adsabs/SciX_UAT_keywords huggingface dataset:
Double Image Polarimeter—Ultra Fast: Simultaneous Three-color (BV R) Polarimeter with Electron-multiplying Charge-coupled Devices

We describe a new instrument capable of high-precision (10-5) polarimetric observations simultaneously in three passbands (BVR). The instrument utilizes electron-multiplying charge-coupled device (EM CCD) cameras for high efficiency and fast image readout. The key features of the Double Image Polarimeter—Ultra Fast (DIPol-UF) are: (i) the optical design with high throughput and inherent stability; (ii) great versatility, which makes the instrument optimally suitable for observations of bright and faint targets; and (iii) a control system, which allows the use of the polarimeter remotely. Examples are given of the first results obtained from high signal-to-noise observations of bright nearby stars and of fainter sources such as X-ray binaries in their quiescent states.

Keywords: observational astronomy; polarimeters; photometer; polarimetry; high energy astrophysics; black holes; binary stars
Shock Breakout in Three-dimensional Red Supergiant Envelopes

Using Athena++, we perform 3D radiation-hydrodynamic calculations of the radiative breakout of the shock wave in the outer envelope of a red supergiant (RSG) that has suffered core collapse and will become a Type IIP supernova. The intrinsically 3D structure of the fully convective RSG envelope yields key differences in the brightness and duration of the shock breakout (SBO) from that predicted in a 1D stellar model. First, the lower-density "halo" of material outside of the traditional photosphere in 3D models leads to a shock breakout at lower densities than 1D models. This would prolong the duration of the shock breakout flash at any given location on the surface to ≈1-2 hr. However, we find that the even larger impact is the intrinsically 3D effect associated with large-scale fluctuations in density that cause the shock to break out at different radii at different times. This substantially prolongs the SBO duration to ≈3-6 hr and implies a diversity of radiative temperatures, as different patches across the stellar surface are at different stages of their radiative breakout and cooling at any given time. These predicted durations are in better agreement with existing observations of SBO. The longer durations lower the predicted luminosities by a factor of 3-10 (L bol ~ 1044 erg s-1), and we derive the new scalings of brightness and duration with explosion energies and stellar properties. These intrinsically 3D properties eliminate the possibility of using observed rise times to measure the stellar radius via light-travel time effects.

Keywords: supernovae; type ii supernovae; hydrodynamical simulations; massive stars; radiative transfer
Constraining the Dense Matter Equation of State with Joint Analysis of NICER and LIGO/Virgo Measurements

The Neutron Star Interior Composition Explorer collaboration recently published a joint estimate of the mass and the radius of PSR J0030+0451, derived via X-ray pulse-profile modeling. Raaijmakers et al. explored the implications of this measurement for the dense matter equation of state (EOS) using two parameterizations of the high-density EOS: a piecewise-polytropic model, and a model based on the speed of sound in neutron stars (NSs). In this work we obtain further constraints on the EOS following this approach, but we also include information about the tidal deformability of NSs from the gravitational wave signal of the compact binary merger GW170817. We compare the constraints on the EOS to those set by the recent measurement of a 2.14 M⊙ pulsar, included as a likelihood function approximated by a Gaussian, and find a small increase in information gain. To show the flexibility of our method, we also explore the possibility that GW170817 was a NS-black hole merger, which yields weaker constraints on the EOS.

Keywords: neutron star cores; gravitational waves; millisecond pulsars; rotation powered pulsars; bayesian statistics; nuclear physics; nuclear astrophysics; x-ray astronomy
Breakthrough Listen Search for the WOW! Signal

Caballero identified the star 2MASS 19281982-2640123 as a potential Sun-like star from which the WOW! signal could have originated. We conducted a search for artificial narrowband (2.79 Hz/1.91 Hz), drifting (±4 Hz s-1) technosignatures from this source using the TURBOSETI pipeline, from 1-2 GHz, using simultaneous multi-telescope observations with both the Robert C. Byrd Green Bank Telescope and the newly refurbished Allen Telescope Array on 2022 May 21. Both telescope observations had an overlap of 580 s. While blind searches using radio telescopes have been conducted in the general field of view in which the WOW! signal was first detected, this is the first time a targeted search has been done. No technosignature candidates were detected. *Dedicated to the memory of Bart S. Wlodarczyk-Sroka.

