Astrophysics of Galaxies
Detailed Analysis of the NGC 2168 Cluster, Leveraging Gaia DR3
Nasser M. Ahmed, Remziye Canbay and Deniz Cennet Ç{\i}nar
NGC 2168 (M35) serves as a fundamental
benchmark for studying
stellar evolution and dynamical environments at the transition between young and intermediate-age populations. We present a comprehensive analysis of the cluster's kinematic, structural, and astrophysical properties utilizing high-precision astrometry and photometry data from
Gaia Data Release 3 (DR3), complemented by 2MASS data. A statistical membership assessment yields a clean sample of probable members (N ~ 1397), with mean proper motion components of mu_alpha cos(delta) = 2.278 +/- 0.006 mas/yr and mu_delta = -2.893 +/- 0.006 mas/yr, along with a mean trigonometric parallax of varpi = 1.154 +/- 0.052 mas. We derived the cluster's fundamental parameters via isochrone fitting, determining an age of 190 +/- 12 Myr, a
metallicity of [M/H] = -0.048 dex, and a probabilistic distance of 840 +/- 54 pc. The radial density profile is well described by a generalized King model with beta = 1 (rc = 7.97', rcl = 36.69'), revealing the presence of a loosely bound, extended
stellar halo. Furthermore, we detect a spatial elongation oriented perpendicular to the
Galactic plane, likely a signature of vertical
tidal heating or disk shocking. The mass function analysis exhibits a
multimodal Gaussian structure, suggesting a complex dynamical formation history beyond a simple power-law distribution. Finally, orbital integration confirms NGC 2168 as a thin disk object with a maximum vertical excursion of ~171 pc, consistent with the observed vertical morphological deformation.
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Earth and Planetary Astrophysics
Unified Formation Channel of Hot and Warm Jupiters via Planet-Planet Scattering
Julia Esposito, Gongjie Li and Songhu Wang
Recent observations show distinct orbital architectures for hot and warm Jupiters: hot Jupiters span a wide range of
stellar obliquities and tend to host distant companions without close-by companions, whereas warm Jupiters are often aligned and accompanied by both close-by and distant companions. In this paper, we revisit
planet-
planet scattering and demonstrate that it provides a unified framework for both populations. Using N-body simulations with tides, we explore three regimes: hot (a_1 < 0.1 AU), warm (0.1 < a_1 < 1 AU), and cold (1 < a_1 < 10 AU) scattering. Hot scattering predominantly produces compact hot-Jupiter pairs, which are rarely observed, implying this channel is rare. Cold scattering readily produces retrograde hot Jupiters and likely constitutes a main reservoir feeding the hot-Jupiter population. However, cold scattering produces few inner warm Jupiters at a at about 0.1-0.3 AU. We show that warm scattering naturally fills this gap: high-inclination inner warm Jupiters produced by warm scattering are preferentially removed through further eccentricity excitation followed by
tidal circularization into hot Jupiters. As a result, the surviving inner warm Jupiters are biased toward a broad range of eccentricities but modest inclinations, producing the observed "eccentric-but-aligned" population. This story makes testable predictions: (i) warm Jupiters, especially at a >~ 0.3 AU, should not be exclusively aligned, and (ii) warm Jupiters should often host nearby companions with non-negligible mutual inclinations up to <~ 30 degrees.
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Cosmology and Nongalactic Astrophysics
Phantom-Crossing Dark Energy and the $\Omega_m$ Tug-of-War
David Shlivko and Vivian Poulin
Recent analyses combining data from the
cosmic microwave background (CMB),
baryon acoustic oscillations (BAO), and Type Ia
supernovae (SN) have revealed a tentative observational preference for phantom crossing in the dark energy equation of state $w$. We argue that this preference is a natural consequence of the $\Omega_m$ tensions that arise when these
datasets are individually fit to $\Lambda$CDM, specifically because of the ordering $\Omega_m^\mathrm{BAO} < \Omega_m^\mathrm{CMB} < \Omega_m^\mathrm{SN}$. We show both theoretically and empirically that models with phantom crossing can shift all of these inferred $\Omega_m$ values toward mutual
alignment. In contrast, quintessence theories restricted to $w \geq -1$ can alleviate the tensions with SN data but only at the cost of exacerbating the BAO-CMB discrepancy. We therefore conclude that it is the BAO and CMB measurements - not the SN data - that drive the preference for phantom crossing over quintessence in joint analyses. Moreover, we point out that SN data exhibit greater tensions with the other
datasets when fit to phantom-crossing models than when fit to quintessence, causing the preference for phantom crossing to be weaker in joint CMB+BAO+SN analyses than in analyses of CMB+BAO data alone.
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Astrophysics of Galaxies
Reinterpreting the puzzling properties of z>6 galaxies within a variable IMF framework
Fabio Fontanot, Gabriella De Lucia, Lizhi Xie et al. (+6 more)
Recent results form the James Webb Space
Telescope (JWST) report space densities for bright and massive
galaxies at z>7 that far exceed expectations of theoretical models of
galaxy formation, prompting a revision of our understanding of the physical processes leading to the assembly of the first luminous structures. In this work we present predictions from a realization of the
GAlaxy Evolution and Assembly (GAEA) model, which implements a prescription for a variable
stellar initial mass function (IMF). This prescription is inspired by high-resolution numerical simulations that account for the role of
cosmic rays (CR) as regulators of the
star formation rate (SFR) in
giant molecular clouds. In our approach, SFR density is assumed to be a proxy for the CR density, providing a link between the IMF shape and the predicted physical conditions of the
star forming interstellar medium. Our results show that, in our model framework, assuming such a variable IMF reproduces several properties of the z>6
galaxy population, with no further modification of the feedback model, including their UV luminosity functions up to z~13. In order to compare model predictions with available estimates for the
galaxy stellar mass function (GSMF), we reconstruct
stellar masses from the model's synthetic photometry assuming a universal IMF, reflecting standard observational practice. Under this approach, we show that the model can reproduce the
evolution of the GSMF up to the highest
redshifts accessible. Our findings highlight the need to consider a variable IMF shape in the error budget associated with
stellar mass estimates. We show that the
evolution of both the slope and normalization of the gas-phase mass
metallicity relation can be used as powerful discriminant between models of early
galaxy formation assuming different IMF
evolution.
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All authors Fabio Fontanot, Gabriella De Lucia, Lizhi Xie, Stefano Zibetti, Francesco La Barbera, Sebastiano Cantarella, Michaela Hirschmann, Stephane Charlot, Gustavo Bruzual
High Energy Astrophysical Phenomena
Where within the 3C 84 jet are $\gamma$-rays produced?
