan, J. Patrick Leahy, Jamie Leech, Michael E. Jones, Timothy J. Pearson, Michael W. Peel, Vasundhara Shaw, Angela C. Taylor, Duncan J. Watts, Ingunn K. Wehus, Gilles Weymann-Despres
Astrophysics of Galaxies · Cross-listed from cond-mat.stat-mech
From Landau Equation and Large Deviations to Efficient Simulations of Dynamical Fluctuations
Anwar El Rhirhayi, Jean-Baptiste Fouvry and Julien Barré
The (deterministic) Landau equation captures the mean long-term
evolution of dynamically hot long-range interacting finite-$N$ systems. Though successful, this kinetic equation fundamentally ignores dynamical fluctuations. Building upon Large Deviation Theory, we present a physically-consistent system of Langevin equations that simultaneously recovers the mean Landau dynamics and accurately captures the corresponding fluctuations among different realizations. We show in particular how these Langevin equations can be derived from Rostoker's principle in the limit of weak two-body deflections. We extensively validate these equations against tailored direct $N$-body simulations, showing an exquisite level of agreement.
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High Energy Astrophysical Phenomena
A broadband view of the thermal and non-thermal emission from the embedded massive star cluster RCW 38
Giada Peron, Andrea Bracco, Giovanni Morlino et al. (+4 more)
Gamma-ray emission has now been detected from a variety of source classes in the
Galaxy, including clusters of young massive
stars. RCW 38, a very young embedded massive
star cluster, is a case of particular interest: its gamma-ray emission detected up to hundreds of GeV, provided the first observational evidence of high-energy particle acceleration powered exclusively by
stellar winds. In this work, we aim to characterize the emission mechanisms responsible for the gamma-ray flux in RCW 38 and to provide estimates of the acceleration efficiency, as well as the fraction of accelerated electrons compared to
protons, $K_{ep}$. We present the most comprehensive multi-wavelength study of a single
star cluster to date. Our analysis ranges from MHz
radio observations obtained with the GLEAM-X survey from the Murchison Widefield Array (MWA) to GeV gamma-ray data from
Fermi-LAT, and includes GHz and THz measurements from Parkes, Planck, and IRAS. We model the thermal and non-thermal emission of RCW 38 using an eight-parameter model constrained by the Markov chain Monte Carlo method. Our results support an interpretation in which the gamma-ray emission from RCW 38 is produced by hadronic interactions with the host molecular cloud. We derive robust constraints on the electron-to-
proton ratio, with $K_{ep} \lesssim 10^{-3}$, and on the acceleration efficiency, estimated to be $\gtrsim$1%, consistent with the values required to explain the
cosmic-ray composition, and in particular its $^{22}$Ne anomaly. These results strengthen the idea that
stellar clusters play a significant role as contributors to
cosmic-ray
protons in our
Galaxy at least up to energies of a few TeV. Future investigations with the next generation of ground-based detectors will determine whether they also play a relevant role at higher energies, particularly in the context of the
cosmic-ray knee.
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All authors Giada Peron, Andrea Bracco, Giovanni Morlino, Silvia Mantovanini, Elena Amato, Daniele Galli, Marco Padovani
Instrumentation and Methods for Astrophysics
High multiplex and precision: the design and development of FLEX, a grid-based fiber positioner with large patrol radius and minimized telecentric error
Aaron Omadutt, Roelof S. de Jong, Will Saunders et al. (+5 more)
In next-generation spectroscopic facilities, high-multiplex fiber positioning systems must operate within highly constrained focal surfaces, such as the Wide-Field Spectroscopic
Telescope (WST) requiring 30,000+ fibers across a 1.4-meter surface. The Fiber Location EXtender (FLEX) positioner meets these constraints by improving fiber patrol radii while minimizing telecentric error and positioner spacing for dense clustering and high Multi-Object Spectrograph (MOS) multiplexing. The patented FLEX concept utilizes a superelastic nickel-titanium
alloy (Nitinol) inside three concentric, geometrically altered tubes. This construction ensures the tip remains parallel with its base during tilting, while internal routing allows the fiber to run freely along the axis to minimize Focal Ratio Degradation (FRD). Designed for a patrol radius of 2.5x the pitch within the WST architecture, the design delivers a maximum patrol radius up to ~22.5 mm with a telecentric error of less than 0.39 degrees. FLEX utilizes three piezoelectric actuators to provide large radial displacements and precise focus adjustment. To scale this architecture, a modular focal surface layout of 90 identical curvilinear modules has been devised. This layout houses 30,240 positioners across a 2-degree hexagonal field-of-view (FoV), accommodating a central hole for an Integral Field pickoff mirror. Only three support struts are required, obscuring just 0.8% of the FoV while allowing full positioner coverage. One in 16 positioners is allocated for high-resolution spectroscopy, with the remainder split among three low-resolution spectrograph sets; all four sets achieve virtually full coverage of the FoV.