Keywords: technosignatures; search for extraterrestrial intelligence; radio astronomy; biosignatures
Nature versus Nurture: Revisiting the Environmental Impact on Star Formation Activities of Galaxies

We present a systematic study of the environmental impact on star formation activities of galaxies using a mass-complete sample of ~170k galaxies at z < 4 from the latest COSMOS2020 catalog. At z < 1, we find that the mean star formation rate (SFR) of all galaxies decreases with increasing density of the environment. However, when we only consider star-forming galaxies, the mean SFR becomes independent of the environment at z < 1. At z > 2, we observe a clear positive correlation between the SFR and the density of the environment for all the galaxies. On the other hand, the stellar mass of the galaxies increases significantly with the environment at all redshifts except for star-forming galaxies at z < 1. The fraction of quiescent galaxies increases with increasing density of the environment at z < 2, and the morphology-density relation is confirmed to be present up to z ~ 1. We also find that environmental quenching is negligible at z > 1, whereas mass quenching is the dominant quenching mechanism for massive galaxies at all redshifts. Based on these results, we argue that stellar mass-regulated physical processes might be the major driving force for star formation activities of galaxies. At low redshift (z < 1) massive galaxies are quenched primarily due to their high mass, resulting in a normal SFR-density relation. At high redshift (z > 2) most of the galaxies are star-forming ones tightly following the star-forming main sequence, and the difference in their stellar mass in different environments naturally leads to a reversal of the SFR-density relation.

Keywords: galaxy environments
TREX: Kinematic Characterization of a High-dispersion Intermediate-age Stellar Component in M33

The dwarf galaxy Triangulum (M33) presents an interesting testbed for studying stellar halo formation: it is sufficiently massive so as to have likely accreted smaller satellites, but also lies within the regime where feedback and other "in situ" formation mechanisms are expected to play a role. In this work, we analyze the line-of-sight kinematics of stars across M33 from the TREX survey, with a view to understanding the origin of its halo. We split our sample into two broad populations of varying age, comprising 2032 "old" red giant branch stars and 671 "intermediate-age" asymptotic giant branch and carbon stars. We find decisive evidence for two distinct kinematic components in both the old and intermediate-age populations: a low-dispersion (~22 km s-1) disk-like component corotating with M33's H I gas and a significantly higher-dispersion component (~50-60 km s-1) that does not rotate in the same plane as the gas and is thus interpreted as M33's stellar halo. While kinematically similar, the fraction of stars associated with the halo component differs significantly between the two populations: this is consistently ~10% for the intermediate-age population, but decreases from ~34% to ~10% as a function of radius for the old population. We additionally find evidence that the intermediate-age halo population is systematically offset from the systemic velocity of M33 by ~25 km s-1, with a preferred central LOS velocity of ~ - 155 km s-1. This is the first detection and characterization of an intermediate-age halo in M33, and suggests in situ formation mechanisms, as well as potentially tidal interactions, have helped shaped it.

Keywords: triangulum galaxy; galaxy stellar halos; galaxy kinematics
Catching the Butterfly and the Homunculus of η Carinae with ALMA

The nature and origin of the molecular gas component located in the circumstellar vicinity of η Carinae are still far from being completely understood. Here, we present Atacama Large Millimeter/submillimeter Array CO(3-2) observations with a high angular resolution (~0.″15) and a great sensitivity that are employed to reveal the origin of this component in η Carinae. These observations reveal much higher velocity (-300 to +270 km s-1) blue- and redshifted molecular thermal emission than previously reported, which we associate with the lobes of the Homunculus Nebula, and which delineates very well the innermost contours of the red- and blueshifted lobes likely due to limb brightening. The inner contour of the redshifted emission was proposed to be a disrupted torus, but here we reveal that it is at least part of the molecular emission originating from the lobes and/or the expanding equatorial skirt. On the other hand, closer to systemic velocities (±100 km s-1), the CO molecular gas traces an inner butterfly-shaped structure that is also revealed at near-IR and mid-IR wavelengths as the region in which the shielded dust resides. The location and kinematics of the molecular component indicate that this material has formed after the different eruptions of η Carinae.