Georgios F. Paraschos, Ioannis Liodakis, Svetlana Jorstad et al. (+49 more)
The location of $\gamma$-ray creation and emission within extra-
galactic jets is a matter of active debate. One particularly well-suited source to pinpoint the location is the nearby, bright
radio galaxy 3C 84, harbouring a powerful jet. Here we investigate the origin of $\gamma$-rays measured during a recent $\gamma$-ray
flare, by analysing the linear polarisation signal of close-in-time very long baseline interferometry (VLBI) observations at centimetre and millimetre wavelengths. While 3C 84 is overall almost unpolarised, we find that close-in-time to the $\gamma$-ray
flare peak regions at parsec-scale distances from the central engine shows a fractional linear polarisation increase. Under the physically well-motivated assumption of a causal relation between this polarisation enhancement and the $\gamma$-ray
flare, and combined with insights from concurrent X-ray polarisation measurements, the $\gamma$-rays being created in this region is a physically motivated scenario, in a process consistent with synchrotron self-Compton.
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All authors Georgios F. Paraschos, Ioannis Liodakis, Svetlana Jorstad, Yuri Y. Kovalev, Sudip Chakraborty, Frederic Marin, Steven R. Ehlert, Efthalia Traianou, Lena C. Debbrecht, Ivan Agudo, Thibault Barnouin, Jacob J. Casey, Laura Di Gesu, Philip Kaaret, Dawoon E. Kim, Fabian Kislat, Ajay Ratheesh, M. Lynne Saade, Francesco Tombesi, Alan Marscher, Jose-Luis Gomez, Alexander B. Pushkarev, Tuomas Savolainen, Ioannis Myserlis, Mark Gurwell, Garrett Keating, Ramprasad Rao, Sincheol Kang, Sang-Sung Lee, Sanghyun Kim, Whee Yeon Cheong, Hyeon-Woo Jeong, Chanwoo Song, Shan Li, Myeong-Seok Nam, Diego Alvarez-Ortega, Carolina Casadio, Chien-Ting Chen, Enrico Costa, Eugene Churazov, Riccardo Ferrazzoli, Giorgio Galanti, Ildar Khabibullin, Stephen L. O'Dell, Luigi Pacciani, Marco Roncadelli, Oliver J. Roberts, Paolo Soffitta, Douglas A. Swartz, Fabrizio Tavecchio, Martin C. Weisskopf, Irina Zhuravleva
Cosmology and Nongalactic Astrophysics
Second Order Closures for the Radiative Transfer Equation: Some Are Unstable
Nickolay Y. Gnedin and Harley Katz
The largest existing simulations of
cosmic reionization model radiative transfer with moment methods that require a closure relation. The two most commonly used closure relations are M1 and OTVET; both close the moment hierarchy at the first moment. We explore the properties of a higher, second-order closure. We show that direct generalizations of M1 and OTVET to one higher order are physically unstable - i.e., the closure equations themselves result in unstable solutions, not just their numerical implementation. In fact, a generalization of OTVET to any order higher than the first one is unstable. We are also able to show that any local (i.e., depending only on the local moments of the radiation field, like M1) second-order closure that depends only on the radiation intensity and radiation flux, but does not explicitly depend on the radiation pressure, is physically unstable. This result restricts the choice of possible second-order closure relations.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Stable black hole solutions with cosmological hair
Laurens Smulders and Johannes Noller
Dynamical dark energy theories generically introduce a time-dependent field that causes the accelerated expansion of the Universe on large scales. When
embedding black hole solutions in such a cosmological spacetime, this time dependence naturally gives rise to cosmological hair, i.e. the local black hole physics is no longer controlled by just the mass and
spin of the black hole, but also impacted by the dark energy field. However, known such solutions are unstable. Focusing on the cubic Galileon as a concrete and illustrative example, we discuss the restrictions imposed on physical solutions by their regularity and stability in detail. We explicitly derive solutions that both recover the desired cosmological long-range behaviour and give rise to well-behaved, regular and stable, short-range dynamics around black holes. We show how the nature of the scalar hair around these local black hole solutions encodes cosmological information, highlighting novel and tantalising prospects of directly probing cosmological dynamics with black hole observations.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Slow-down of expanding bubbles in the early Universe
Nabeen Bhusal, Simone Blasi, Thomas Konstandin et al. (+2 more)
We study slow-down effects for bubbles formed in a cosmological first-order phase transition (PT) focusing on deflagrations and hybrids, where the bubble wall is preceded by a shockwave of heated
plasma. Slow-down has been observed in multi-bubble simulations together with a suppression of gravitational wave (GW) emission, mostly for slow walls. We study the impact of the shock waves on the wall velocity around percolation, by considering steady-state single-bubble solutions and incorporating the possible heating effects by two different mechanisms. First, we investigate the slow-down experienced by a bubble expanding into an impeding shockwave, where the temperature is higher than at nucleation, and the fluid is no longer at rest. Taking into account such heating and kinematic effects, we find that the most significant slow-down occurs for the fastest walls, and thus cannot explain the suppression of the GWs observed in the simulations. However, these effects are stronger for PTs with a sizeable change in degrees of freedom unlike what is usually implemented in simulations, suggesting that the degrees of freedom can be an important additional parameter for characterizing the GW spectrum. For the second slow-down mechanism, we study heated droplets of false
vacuum that shrink towards the end of the PT. By implementing a suitable boundary condition motivated by energy conservation, we show how the droplet velocity, interpreted here as the late-time velocity of the bubble walls, can be predicted from the properties of the initial deflagration/hybrid, in remarkable agreement with numerical simulations. Droplets are found to shrink more slowly for stronger PTs and slower deflagrations, with mild dependence on the change of degrees of freedom. Such slow droplets naturally correlate with a suppression of GWs, while geometrical properties such as the shock width play an important role as well.
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All authors Nabeen Bhusal, Simone Blasi, Thomas Konstandin, Enrico Perboni, Jorinde van de Vis
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Kinetic Isocurvature Perturbation
Kyu Jung Bae, Dhong Yeon Cheong, Jinn-Ouk Gong et al. (+2 more)
We formulate a new class of
primordial perturbations called $\textit{kinetic isocurvature perturbations}$, where the mass density of dark matter is constant relative to the
photon number density while the kinetic energy of dark matter fluctuates in space. Such perturbations naturally arise in scenarios where a nonrelativistic heavy field decays into relativistic dark matter particles with a spatially modulated rate. As dark matter cools and becomes nonrelativistic, these fluctuations in kinetic energy leave large-scale density perturbations essentially unaffected and therefore evade the
Cosmic Microwave Background bounds on isocurvature perturbations, yet survive as spatial variations in the free-streaming scale, resulting in patch-by-patch variation of the matter power spectrum.