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All authors Aaron Omadutt, Roelof S. de Jong, Will Saunders, Joseph W. Barrow, Suryansh Saxena, Jon Lawrence, Thomas Liebner, Frank Dionies
High Energy Astrophysical Phenomena
Probing dipole and quadrupole anisotropy in Gamma-ray bursts from Swift dataset
Vedant Mokal and Shantanu Desai
Testing the validity of the cosmological principle's assumption of large-scale isotropy remains crucial for modern cosmology. We investigate the angular distributions of gamma-ray bursts using the GRB catalog from Neil Gehrels Swift Observatory (Swift) for an independent probe of isotropy. Using the HEALPix spherical harmonic decomposition, we estimate the dipole and quadrupole amplitudes and compare them against the null hypothesis obtained from 500 isotropic Monte Carlo realizations. Our results show 2.9$\sigma$ dipole and 7.2$\sigma$ quadrupole amplitude when applied to the raw data. To account for observational biases, we then create an exposure map using the pointing history, roll angle, and the partial coding fraction of the Swift
Telescope. Reevaluating the null hypothesis using this map reduces the significance of these anisotropies to less than $1\sigma$. Therefore, our findings confirm statistical isotropy of the GRB sky using the Swift data, consistent with previous studies. We have also made the Swift exposure map publicly available.
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High Energy Astrophysical Phenomena
XRISM Time-resolved Fe K$\alpha$ Spectroscopy of NGC 4395: Time-variable Inner-disk Emission
Taiki Kawamuro, Satoshi Yamada, Hirofumi Noda et al. (+3 more)
We report the first XRISM observation of the low-mass AGN in the nearby
dwarf galaxy NGC 4395 ($M_{\rm BH}\sim10^{4-5}\,M_\odot$), complemented by a simultaneous NuSTAR observation. We constrained the continuum by jointly fitting the XRISM/Resolve (2-12 keV) and NuSTAR (3-30 keV) spectra while excluding the Fe K band (5.5-7.5 keV). Relative to this baseline continuum, the time-averaged Resolve spectrum revealed an unresolved neutral Fe K$\alpha$ core with a velocity width of $\lesssim$110 km s$^{-1}$ and an adjacent redward wing. The red wing was well reproduced by an additional relativistically broadened Fe K component. Furthermore, time-resolved spectroscopy with $\approx$87 ks bins showed that the diskline profile varied significantly over the $\sim$400 ks observation. This
evolution can be interpreted in terms of changes in the inner radius of the line-emitting region, together with a possible inclination modulation with a period of $\approx$210 ks. If interpreted as Lense-Thirring precession of a tilted inner flow, the observed period would favor the low end of the black hole mass estimates ($M_{\rm BH}\approx9\times10^3\,M_\odot$) and imply a moderate
spin ($a\gtrsim0.6$). These results highlight the capability of XRISM to track relativistic disk dynamics in AGNs.