Keywords: evolved stars
Role of Polycyclic Aromatic Hydrocarbons with Edge Defects in Explaining Astronomical Infrared Emission Observations

A systematic study was performed on the spectral properties of polycyclic aromatic hydrocarbons (PAHs) with edge defects using harmonic density functional theory calculations. Their potential astronomical relevance was assessed through direct comparison with NIRSpec and MIRI-MRS spectra of the atomic photodissociation region of the Orion Bar from the JWST Early Release Science PDRs4All program. It is found that the astronomical 6.2 μm PAH emission band, including its blue side, is well reproduced by PAHs with edge defects, when taking into account the effects of polarization in the computations, and without a need for PAHs that contain nitrogen. Small neutral PAHs with edge defects explain the blue wing of the 3.3 μm band. A low number of edge defects is required to reproduce the 8.6 and 11.2 μm band profiles, while the 11.0 + 11.2/12.7 μm band intensity ratio is a measure for the number of edge defects. A blind database fit to the Orion Bar spectrum reproduces the 6–15 μm region with an error of 9.9% and shows a clear delineation of charge, with the 6–10 μm PAH bands being carried by PAH cations and the 10–15 μm region by predominantly neutral PAHs. The contribution of anions is negligible. Armchair PAHs fit the 12.7 μm band, simultaneously producing a very weak broad emission feature centered at 3.225 μm. Zigzag PAHs fit the 11.2 μm band. It is concluded that PAHs with a low number of edge defects, in addition to armchair and zigzag PAHs, all contribute to the observed interstellar infrared emission.

Keywords: infrared astronomy; molecular spectroscopy
Very-high-energy γ-Ray Emission from Young Massive Star Clusters in the Large Magellanic Cloud

The Tarantula Nebula in the Large Magellanic Cloud is known for its high star formation activity. At its center lies the young massive star cluster R136, providing a significant amount of the energy that makes the nebula shine so brightly at many wavelengths. Recently, young massive star clusters have been suggested to also efficiently produce very high-energy cosmic rays, potentially beyond PeV energies. Here, we report the detection of very-high-energy γ-ray emission from the direction of R136 with the High Energy Stereoscopic System, achieved through a multicomponent, likelihood-based modeling of the data. This supports the hypothesis that R136 is indeed a very powerful cosmic-ray accelerator. Moreover, from the same analysis, we provide an updated measurement of the γ-ray emission from 30 Dor C, the only superbubble detected at TeV energies presently. The γ-ray luminosity above 0.5 TeV of both sources is (2–3) × 1035 erg s‑1. This exceeds by more than a factor of 2 the luminosity of HESS J1646‑458, which is associated with the most massive young star cluster in the Milky Way, Westerlund 1. Furthermore, the γ-ray emission from each source is extended with a significance of >3σ and a Gaussian width of about 30 pc. For 30 Dor C, a connection between the γ-ray emission and the nonthermal X-ray emission appears likely. Different interpretations of the γ-ray signal from R136 are discussed.

Keywords: young star clusters; massive stars; large magellanic cloud; gamma-ray astronomy
Observational Properties of a Bright Type lax SN 2018cni and a Faint Type Iax SN 2020kyg

We present the optical photometric and spectroscopic analysis of two Type Iax supernovae (SNe), 2018cni and 2020kyg. SN 2018cni is a bright Type Iax SN (M V,peak = -17.81 ± 0.21 mag), whereas SN 2020kyg (M V,peak = -14.52 ± 0.21 mag) is a faint one. We derive 56Ni mass of 0.07 and 0.002 M ⊙ and ejecta mass of 0.48 and 0.14 M ⊙ for SNe 2018cni and 2020kyg, respectively. A combined study of the bright and faint Type Iax SNe in R/r-band reveals that the brighter objects tend to have a longer rise time. However, the correlation between the peak luminosity and decline rate shows that bright and faint Type Iax SNe exhibit distinct behavior. Comparison with standard deflagration models suggests that SN 2018cni is consistent with the deflagration of a CO white dwarf, whereas the properties of SN 2020kyg can be better explained by the deflagration of a hybrid CONe white dwarf. The spectral features of both the SNe point to the presence of similar chemical species but with different mass fractions. Our spectral modeling indicates stratification at the outer layers and mixed inner ejecta for both of the SNe.