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All authors Kyu Jung Bae, Dhong Yeon Cheong, Jinn-Ouk Gong, Keisuke Harigaya, Chang Sub Shin
Astrophysics of Galaxies
MEOW: The increase in the obscured AGN fraction in mid-infrared from 0 < z < 6 with JWST MIRI
Teodora-Elena Bulichi, Gene C. K. Leung, Anna-Christina Eilers et al. (+16 more)
Obscured active
galactic nuclei (AGN) are often invoked to explain the rapid emergence of young
quasars at high
redshift and are crucial for building a complete census of AGN activity and black hole growth. The advent of the James Webb Space
Telescope (JWST) extends the discovery space for obscured AGN into the mid-infrared (mid-IR) with unprecedented precision through reprocessed
dust emission. In this work, we use deep JWST Mid-Infrared Instrument (MIRI) imaging from the MIRI Early Obscured AGN Wide Survey (MEOW), together with existing JWST Near Infrared Camera (NIRCam), spectroscopic, and Hubble Space
Telescope imaging data, to identify a previously unrecognized population of obscured AGN out to z ~ 6. Using spectral energy distribution (SED) modeling of the MIRI-detected sources, we identify 883 AGN over an area of ~ 131 arcmin2 and construct the AGN bolometric luminosity function, including both obscured and unobscured sources, across five
redshift bins. We find an excess in AGN abundance relative to UV-selected AGN luminosity functions, indicating a substantial obscured population missed by optical/UV surveys, with the inferred obscured fraction increasing with
redshift and reaching ~ 98-99% in our highest-
redshift bin, 4.5 < z < 6. We also find higher AGN abundances and obscured fractions than X-ray-based studies, consistent with a previously unrecognized population of heavily obscured, Compton-thick AGN revealed by mid-IR selection. These results suggest that a large fraction of supermassive black hole growth at early times occurs during heavily obscured phases largely inaccessible at other wavelengths.
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All authors Teodora-Elena Bulichi, Gene C. K. Leung, Anna-Christina Eilers, Pablo G. Perez-Gonzalez, Guillermo Barro, Steven L. Finkelstein, Micaela B. Bagley, Anton M. Koekemoer, Bren E. Backhaus, Mark Dickinson, Norman A. Grogin, Dale D. Kocevski, Ray A. Lucas, Fabio Pacucci, Nor Pirzkal, Elia Pizzati, Jan-Torge Schindler, Alberto Traina, Guang Yang
High Energy Astrophysical Phenomena
Shaping the diffuse X-ray sky: Structure, Variability and Visibility
Philipp Girichidis, Erika Rea, Ralf S. Klessen et al. (+5 more)
The Local Bubble (LB) is a hot, low-density cavity in the
solar neighborhood, inside which the
Solar System is currently located. The X-ray emission from such bubbles is strongly governed by the gas density, temperature, and the effects of line-of-sight column density. Yet the physical processes that control the formation and
evolution of this emission remain incompletely understood. We analyze a LB analogue identified within a magnetohydrodynamical simulation to investigate the key physical factors that shape its X-ray properties. In post-processing, we examine the spatial distribution, variability, and observational constraints of the X-ray emission. Our study reveals three main results: (1) Shortly after a
supernova (SN), the bulk of the X-ray emission arises from a small fraction of the bubble's volume, concentrated in hot regions around recent SN sites. Approximately 95% of the X-ray luminosity originates from less than 1% of the total bubble volume. During quiescent phases without recent SNe, the emission morphology changes substantially, with X-ray-bright regions becoming more volume-filling. (2) Column density effects strongly modulate the observable X-ray signal. Gas with column densities exceeding $N_\mathrm{H} \gtrsim 10^{20} \,\mathrm{cm}^{-2}$ efficiently absorbs soft X-ray
photons, limiting the depth to which observations can probe. This absorption causes a significant fraction of the sky to be obscured from external soft X-rays. Differences between active and quiescent phases further influence how much of the total bubble emission is visible from within. (3) The X-ray flux shows pronounced temporal variability on Myr timescales, with SN events producing rapid, transient luminosity enhancements, followed by steep declines due to adiabatic cooling. The total flux varies by several orders of magnitude, with SN-driven peaks fading within $10^5$ years.
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All authors Philipp Girichidis, Erika Rea, Ralf S. Klessen, Michael C. H. Yeung, Efrem Maconi, Manami Sasaki, Michael Freyberg, Juan D. Soler
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
What does it take to have $N_{\rm eff} < 3$ at CMB times?
Miguel Escudero, Maksym Ovchynnikov and Neal Weiner
The vast majority of extensions of the Standard Model affecting the number of effective relativistic
neutrino species ($N_{\rm eff}$) do so additively, namely, they enhance this quantity with some light state contributing to dark radiation. In this work, we consider precisely the opposite case: new physics scenarios that can lead to $N_{\rm eff} < 3$ that are consistent with all known cosmological, astrophysical, and laboratory data. We are motivated by three main reasons: 1) a recent measurement from ACT and SPT in combination with Planck that leads to $N_{\rm eff} = 2.81\pm0.12$, 2) by a new and powerful measurement of the
primordial helium abundance, which anchors $N_{\rm eff}$ to be very close to the Standard Model value one second after the Big Bang, 3) by the deployment of the Simons Observatory which will provide precise tests of the radiation content in the Universe and which may detect with a high significance cosmologies with $N_{\rm eff}<3$. We survey the main theoretical possibilities and find that only a few simple scenarios can consistently give $N_{\rm eff}=2.81\pm0.12$. One class consists of thermal electrophilic relics with masses $m\sim 8\!-\!13\,{\rm MeV}$. Another consists of out-of-
equilibrium particles decaying to $e^+e^-$ or $\gamma\gamma$, with a rather particular lifetime $0.05\,{\rm s}\lesssim \tau \lesssim 3\,{\rm min}$, mass $250\,{\rm MeV}\lesssim m \lesssim 600\,{\rm MeV}$, and abundance $\rho/\rho_\gamma\sim 0.1$ at decay. Thermal electrophilic particles are especially interesting because they can account for the dark matter in the Universe and can be tested in experiments such as SENSEI, DAMIC-M, and Oscura, and their portals to the visible sector at experiments such as NA64 and LDMX. We conclude that if the Simons Observatory confirms that $N_{\rm eff} \simeq 2.8$, it will point to very specific extensions of the Standard Model.