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All authors Taiki Kawamuro, Satoshi Yamada, Hirofumi Noda, Yoshiyuki Inoue, Shoji Ogawa, Misaki Mizumoto
Astrophysics of Galaxies
Star Formation at the Periphery of a Molecular Superbubble: The Case of G12.79+0.43
Arun Seshadri, Veena V. S., Sarita Vig et al. (+1 more)
We present a multiwavelength investigation of the molecular cloud complex G12.79+0.43, which extends over $\sim18'$ on the sky. Several infrared- and
radio-bright regions are arranged along an irregular rim, surrounding a central region characterised by diffuse 24~$\mu$m emission. CO molecular line observations reveal three prominent velocity components along the line of sight. Low-frequency
radio continuum observations at 666 and 1300~MHz show diffuse emission spanning $\sim10.5'$ ($\sim$7.3~pc), predominantly filling the central region enclosed by the infrared-bright structures. We identify 70 compact
radio sources and six \hii~regions across the cloud complex, which are likely powered by early B-type ZAMS
stars. Using infrared data, we identify a total of 82 YSO candidates, including 28 Class~I sources, distributed across the cloud complex. On larger scales, the kinematics of the molecular gas over a $2^\circ\times2^\circ$ field indicate that G12.79+0.43 is located along the rim of a larger molecular superbubble (diameter $\sim50$~pc) that also encompasses the well-known W33 region. The inferred expansion age of this superbubble is $\sim0.3$~Myr. While the spatial association between G12.79+0.43 and the superbubble is evident, the current data do not allow us to establish a clear causal connection between the superbubble
evolution and the ongoing
star formation within G12.79+0.43.
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All authors Arun Seshadri, Veena V. S., Sarita Vig, Ashish P John
Cosmology and Nongalactic Astrophysics
Accurate Galaxy Cluster Shear and Mass Calibration for LSST with AnaCal
Conghao Zhou, Xiangchong Li, Hao-Yi Wu et al. (+12 more)
The observed abundance of
galaxy clusters as a function of mass and
redshift provides a powerful route to precision cosmology; a key challenge for cluster cosmology is to establish the relation between cluster observables and cluster masses, for which cluster weak gravitational
lensing has become the standard tool. A key challenge for cluster
lensing is that the shear signal near cluster centers can reach the non-linear regime, where many shear
estimators rely on perturbative assumptions that must be explicitly validated. In this work, we use image simulations to test the performance of the shear
estimator AnaCal for cluster weak
lensing under conditions representative of the 10-year LSST data. We find that AnaCal recovers the input shear with minimal bias even at mildly high shear, $|g|\sim 0.15$. We discover a radially decreasing mean shear response as seen previously in data, driven by the radial dependence of the convergence field; if unmodeled, this effect can bias shear inference. We also find a positive shear-estimation bias at third order in the reduced shear near the cluster center. However, because only a small fraction of
galaxies lie in the high-shear regime and those measurements are further downweighted by the covariance
matrix, the resulting mean cluster-mass bias for cluster lens masses in $[10^{14} M_\odot, 10^{15} M_\odot]$ – adopting a scale cut of $\sim 0.2$ Mpc at $z=0.25$ – is $0.24 \pm 0.26\%$ under ideal settings. These results demonstrate that AnaCal is a robust tool for accurate cluster mass calibration in the LSST era.
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All authors Conghao Zhou, Xiangchong Li, Hao-Yi Wu, Anja von der Linden, Tesla Jeltema, Tae-hyeon Shin, Simon Birrer, Tomomi Sunayama, Shenming Fu, Prakruth Adari, Lucie Baumont, Surhud More, Anthony Englert, Miranda Gorsuch, Andrés A. Plazas Malagón
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Reconstructing the slope of a nearly flat quintessence potential from cosmography
Saikat Chakraborty, Peter K.S. Dunsby and Robert J. Scherrer
We revisit thawing quintessence models with nearly flat scalar-field potentials using a cosmographic framework. Earlier work indicates that the cosmographic reconstruction of the slope $\lambda=-(dV/d\phi)/V$ of the quintessence potential in the general case requires the knowledge of the cosmographic paremeters up to the jerk parameter $j$. In this work we show that the slow-roll conditions $[(dV/d\phi)/V]^2 \ll 1$ and $|(d^2V/d\phi^2)/V| \ll 1$ allow the reconstruction of the slope of a nearly flat potential with knowledge of only the deceleration parameter $q$ (and the density parameter $\Omega_\phi$). Confronting the assumption of near-flatness with the cosmographic data after DESI DR2, however, reveals possible tension between the two. We further show that these models exhibit attractor behaviour in the $w$–$\Omega_\phi$ and $w$–$w'$ phase planes, corresponding to a universal thawing
evolution with $w \approx -1$ at early times. We also derive the corresponding relation in the cosmographic $q$–$j$ plane and show that different cosmological expansion histories can produce the same thawing
evolution. Nevertheless, all viable trajectories remain close to the $\Lambda$CDM limit $j=1$.