Keywords: supernovae
SpeX Near-infrared Spectroscopic Extinction Curves in the Milky Way

Interstellar dust extinction curves provide valuable information about dust properties, including the composition and size of the dust grains, and are essential to correct observations for the effects of interstellar dust. In this work, we measure a representative sample of near-infrared (NIR; 0.8-5.5 μm) spectroscopic extinction curves for the first time, enabling us to investigate the extinction at wavelengths where it is usually only measured in broad photometric bands. We use IRTF/SpeX spectra of a sample of reddened and comparison stars to measure 15 extinction curves with the pair method. Our sample spans A(V) values from 0.78 to 5.65 and R(V) values from 2.43 to 5.33. We confirm that the NIR extinction curves are well fit by a power law, with indices and amplitudes differing from sight line to sight line. Our average diffuse NIR extinction curve can be represented by a single power law with index α = 1.7, but because of the sight line-to-sight line variations, the shape of any average curve will depend on the parental sample. We find that most of the variation in our sample can be linked to the ratio of total-to-selective extinction R(V), a rough measurement of the average dust grain size. Two sight lines in our sample clearly show the ice extinction feature at 3 μm, which can be fitted by a modified Drude profile. We find tentative ice detections with slightly over 3σ significance in two other sight lines. In our average diffuse extinction curve, we measure a 3σ upper limit of A(ice)/A(V) = 0.0021 for this ice feature.

Keywords: interstellar dust; interstellar dust extinction; extinction; reddened stars; interstellar extinction; interstellar reddening; interstellar medium; near infrared astronomy; reddening law; milky way galaxy
Identification of a Low-mass Companion to the White Dwarf SDSS J131730.84+483332.7

We present the discovery of 2MASS J13173072+4833343, a low-mass stellar companion to the ∼5.5 Gyr old white dwarf SDSS J131730.85+483332.8. This companion was discovered through the Backyard Worlds: Planet 9 citizen science collaboration. We obtained a near-infrared spectrum of the companion and determined a spectral type of M8.5. Using the cooling age of the white dwarf, we determined that the stellar companion has a mass of ${0.077}_{-0.017}^{+0.005}$ M⊙, or ${80.2}_{-1.8}^{+0.5}$ MJup, near the substellar boundary.

Keywords: substellar companion stars; binary stars
HST Imaging of the Ionizing Radiation from a Star-forming Galaxy at z = 3.794

We report on the Hubble Space Telescope (HST) detection of the Lyman-continuum (LyC) radiation emitted by a galaxy at redshift z = 3.794 dubbed Ion1. The LyC from Ion1 is detected at 820-890 Å with HST WFC3/UVIS in the F410M band (m410 = 27.60 ± 0.36 mAB, peak signal-to-noise ratio (S/N) = 4.17 in an r = 0"12 aperture) and 700-830 Å with the Very Large Telescope (VLT)/VIMOS in the U band (mU = 27.84 ± 0.19 mAB, peak S/N = 6.7 with an r = 0"6 aperture). A 20 hr VLT/VIMOS spectrum shows low- and high-ionization interstellar metal absorption lines and the P Cygni profile of C IV and Lyα in absorption. The latter spectral feature differs from what observed in known LyC emitters, which show strong Lyα emission. An HST far-UV color map reveals that the LyC emission escapes from a region of the galaxy that is bluer than the rest. The F410M image shows that the centroid of the LyC emission is offset from the centroid of the nonionizing UV emission by 0"12 ± 0"03, corresponding to 0.85 ± 0.21 kpc, and that its morphology is likely moderately resolved. These morphological characteristics favor a scenario where the LyC photons produced by massive stars escape from low H I column density "cavities" in the interstellar medium. We also collect the VIMOS U-band images of 107 Lyman-break galaxies at 3.40 < zspec < 3.95, I.e., sampling the LyC, and stack them with inverse-variance weights. No LyC emission is detected in the stacked image, resulting in a 32.5 mAB flux limit (1σ) and an upper limit of absolute LyC escape fraction fescabs ≤ 0.63%.

Keywords: reionization; high-redshift galaxies; extragalactic astronomy
SolO/EUI Observations of Ubiquitous Fine-scale Bright Dots in an Emerging Flux Region: Comparison with a Bifrost MHD Simulation

We report on the presence of numerous tiny bright dots in and around an emerging flux region (an X-ray/coronal bright point) observed with SolO's EUI/HRIEUV in 174 Å. These dots are roundish and have a diameter of 675 ± 300 km, a lifetime of 50 ± 35 s, and an intensity enhancement of 30% ± 10% above their immediate surroundings. About half of the dots remain isolated during their evolution and move randomly and slowly (<10 km s-1). The other half show extensions, appearing as a small loop or surge/jet, with intensity propagations below 30 km s-1. Many of the bigger and brighter HRIEUV dots are discernible in the SDO/AIA 171 Å channel, have significant emissivity in the temperature range of 1-2 MK, and are often located at polarity inversion lines observed in SDO/HMI LOS magnetograms. Although not as pervasive as in observations, a Bifrost MHD simulation of an emerging flux region does show dots in synthetic Fe IX/X images. These dots in the simulation show distinct Doppler signatures-blueshifts and redshifts coexist, or a redshift of the order of 10 km s-1 is followed by a blueshift of similar or higher magnitude. The synthetic images of O V/VI and Si IV lines, which represent transition region radiation, also show the dots that are observed in Fe IX/X images, often expanded in size, or extended as a loop, and always with stronger Doppler velocities (up to 100 km s-1) than that in Fe IX/X lines. Our observation and simulation results, together with the field geometry of dots in the simulation, suggest that most dots in emerging flux regions form in the lower solar atmosphere (at ≈ 1 Mm) by magnetic reconnection between emerging and preexisting/emerged magnetic field. Some dots might be manifestations of magnetoacoustic shocks through the line formation region of Fe IX/X emission.