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Astrophysics of Galaxies
SDSS-V LVM: A spatially resolved study of the physical conditions and the chemical abundance discrepancy in the Lagoon Nebula (M 8)
Amrita Singh, Guillermo A. Blanc, Nimisha Kumari et al. (+19 more)
The abundance discrepancy problem refers to the systematic differences observed between chemical abundances derived from collisionally excited lines (CELs) and recombination lines (RLs) of heavy ions. It remains a major unsolved problem in the study of ionized nebulae and is quantified by the abundance discrepancy factor (ADF). In this work, we present a deep integral field spectroscopic
dataset covering the entire Lagoon Nebula (M 8), obtained by the SDSS-V Local Volume Mapper project, at a spatial resolution of 0.21 pc per spaxel. This unique
dataset allows us, for the first time, to investigate spatially resolved maps of oxygen RL intensities (O II V1), together with maps of H I RLs, heavy-ion CELs, and
dust attenuation across a whole H II region. We map the electron temperature using CELs and RLs of $O^{2+}$, CELs of $N^{+}$, and the electron density using CELs of $S^{+}$. We derive CEL-based ionic and elemental oxygen abundances and, for the first time, a spatially resolved map of the RL-based $O^{2+}$ abundance in an H II region. These measurements enable the construction of the first spatially resolved ADF($O^{2+}$) map of an H II region and yield a global mean ADF of ~0.47 +/- 0.02 dex. Focusing on the central region of M 8, where ionization is dominated by the O-type
star Her 36, we find radial variations in the ADF ranging between ~0.35-0.50 dex. Our findings provide novel constraints on the spatial behavior and origin of the abundance discrepancy in H II regions.
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All authors Amrita Singh, Guillermo A. Blanc, Nimisha Kumari, J. E. Méndez-Delgado, Sebastián F. Sánchez, Christophe Morisset, Enrico Congiu, Kathryn Kreckel, Alexandre Roman-Lopes, Oleg Egorov, Niv Drory, Ravi Sankrit, Alfredo Mejía-Narváez, Evgeniya Egorova, Amy M. Jones, Dmitry Bizyaev, Natascha Sattler, Evelyn J. Johnston, Dante Minniti, Rodolfo de J. Zermeño, José G. Fernández-Trincado, Juna A. Kollmeier
Instrumentation and Methods for Astrophysics
LISA science ground segment conventions
Quentin Baghi, Stanislas Babak, Leor Barack et al. (+23 more)
This document sets out the conventions used for data simulations, waveforms, and analysis pipelines within the Distributed Data Processing Centre (DDPC) of the
Laser Interferometer Space
Antenna (LISA). It can also be considered a best practice guide for all publications related to the LISA mission. Topics covered include time-to-frequency transformations, gravitational-wave source parametrization, the instrumental response to gravitational waves, time-delay interferometry, and reference frame definitions.
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All authors Quentin Baghi, Stanislas Babak, Leor Barack, Jean-Baptiste Bayle, Ollie Burke, Raffi Enficiaud, Hector Estelles, Cecilio García Quirós, Olaf Hartwig, Aurelien Hees, Sascha Husa, Henri Inchauspé, Eric Joffre, Antoine Klein, Philip Lynch, Sylvain Marsat, Jonathan Menu, Zach Nasipak, Ramon Pardo De Santayana, Harald Pfeiffer, Lorenzo Pompili, Adam Pound, Geraint Pratten, Antoni Ramos-Buades, Carlos Sopuerta, Niels Warburton
Astrophysics of Galaxies
Little Red and Blue Dots: simply stratified Broad Line Regions
J. Scholtz, F. D'Eugenio, R. Maiolino et al. (+14 more)
It has been claimed that a fraction of the so-called Little Red Dots (LRDs) are characterised by exponential broad line profiles, which have been ascribed to broadening from electron scattering by an ionised cocoon. In this work, we investigate the H$\alpha$ broad line profiles of 32 AGN, including Little Red Dots (LRDs), Little Blue Dots (LBDs), and X-ray detected sources, using high SNR and resolution spectroscopy. We find that while single Gaussian models are statistically rejected, the exponential model is not universally preferred. Lorentzian and multi-Gaussian profiles provide equally good or superior fits for the majority of the sample, with no statistical preference for exponential profiles in $\sim$60% of cases across all AGN subtypes. There are indications that exponential profiles are preferred more frequently among LBDs, indicating that exponential profiles are not a prerogative of LRDs, which actually seem to more often favour Lorentzian profiles. Furthermore, we demonstrate that exponential wings can emerge naturally from the stratification of BLR clouds in virial motion, without invoking any scattering process. More generally, we also show that stacking multiple broad lines (either from multiple objects, as done in previous works, or from different BLR components within the same object) generally yields an exponential profile, even if none of the individual profiles are exponential. Explaining the exponential profiles in terms of BLR stratification solves various observational tensions with the electron scattering interpretation. While electron scattering may play a role, there is no evidence that it dominates the line profiles and that it significantly affects the inferred black hole masses.
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All authors J. Scholtz, F. D'Eugenio, R. Maiolino, M. Brazzini, H. Übler, X. Ji, M. Perna, F. Sun, G. Brocchi, S. Carniani, G. Cresci, L. R. Ivey, I. Juodžbalis, A. Marconi, G. Mazzolari, G. Risaliti, B. Trefoloni
Astrophysics of Galaxies
Mainly on the Plane: Observing the Extended, Ionized Disks of Milky Way Analogs in IllustrisTNG
Michael Messere, Kirill Tchernyshyov, Mary E. Putman et al. (+4 more)
This paper explores the extent to which the circumgalactic medium (CGM) of Milky Way-like
galaxies is located in an extended, ionized, disklike structure. To test this hypothesis, we analyze the spatial and kinematic distributions of different ion species within a sample of MW-like systems in IllustrisTNG. We model commonly observed ions (HI, MgII, SiIV, CIV and OVI) and calculate (1) their angular momentum misalignment from the
star-forming disk ($\theta$) and (2) the fraction of absorption consistent with
galaxy rotation ($f_\mathrm{EWcorot}$). We find that 63% of MgII, 45% of SiIV, 38% of CIV, and 35% of OVI mass along the major axis have kinematics aligned with the
galaxy angular momentum axis. We extend this to a mock absorption line survey and quantify $f_\mathrm{EWcorot}$. We find that $f_\mathrm{EWcorot}$(MgII) $\sim80\%$ and $f_\mathrm{EWcorot}$(OVI) $\sim60\%$ at $\sim0.5\ \mathrm{R_{200c}}$, in agreement with recent observational work. We find that in the typical MW analog, there is evidence of cool-warm material in an extended, corotating structure, regardless of whether the angular momentum or observational definition is used. Hence, we expect that the typical MW CGM, especially in the low ions, should be mainly on the plane.
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All authors Michael Messere, Kirill Tchernyshyov, Mary E. Putman, Greg L. Bryan, Jessica K. Werk, Yong Zheng, David Schiminovich
Solar and Stellar Astrophysics
Two hot pre-white dwarfs inside the red-giant-branch planetary nebula Pa 13 – Double core evolution or common envelope-induced rejuvenation?