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Astrophysics of Galaxies
VST-SMASH: VST Survey of Mass Assembly and Structural Hierarchy II. Exploring dwarf galaxies in the vicinity of NGC 5068 and of the two galaxies NGC 5084 and NGC 5087 at the edges of the Virgo Supercluster
C. Tortora, R. Ragusa, L. K. Hunt et al. (+9 more)
We present a study of
dwarf galaxy candidates in the deepest optical imaging yet obtained of the field surrounding the nearby
galaxies NGC 5068 and NGC 5084/NGC 5087, the latter two located in the peripheries of the Virgo Supercluster. This field, covering $\sim 2.6$ deg$^2$, was observed as part of the multi-band, wide-field and very deep data from VST-SMASH, a distance-limited program ($D < 11$ Mpc) that reaches $g$- and $r$-band surface brightness depths of $\mu \sim 30$ mag arcsec$^{-2}$. Using a two-step visual inspection procedure, we identify 47
dwarf galaxy candidates and perform the surface photometry of the sample and the fitting procedure with 1D Sérsic model on their profiles. Only 4
galaxies were previously reported in the literature, augmenting by one order of magnitude the number of
dwarfs discovered in these regions. The colors (median $g-r = 0.57$ and $r-i = 0.24$ mag) and structural properties of the
dwarf candidates are consistent with the literature, as are their scaling relations with effective radius, Sérsic index ($n < 2$), and absolute magnitude. We also investigate their central colour gradients, which exhibit significant scatter, and discuss them within the broader context of
galaxy formation. We finally analyze their spatial distribution relative to potential host
galaxies. We identify reasonable associations with NGC 5084, NGC 5087, and NGC 5068 as likely hosts for a significant fraction of the sample. Several candidates are at physically credible distances from NGC~5068, despite what their offset size-luminosity relation alone might indicate. Future spectroscopic and deeper imaging follow-up is required to determine distances and velocities, enabling robust association with hosts, studies of satellite distributions and counts, and comparisons with cosmological expectations for planes of satellites and dark matter models. (abridged)
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All authors C. Tortora, R. Ragusa, L. K. Hunt, A. Unni, M. Baes, Abdurro'uf, F. Annibali, M. Gatto, N. R. Napolitano, H. Su, A. Venhola, D. Carollo
Instrumentation and Methods for Astrophysics
Optimization and robustness of cost-efficient seismic arrays for Newtonian noise cancellation at the Einstein Telescope
Patrick Schillings and Johannes Erdmann
Newtonian noise is expected to be the dominating noise source for low frequencies at the Einstein
Telescope. It originates from seismic waves that cause density fluctuations in the rock around the interferometer. The mitigation strategy for Newtonian noise relies on an array of seismometers, placed at depth in boreholes, which provides measurements of the seismic wave field. We optimize the positions of the individual seismometers for the mitigation capabilities of the array for a full corner of the Einstein
Telescope. We find that the mitigation capabilities of arrays with multiple seismometers in each borehole match the capabilities of only somewhat smaller arrays but with only one seismometer per borehole. Mitigation is further improved by extending the array with seismometers in the interferometer tunnels. Such configurations may hence provide a cost-effective way towards realizing an efficient seismic array. In each case, we quantify the broadband mitigation performance in the range from 1 to 10 Hz for arrays that are optimized for a frequency of 10 Hz, as well as the robustness of the arrays with respect to variations from their optimized positions. We find that larger arrays with several seismometers per borehole and additional seismometers in the tunnels provide promising broadband performance above 3 to 4 Hz and that such arrays are particularly stable against variations in the seismometer positions with mitigation factors $>6$ for an array of 20 boreholes with 3 seismometers each and $>15$ for a large array of 50 boreholes with 10 seismometers.