Keywords: solar corona; solar magnetic flux emergence; solar magnetic reconnection; solar extreme ultraviolet emission; solar transition region; solar coronal transients; x-ray bright point
Revisiting the Chandra Observation on the Region of PSR J1809-193: Indication of the Existence of an X-Ray Halo and Implication for the Origin of HESS J1809-193

HESS J1809-193 is an extended TeV γ-ray source and the origin of its γ-ray emission remains ambiguous. The pulsar wind nebula (PWN) of PSR J1J1809-193 lying inside the extended γ-ray emission is a possible candidate. Powered by the central pulsar, ultrarelativistic electrons in the PWN can produce radio to X-ray emission through synchrotron and γ-ray emission by inverse Compton (IC) scattering. To check whether this PWN is the counterpart of HESS J1809-193, we analyzed the Chandra X-ray radial intensity profile and spectral index profile of this PWN. We then adopted a one-zone isotropic diffusion model to fit the keV and TeV data. We found diffuse nonthermal X-ray emission extending beyond the PWN, which is likely an X-ray halo radiated by escaping electron/positron pairs from the PWN. A relatively strong magnetic field of ~20 μG is required to explain the spatial evolution of the X-ray spectrum (i.e., the significant softening of the spectrum with increasing distance from the pulsar), which, however, would suppress the IC radiation of pairs. Our result implies that a hadronic component may be needed to explain HESS J1809-193.

Keywords: high energy astrophysics; pulsar wind nebulae; x-ray astronomy; gamma-ray sources; non-thermal radiation sources
The Clustering of Submillimeter Galaxies Detected with ALMA

Previous studies measuring the clustering of submillimeter galaxies (SMGs) have based their measurements on single-dish-detected sources, finding evidence for strong clustering. However, ALMA has revealed that, due to the coarse angular resolution of these instruments, single-dish sources can be composed of multiple sources. This implies that the clustering inferred from single-dish surveys may be overestimated. Here, we measure the clustering of SMGs based on the ALESS survey, an ALMA follow-up of sources previously identified in the LABOCA ECDFS Submillimeter Survey (LESS). We present a method to measure the clustering of ALMA sources that have been previously identified using single-dish telescopes, based on forward modeling both the single-dish and the ALMA observations. We constrain upper limits for the median mass of halos hosting SMGs at 1 < z < 3, finding ${M}_{\mathrm{halo}}\leqslant 2.4\times {10}^{12}\,{M}_{\odot }$ for SMGs with flux densities ${S}_{870}\geqslant 4.0\,$ mJy, which is at least ${3.8}_{-2.6}^{+3.8}$ times lower than the mass inferred based on the clustering of the LESS sources alone. This suggests that the strength of SMG clustering based on single-dish observations was overestimated, and therefore SMGs might be hosted by dark matter halos less massive than has previously been estimated. By extrapolating our models down to flux densities of ${S}_{870}\geqslant 1.2\,\,$ mJy, we find that such SMGs inhabit halos with median mass ${M}_{\mathrm{halo}}\leqslant 3.2\times {10}^{11}\,{M}_{\odot }$ . We conclude that only the brightest ( ${S}_{870}\gtrsim 5-6\,\,$ mJy) SMGs would trace massive structures at z ∼ 2 and only SMGs with ${S}_{870}\gtrsim 6\,\,$ mJy may be connected to massive local elliptical galaxies, quasars at intermediate redshifts, and high-redshift star-forming galaxies, whereas fainter SMGs are unlikely linked to these populations.

Keywords: galaxy evolution; high-redshift galaxies; starburst galaxies; submillimeter astronomy; large-scale structure of the universe; clustering; astronomy data modeling