Nicole Reindl, David Jones, Todd Hillwig et al. (+4 more)
Close binary central
stars of PNe offer a unique window for investigating the conditions immediately following the ejection of a common envelope (CE). Double eclipsing and double-lined double systems are particularly valuable as they provide minimally model-dependent constraints on fundamental binary parameters. We report that the
nucleus of Pa13 (P=0.3988d) belongs to this rare class of systems and present a comprehensive analysis of its double-degenerate binary. We performed a two-component NLTE spectral analysis based on phase-resolved X-Shooter spectroscopy, multi-band light-curve modeling, SED fitting, as well as a kinematic analysis. Both
stars are found to be hot pre-white
dwarfs, with
Star1 being cooler but larger (Teff=50kK, R=0.40Rsol) than
Star2 (Teff=75kK, R=0.16Rsol). The weakness of spectral lines of
Star2 made both the atmospheric and RV analyses challenging, and we uncovered a strong sensitivity of the assumed surface ratio to its derived RV curve. Yet, the RV curve and Kiel mass of
Star1 (M1=0.41+/-0.02Msol) could be determined precisely, allowing for a dynamical mass determination of
Star2 (M2=0.39+/-0.04Msol). We uncovered that Pa13 exhibits a small but significant orbital eccentricity (e=0.02+/-0.01), making it only the second post-CE binary
nucleus with a measured eccentricity. We conclude that Pa13 provides hitherto the strongest evidence that PNe can be observed around post-RGB
stars. Immediately after the CE-ejection,
Star1 likely still filled its Roche lobe, suggesting that Pa13 is a more evolved, detached descendant of over-contact double-degenerate systems such as Hen2-428. Since the mass ratio of Pa13 is close to unity the system may have formed through double-core CE
evolution. Alternatively, there must exist an efficient CE-induced rejuvenation mechanism capable of reheating the cool white
dwarf in the binary, as already indicated by Hen2-428. (abbreviated)
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All authors Nicole Reindl, David Jones, Todd Hillwig, Marcelo M. Miller Bertolami, Matti Dorsch, Nicholas Chornay, Max Pritzkuleit
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Dispersion Relations of Collective Flavor Excitations in Dense Neutrino Media
Anson Kost and Huaiyu Duan
We apply the Landau damping theory to collective
flavor excitations in dense
neutrino media. We demonstrate explicitly that the (meta)stable modes of the collective
flavor excitations in a physical dense
neutrino gas are indeed weakly damped. We show that, in a
neutrino medium with a continuous energy distribution, there can exist infinitely many dispersion relation branches of collective
flavor excitations that extend to large wave numbers. In a
neutrino gas with one or more zero crossings in the distribution of the difference of the (
neutrino)
lepton numbers (DLNs), the least damped resonant branches and the metastable branches can suffer from inverse Landau damping at certain wave numbers and thus become unstable. We also introduce the concept of convolved DLN distributions, which can be used to understand the physical origin of the slow and fast
flavor instabilities in dense
neutrino media in core-collapse
supernovae and
neutron star mergers.
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Astrophysics of Galaxies
A Bending in the Size-mass Relation of Star-forming Galaxies across $0.5 < z < 6.0$ at a Critical Stellar Mass of $10^{10}M_\odot$ Revealed by JWST
Longyue Chen, Tao Wang, Hanwen Sun et al. (+12 more)
We investigate the rest-frame optical size-
stellar mass relation of
galaxies at $0.5<z<6.0$ using deep JWST/NIRCam and MIRI imaging from the PRIMER survey. We find that
star-forming
galaxies (SFGs) exhibit a broken power-law relation at all
redshifts, with a nearly constant pivot mass ($M_{\rm p}$) of $\sim 10^{10} M_\odot$, and a slope flattening above $M_{\rm p}$. This highlights the prevalence of a population of compact, massive SFGs that was underrepresented in previous studies. The size distribution of quiescent
galaxies (QGs) is well described by a mixture power-law model, with a pivot mass that increases from $M_{\rm p} \sim 10^{10.0} M_\odot$ at $z =0.75$ to $M_{\rm p} \sim 10^{10.5} M_\odot$ at $z = 2.6$, suggesting that the minimum
halo mass required to quench high-mass
galaxies increases with
redshift. The bending in the size-mass relation of SFGs supports two distinct size growth modes. At $M_{\star} < M_{\rm p}$, size growth is closely coupled to
halo growth, while at $M_{\star} > M_{\rm p}$, an increasing fraction of SFGs decouple from
halo growth and become compact, likely associated with rapid bulge (and black hole) growth in $M_{\rm h} \gtrsim 10^{12} M_{\odot}$
halos. These compact SFGs are promising progenitors of massive QGs, as evidenced by their similar masses, surface brightness profiles, and morphologies. Their high number densities can account for the observed buildup of massive QGs at $z > 2$, suggesting that the compaction pathway, rather than major mergers of extended SFGs, dominates the formation of high-z massive QGs.
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All authors Longyue Chen, Tao Wang, Hanwen Sun, Ke Xu, Luwenjia Zhou, Tiancheng Yang, Maxime Tarrasse, Houjun Mo, Zhaozhou Li, Yangyao Chen, Avishai Dekel, Emanuele Daddi, Xuheng Ding, Mauro Giavalisco, David Elbaz
Earth and Planetary Astrophysics
QLP Data Release Notes 004: TESS-Gaia Light Curve Photometry Implementation
Glen Petitpas, Jack Haviland, Te Han et al. (+7 more)
The Quick-Look Pipeline (QLP; Huang et al. 2020, Kunimoto et al. 2021 and references therein) generates light curves for up to 2 million
stars every 27.4 days observed by TESS as part of its
planet search. As machine learning methods enable deeper searches and scientific priorities shift toward fainter
stars, there is a motivation for QLP to perform better at fainter magnitudes. We have adopted the photometry methods employed by the TESS-
Gaia Light Curve package (Han & Brandt 2023), which has been shown to have better noise characteristics than the original QLP photometry from 10.5 $<$ $T$ $<$ 13.5. We still perform aperture photometry and deliver 3 apertures, and 3 levels of detrending for all
stars brighter than $T$ = 13.5, so the changes should be seamless for external users. This method is implemented as of Sector 94 in QLP light curves and is providing users with higher precision light curves and allows detection of fainter signals in our
planet searches.