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High Energy Astrophysical Phenomena
Little Red Dots as Supermassive Counterparts of SS 433: A Hyper-Eddington Accretion Framework
Shuying Zhou, Mouyuan Sun, Xihan Ji et al. (+11 more)
High-
redshift little red dots (LRDs) are compact sources characterized by V-shaped spectral energy distributions (SEDs), broad emission lines, and often prominent Balmer breaks. Their high number density and apparently large black hole masses suggest that they are essential to the early
evolution of
galaxies and supermassive black holes (SMBHs); however, the nature of their central engines remains uncertain. Here, we propose that LRDs are the supermassive, high-
redshift counterparts of the hyper-Eddington accreting
Galactic microquasar SS~433, viewed at high inclinations. By scaling the hyper-Eddington
accretion physics from
stellar-mass black holes to supermassive scales, we show that the observed LRD features, including X-ray weakness, soft optical SEDs, apparent sub-Eddington
accretion ratio, and Balmer breaks, emerge naturally from the self-shielding geometry of a puffed-up
accretion disk. In this framework, the broad-line regions are ionized by anisotropic radiation escaping from the inner disk, analogous to the unseen UV/X-ray emission revealed by the W50 nebula in SS 433. Their low-inclination or lower-
accretion-rate counterparts would appear as little blue dots (LBDs) or normal active
galactic nuclei. Our model predicts that the Balmer break strength positively correlates with the broad-line width, that the emission lines are more variable than the optical continuum, that LRDs are intrinsically more luminous than observed, and that LBDs are more variable than LRDs. This unified-scale model redefines LRDs as the essential laboratories for observing the rapid
accretion-driven growth that shaped the early assembly of
galaxies and their central SMBHs.
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All authors Shuying Zhou, Mouyuan Sun, Xihan Ji, Ya-Ping Li, Luis C. Ho, Roberto Maiolino, Zhen-Yi Cai, Hai-Cheng Feng, Manqi Fu, Wei-Min Gu, Tong Liu, Junfeng Wang, Jianfeng Wu, Yongquan Xue
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Population-level correlations in Bayesian statistics: an illustrative model for gravitational-wave astronomy
Caroline B. Owen, Alexandre Toubiana and Davide Gerosa
With increasingly large numbers of gravitational-wave events, population inference is now beginning to move beyond predictions of marginal distributions and to probe correlations between compact-binary parameters such as masses,
spins, and
redshifts. These correlations have strong constraining power for both astrophysics and tests of general relativity. In this paper, we present an idealized analytical model to study the interplay between single-event correlations, systematic biases, and population-level correlations. With this, we investigate the potential emergence of false-positive measurements of population-level correlations. We quantify how the presence of correlations at the single-event level between a pair of parameters increases the uncertainty of population-level correlations for those parameters, potentially obscuring the true underlying population correlation if present. We also find that if waveform systematics lead to biases that are correlated across the catalog (which is likely, because certain regions of the parameter space are more difficult to model), this can be effectively absorbed by a population analysis that targets correlations and can be misinterpreted as such. This simple Gaussian-based model may serve as a broad compass for future, more detailed explorations.
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Instrumentation and Methods for Astrophysics
Quality Assessment of Spectroscopic Data Reduction Pipelines Using Artificial Intelligence: Scrutinizing Data Release 2 from the DESI Survey
V. Torres-Gomez, J. Suarez-Perez, J. E. Forero-Romero et al. (+45 more)
Large spectroscopic surveys now collect data at a scale that makes traditional visual inspection impractical. We present an unsupervised pipeline for spectroscopic quality assessment that requires no labeled training data. The method combines Uniform
Manifold Approximation and Projection for dimensionality reduction with Friends-of-Friends clustering to isolate anomalous spectra for targeted review. We apply this pipeline to 58,291,334 spectra across 14,199 tiles from DESI Data Release 2, processing each tile independently to produce a tile-level outlier catalog. In each tile, the pipeline separates a dense core of typical spectra from small, isolated components and singletons, yielding a total of 1,095,816 outlier candidates. The mean tile-level outlier fraction is about 1.96 percent overall, with values of 0.76 percent and 2.36 percent for the dark and bright main-survey programs, respectively. From the visual inspection of 391 outlier candidates from the dark and bright programs of the main survey, we find that 66.8 percent exhibit identifiable spectral anomalies consistent with known reduction and calibration effects. By contrast, only 4.1 percent carry a non-zero quality flag from the standard reduction pipeline. This shows that the method provides a complementary quality-assessment layer to existing pipeline diagnostics and recovers a substantial population of problematic spectra that standard diagnostics miss. Extrapolating to the main-survey catalog, we estimate that approximately 218,000 candidate outliers are free of identifiable reduction artifacts and may correspond to genuine atypical spectra in the context of DESI. The pipeline is scalable, reproducible, and directly comparable across successive data releases, making it a practical quality-assurance monitor for DESI and future multi-object spectroscopic surveys.