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All authors Glen Petitpas, Jack Haviland, Te Han, Willie Fong, Katharine Hesse, Avi Shporer, Jeroen Audenaert, Daniel Muthukrishna, Roland Vanderspek, George R. Ricker
Astrophysics of Galaxies
Axionlike dark-matter winds driven by galactic baryon redistribution
A.V. Nazarenko
We examine solutions of the hydrodynamic equations for dark matter (DM) modeled as a Bose-Einstein condensate (BEC) with
axion-like interaction, forming a spherically symmetric
halo in
dwarf galaxies. Small perturbations and macroscopic decoherence of the BEC DM are driven by variations in the local gravitational background induced by subgalactic baryonic redistribution. Focusing on the core region of a
dwarf galaxy, we analyze three astrophysical scenarios parametrized by observational data for NGC 2366: (i) expansion of a gaseous shell mimicking
stellar explosions, (ii) collapse of a shell modeling
star formation, and (iii) inward contraction of a
stellar cluster driven by dynamical friction within a gaseous environment. Our linearized hydrodynamic simulations reveal that while central DM density variations remain within a subtle 0.01% margin, the induced DM winds are extremely suppressed, reaching velocities of only up to several meters per second. This striking suppression challenges the observational prospect of detecting dark-wind signatures. To address the long-term cumulative impact of multiple baryonic events, we establish a
quantum excitation framework with a discrete spectrum under natural Robin boundary conditions. In the inhomogeneous DM
halo background, which includes an unstable phase region, the lowest long-wavelength radial mode acts as a false
vacuum state, experiencing non-viscous
quantum relaxation and decaying over a characteristic lifetime of 68 Myr. This mechanism triggers a universal exponential damping of the system's evolutionary operator, while nonlinear three-mode parametric energy exchange, rather than standard open-continuum Beliaev damping, emerges in the next order of perturbation theory to govern the redistribution of stable quasiparticle excitations.
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High Energy Astrophysical Phenomena
Characterizing Short-Timescale Optical Variability in Non-blazar Active Galactic Nucleus PKS~0521$-$36 Using TESS
Sikandar Akbar and Zahir Shah
We present a systematic analysis of high-cadence optical light curves of the non-blazar AGN PKS~0521$-$36 obtained with TESS across three sectors: Sectors~5 and~6 (Cycle~1, 30~min cadence) and Sector~32 (Cycle~3, 10~min cadence). The source exhibits moderate variability with $F_\mathrm{var} \approx 0.69$–$1.19\%$, consistent with a mildly beamed jet. The power spectral density (PSD) in all sectors is better described by a bending power-law than a simple power law, with high-frequency slopes $\alpha_1 \approx 2.1$–2.9, indicating red-noise dominated variability. Flux distributions require two-component models, with a double log-normal providing the best description, suggesting the presence of two distinct optical flux states associated with quiescent jet emission and episodic flaring activity. A significant QPO at $P = 2.838 \pm 0.078$~d is detected in Sector~5 at $>99.99\%$ confidence in the Lomb–Scargle periodogram, independently confirmed by WWZ ($2.839 \pm 0.110$~d) and supported at the $3\sigma$ level by DRW analysis. The signal spans $\sim$9 cycles within the 26.1-day baseline in Sector~5 and is absent in Sectors~6 and~32, indicating a transient feature. The PSD bending frequency ($\nu_b \approx 0.308$~d$^{-1}$; $\sim$3.2~d) is consistent with the QPO period, suggesting a common origin. We interpret the oscillation as magnetohydrodynamic kink instabilities in the relativistic jet, consistent with the observed helicoidal structure. A moderate Doppler factor ($\delta \approx 5$–10) naturally explains the day-scale periodicity. Together with previously reported $\gamma$-ray QPOs on longer timescales, this suggests a hierarchical variability structure, and, to the best of our knowledge, provides the first evidence for an optical QPO in a non-blazar AGN with a directly imaged helical jet.
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Solar and Stellar Astrophysics
Simulations of massive star atmospheres and winds during giant eruptive and quiescent luminous blue variable phases
P. Schillemans, J.O. Sundqvist, D. Debnath et al. (+3 more)
Mass loss from massive
stars located in the part of the Hertzsprung-Russell diagram (HRD) where we find luminous blue variables (LBVs) is profoundly important for
stellar evolution yet poorly understood. We use time-dependent radiation-hydrodynamic (RHD) simulations to examine the atmosphere and wind properties of such massive
stars, computing 2D and 1D RHD models of the coupled envelopes, atmospheres, and wind
outflows, tuned to this region in the HRD. Our unified simulations start deep in the
stellar envelope (well below T ~ 200 kK) and include the outflowing wind, accounting for line-driving, radiative enthalpy, and
photon tiring. Mass-loss rates, wind speeds, and the radiative luminosity at the photosphere are emergent properties in the simulations. A grid of models is created by slightly increasing the
stellar energy at the lower boundary. This results in a natural transition from very turbulent atmospheres with line-driven winds to effectively stationary super-Eddington massive
outflows. Our sub-Eddington models are essentially blue hypergiant
stars with very variable surfaces, effective mass-loss rates $\dot{M} \sim 2 - 5 \times 10^{-5}$ $M_{\odot}$/year, and wind speeds $v_{\infty} \sim 200 - 300$ km/s, resembling quiescent LBVs like P Cygni. The super-Eddington models have optically thick wind envelopes and extremely inflated yellow surfaces (Teff ~ 5000 K), $\dot{M} \sim 0.1 - 1$ $M_{\odot}$/year, and $v_{\infty} \sim 400 - 500$ km/s, resembling a massive
star during a great eruption like eta Carinae's. Our models naturally reproduce the overall characteristic
stellar and wind parameters inferred for massive
stars in their quiescent LBV and yellow
giant eruptive phases. It remains an open question whether the energy increase needed to trigger a
giant eruption can be obtained solely by the internal
evolution of the
star itself or if it requires an external energy source.
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All authors P. Schillemans, J.O. Sundqvist, D. Debnath, L. Delbroek, N. Moens, C. Van der Sijpt
Astrophysics of Galaxies
J-PAS: unprecedented precision in stellar populations of diffuse tidal features
Sepideh Eskandarlou, Mohammad Akhlaghi, Francisco Arizo-Borillo et al. (+38 more)
Galaxies frequently interact with nearby systems, a process that can significantly alter their morphology and
star formation activity. However, spectroscopic studies of their faint and diffuse remnants require very long exposure times and often exceed the limited field of view of integral field units (IFUs). On the other hand, broad-band imaging can have a much wider field of view, but lacks the spectral resolution to identify key spectral features, restricting accurate constraints on
stellar population properties. With its 54 narrow-band filters in the optical and wide coverage (planned 8000 square degrees), J-PAS fills this gap. In this case study, we examine PGC 3087775, a massive
galaxy at z = 0.046179 (~ 201 Mpc) in the later stages of a major merger in the J-PAS early data release. Photometry was validated with MaNGA IFU data (for the central part).
Stellar population properties was derived using both J-PAS and SDSS photometry. SDSS indicates a metal-rich population with an extended
star formation history (SFH) and elevated
star formation rates. J-PAS instead points to a less metal-rich population with moderate extinction and a more rapid SFH, consistent with a quenched
stellar population. The average Dn(4000) index of the
tidal features is 1.24, suggesting that it was a non-dry merger and a fourfold improvement in the precision of
stellar mass and Dn (4000) was found with J-PAS. We also assessed two heuristic methods for estimating the mass-to-light ratio from SDSS filters and found that they overestimate the
stellar mass in this
galaxy by 0.5 dex and 0.4 dex relative to SED fitting results from J-PAS and SDSS, respectively. Future work will extend this analysis to a larger sample of merging
galaxies and
evolution of the
stellar populations of such structures across the nearby Universe to unprecedented detail. This project is fully reproducible, through Maneage (commit 0f0d7e2).
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All authors Sepideh Eskandarlou, Mohammad Akhlaghi, Francisco Arizo-Borillo, Johan H. Knapen, Helena Domínguez Sánchez, Juan Antonio Fernández-Ontiveros, Carlos López-Sanjuan, Rosa María González Delgado, Yolanda Jiménez Teja, Renato Dupke, Yves Revaz, Pascale Jablonka, Santi Roca-Fábrega, Juan Miró-Carretero, David Martínez-Delgado, Alejandro Lumbreras-Calle, Antonio Hernán-Caballero, Héctor Vázquez Ramió, Raúl Infante-Sainz, Ana L. Chies-Santos, Alessandro Ederoclite, Julio Esteban Rodríguez Martín, Raul Abramo, Jailson Alcaniz, Narciso Benitez, Silvia Bonoli, Javier Zaragoza, Saulo Carneiro, Javier Cenarro, David Cristóbal-Hornillos, Simone Daflon, Carlos Hernández-Monteagudo, Jifeng Liu, Antonio Marín Franch, Claudia Mendes de Oliveira, Mariano Moles, Fernando Roig, Laerte Sodré Jr., Keith Taylor, Jesús Varela, José Manuel Vilchez
High Energy Astrophysical Phenomena · Cross-listed from nucl-th
S-wave kaon condensation in neutron-star matter within a chiral model framework with dynamical meson masses
Yuhan Wang, Rajesh Kumar, Joaquin Grefa et al. (+4 more)
We investigate s-wave kaon condensation in dense matter and
neutron stars within the updated
Chiral Mean Field model with an improved
meson description (mCMF), which incorporates dynamically generated in-medium
meson masses arising from explicit
chiral symmetry breaking and vector-
meson self-interactions. In contrast to conventional relativistic mean-field descriptions with constant
meson masses, the mCMF framework introduces a self-consistent feedback between the
meson sector and the dense-matter equations of motion. The kaon dispersion relation is derived from the nonlinear SU(3) Lagrangian, including the Weinberg-Tomozawa interaction and additional
baryon-pseudoscalar couplings, and the onset of condensation is determined under conditions of charge neutrality and $\beta$
equilibrium. Our calculations include the full
baryon octet together with electrons and
muons at zero temperature. We analyze the impact of hyperons,
muons, and kaon condensation on the equation of state, on
neutron-
star mass–radius relations, and
neutron-
star thermal
evolution, and examine the sensitivity of the onset density and
stellar properties to variations in the nucleon–kaon scattering length and to different model vector parameters and vector self-interactions. We find that $K^{-}$ condensation sets in between $n \sim (2-8)\, n_0$ (in units of
nuclear saturation density) and leads to a moderate to strong softening (in one case, a slight stiffening of the equation of state), depending on the interplay of kaons and hyperons, while remaining compatible with current $2\,M_\odot$ and small-radius
neutron-
star observational constraints and producing distinguishable behavior in the
neutron-
star cooling. This work provides an improved and thermodynamically consistent framework for studying exotic degrees of freedom in
neutron-
star matter.
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All authors Yuhan Wang, Rajesh Kumar, Joaquin Grefa, Konstantin Maslov, Claudia Ratti, Rodrigo Negreiros, Veronica Dexheimer
Solar and Stellar Astrophysics
Oliver Rice and Anthony Yeates
We expand upon our paper (Rice and Yeates, 2021) which introduced `
Outflow Fields': alternatives to the widely-used potential field source surface (PFSS) extrapolations of the Sun's coronal
magnetic field which take into account the effect of the
solar Wind. We showed that our fields have several advantages over PFSS, namely more accurate measurements of the Open
Solar Flux (OSF) relative to observations, more realistic streamer shapes and less dependence on the arbitrary source-surface height. In this paper we seek to quantify these improvements. This includes comparison of
magnetic field line angles with eclipse photography, an improved
solar wind solution model and the introduction of data from a wider range of observations. We use these comparisons to determine the optimum parameters for our model using an evolutionary
algorithm, in addition to the creation of synthetic eclipse images. We find that our
Outflow Fields can accurately capture the overall
topology of the
magnetic field, and reduce the well-known discrepancy with in-situ
magnetic field measurements by a significant margin relative to PFSS. Specifically, over the period between 2000 and 2022 for a typical source-surface height we find that optimized
Outflow fields reduce this discrepancy from around 45% to 24% while also matching the field line
topology seen during eclipse photography. Our model is presented for wider use by the community as a new python package "outflowpy".
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Cosmology and Nongalactic Astrophysics
Using Global Gravitational Potential Weighted Correlation Function to Constrain Modified Gravity Models
Yizhao Yang, Yu Yu and Pengjie Zhang
We propose a new marked two-point correlation function weighted by the global gravitational potential as a probe for testing
gravity models. Using the LCDM model based on general relativity (GR) as a reference, we investigate two representative modified
gravity (MG) scenarios: f(R)
gravity and nDGP. The mark used in this work, the global gravitational potential that is reconstructed from the
galaxy distribution via the Poisson equation, is in contrast to the local property based mark (e.g., local
galaxy number density or gravitational potential of host
halo) used in previous studies. By applying two weighting schemes to quantify environment-dependent clustering, we find that this statistic is able to distinguish MG models from GR, with the signal being enhanced in regions corresponding to particular ranges of gravitational potential. These results indicate that the proposed statistic can serve as a useful complement to conventional clustering probes in future surveys, once observational effects and modeling uncertainties are properly taken into account.