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All authors V. Torres-Gomez, J. Suarez-Perez, J. E. Forero-Romero, S. Bailey, A. Kremin, B. Dey, R. P. Nathan, S. Panda, J. Aguilar, S. Ahlen, D. Bianchi, D. Brooks, T. Claybaugh, A. de la Macorra, P. Doel, S. Ferraro, A. Font-Ribera, E. Gaztanaga, S. Gontcho A Gontcho, G. Gutierrez, K. Honscheid, C. Howlett, R. Joyce, S. Juneau, D. Kirkby, O. Lahav, M. Landriau, L. Le Guillou, M. E. Levi, M. Manera, A. Meisner, R. Miquel, J. Moustakas, S. Nadathur, N. Palanque-Delabrouille, W. J. Percival, F. Prada, I. Perez-Rafols, G. Rossi, L. Samushia, E. Sanchez, D. Schlegel, H. Seo, R. Sharples, J. Silber, G. Tarle, B. A. Weaver, H. Zou
Instrumentation and Methods for Astrophysics
Classification of Eclipsing Binary Light Curves in Gaia DR3: A Machine Learning Approach
Bedri Keskin and Özgür Baştürk
Gaia Data Release 3 (DR3) presents a unique
dataset with approximately 2.1 million eclipsing binary
star candidates. The unsustainability of manually classifying such a large volume of data has necessitated the development of reliable and scalable automated techniques. In this study, a novel
multimodal deep learning model has been developed for the automated classification of approximately 2 million eclipsing binary
stars in the
Gaia DR3 archive based on their light curve morphologies (EA, EB, EW). The developed architecture simultaneously utilizes a Convolutional Neural Network (CNN) that extracts visual features from light curve images and a Multilayer Perceptron (MLP) that processes
geometric model parameters. Noise-free synthetic light curves were used during the training process to ensure the model focuses on
geometric shapes. Tests showed that the model achieved an accuracy rate of over 95% for all classes, exhibiting excellent separation performance, particularly in EA-type systems. As a result of the automated classification performed with the trained model, 40% of the
Gaia DR3 eclipsing binaries were classified as EA, 30% as EB, and 30% as EW. This study provides a highly accurate and transferable classification framework for future large-scale sky surveys.
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Astrophysics of Galaxies
Clumpy Disk, Interloper, or Merger? Nature of a Distant Galaxy Pair at 5 kpc Projected Separation
Hajar Aziz, Vivian U, Archana Aravindan et al. (+8 more)
We present the morphological, photometric, and spectroscopic properties of a z ~ 1
galaxy, "lil gal", serendipitously detected in JWST Mid Infrared Instrument (MIRI) images of nearby
galaxy VV 340. In the MIRI F560W and F770W images, we identify what appears to be a spiral
galaxy with a central bulge. However, in the F1500W image, a second peak appears ~0.7" northwest (NW) from the central bulge, calling into question the nature of this source as a clumpy disk, a high-
redshift interloper, or a
galaxy merger. Multi-band analyses of the three MIRI and four Hubble Space
Telescope (HST) images suggest a photometric
redshift of ~0.92. Spectroscopic analyses of data from the Keck Near-Infrared Echellette Spectrometer (NIRES) reveal two sets of [N II] and H-alpha emission lines corresponding to the two observed sources. A
redshift of z = 0.9248 is identified for the NW companion. Fainter emission lines are identified from the underlying
galaxy at z = 0.9225, suggesting a merging
galaxy pair at a projected separation of ~5 kpc. From the emission line ratios from Keck NIRES and Keck
Cosmic Web Imager (KCWI) spectra, we classify the system as hosting regions of active
star formation, likely attributed to merger-induced starburst activity. The results demonstrate the necessity of resolved, spectroscopic follow-up analyses of
galaxies found in deep JWST images to disentangle the role of
galaxy mergers from clumpy disk
galaxies at z ~ 1 to
cosmic noon and beyond.
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All authors Hajar Aziz, Vivian U, Archana Aravindan, Raymond P. Remigio, Gabriela Canalizo, Justin A. Kader, Marina Bianchin, Yiqing Song, Tianmu Gao, Jeff Rich, Rosalie McGurk