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Astrophysics of Galaxies
The SPHEREx Ices Investigation: An Overview
Gary J. Melnick, Joseph L. Hora, Matthew L. N. Ashby et al. (+26 more)
SPHEREx is a NASA mission designed to perform an all-sky spectroscopic survey in the 0.75 - 5 $\mu$m wavelength range. Its primary science objectives are to investigate: (1) inflationary cosmology, (2) the history of
galaxy formation, and (3) the abundance of molecular ices - critical for prebiotic chemistry - found on the surfaces of interstellar
dust grains within
planet-forming regions. This paper focuses on the third theme, the SPHEREx Ices investigation, for which SPHEREx is conducting a spectroscopic survey of nearly ten million preselected sources throughout the Milky Way and Magellanic Clouds to characterize their ice absorption features. By selecting targets based on infrared color, spatial isolation, and brightness, the Ices Investigation secures high-signal-to-noise spectra across a broad range of astrophysical environments that are relatively free of spectral contamination. Rather than attempting to decompose each spectrum into its individual ice components, the Ices Investigation prioritizes accurate measurements of the integrated optical depths of key molecular ice absorption features. This approach enables statistically powerful correlation studies between ice abundances and environmental parameters - including extinction, temperature, gas composition, radiation field strength,
cosmic ray flux, and
star formation activity. The data pipeline developed for this purpose incorporates machine learning for continuum estimation, drawing on both SPHEREx and ancillary
datasets. Ultimately, the expansive spectral archive produced by SPHEREx, combined with targeted follow-up from facilities like JWST, will transform our understanding of
Galactic ice formation,
evolution, abundance and their inheritance into planetary systems and prebiotic inventories.
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All authors Gary J. Melnick, Joseph L. Hora, Matthew L. N. Ashby, Volker Tolls, Jaeyeong Kim, Carey M. Lisse, Roberta Paladini, Michael W. Werner, Jeong-Eun Lee, Young-Jun Kim, Miju Kang, Yun-Ting Cheng, James J. Bock, Brendan P. Crill, Ari Cukierman, Olivier Dore, Andreas Faisst, Howard Hui, Woong-Seob Jeong, Chul-Hwan Kim, Ho-Gyu Lee, Jae-Joon Lee, Daniel Masters, Chi H. Nguyen, Jinyoung Noh, Ji Yeon Seok, Soung-Chul Yang, Yujin Yang, Michael Zemcov
Cosmology and Nongalactic Astrophysics
Probing the Cosmic Web with Fast Radio Bursts. I. Scattering
Sharon Lapiner, Nir Mandelker, Paz Beniamini et al. (+1 more)
We study the formation of multiphase gas in the post-
accretion-shock regions of
cosmic sheets, filaments, and the circumgalactic medium (CGM) of
haloes, i.e.,
cosmic web objects (CWOs). Local instabilities in the hot medium result in fragmentation and cooling, eventually forming small-scale overdensities with temperatures of $\sim 10^{4}{\,\rm K}$ in pressure
equilibrium with the hot environment. Such dense, ionised inhomogeneities can affect the propagation of
radio waves from fast
radio bursts (FRBs), thereby offering us a way to probe their presence and properties in CWOs through scattering signatures in the observed FRB flux. We find that high-$z$ filaments & sheets have a negligible contribution to the total observed scattering. The high rates of FRBs expected even at high
redshifts may still allow detection from high-temperature filaments along rare sightlines, and we suggest other methods for such systems in a companion paper. Our model further predicts that if turbulent cloudlets exist in the CGM of intervening massive
haloes with a volume-filling fraction of $f_{\rm v}\gtrsim 10^{-3}$, they are expected to cause considerable cumulative scattering along an average sightline, resulting in a significant correlation between the total scattering time and source
redshifts. The lack of such a correlation in current observations may imply that the cool gas in the CGM has substantial non-thermal pressure, reducing its density, or significant damping of small-scale density fluctuations. Forthcoming localised FRB samples can map these constraints into bounds on volume-filling fractions, densities, cloud sizes, and the strength of
turbulence.
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All authors Sharon Lapiner, Nir Mandelker, Paz Beniamini, S. Peng Oh
High Energy Astrophysical Phenomena
Investigation of the Microquasar SS 433 with VERITAS
The VERITAS Collaboration: A. Archer, P. Bangale, J. T. Bartkoske et al. (+56 more)
Microquasars such as SS 433 are considered potential contributors to
cosmic rays up to the knee of the
cosmic ray energy spectrum ($\sim4\,\mathrm{PeV}$), where a transition in the dominant acceleration processes is expected. The SS 433 system, located within the W50
supernova remnant, is a
Galactic microquasar with relativistic jets interacting with the surrounding medium over parsec scales, providing an example for studying jet-driven particle acceleration. A deep morphological and spectral study of SS 433 is performed using more than 150 hours of observations with VERITAS, sensitive to $\gamma$-ray energies $>100\,\mathrm{GeV}$. With an angular resolution better than $0.1^\deg$, extended TeV $\gamma$-ray emission is resolved from both the eastern and western jet lobes, located tens of parsecs from the central binary. The emission appears elongated along the jet axis and coincides with regions where the jets interact with the surrounding
supernova remnant. No TeV emission is detected from the central binary, nor is significant emission observed between the central binary and the jet lobes. Phase-resolved analyses show no evidence for variability with orbital or precessional phase, supporting a steady emission scenario. The observed morphology and spectra are consistent with scenarios where particles are accelerated in the lobes of the jets, possibly through shocks or alternative processes such as
magnetic reconnection. The extended TeV emission from the jet lobes of SS 433 favors a leptonic origin in the VERITAS energy range, suggesting any hadronic acceleration is subdominant. The results offer valuable constraints on how microquasar jets may contribute to the
Galactic cosmic-ray population toward the knee.
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All authors The VERITAS Collaboration: A. Archer, P. Bangale, J. T. Bartkoske, W. Benbow, N. R. Bond, Y. Chen, J. L. Christiansen, A. J. Chromey, A. Duerr, M. Errando, M. E. Godoy, J. E. Pedrosa, S. Feldman, Q. Feng, S. Filbert, A. Furniss, W. Hanlon, O. Hervet, C. E. Hinrichs, J. Holder, T. B. Humensky, M. Iskakova, W. Jin, M. N. Johnson, E. Joshi, P. Kaaret, M. Kertzman, M. Kherlakian, T. K. Kleiner, N. Korzoun, F. Krennrich, S. Kumar, S. Kundu, M. J. Lang, M. Lundy, G. Maier, P. Moriarty, R. Mukherjee, M. Ohishi, R. A. Ong, A. Pandey, M. Pohl, E. Pueschel, P. L. Rabinowitz, K. Ragan, P. T. Reynolds, D. Ribeiro, E. Roache, I. Sadeh, L. Saha, H. Salzmann, M. Santander, G. H. Sembroski, S. Tandon, J. V. Tucci, D. A. Williams, S. L. Wong, J. Woo, T. Yoshikoshi