Sazuna/UAT_keywords huggingface dataset:
Cloud Parameterizations and their Effect on Retrievals of Exoplanet Reflection Spectroscopy. Future space-based direct imaging missions will perform low-resolution (R &lt; 100) optical (0.3-1 μm) spectroscopy of planets, thus enabling reflected spectroscopy of cool giants. Reflected light spectroscopy is encoded with rich information about the scattering and absorbing properties of planet atmospheres. Given the diversity of clouds and hazes expected in exoplanets, it is imperative that we solidify the methodology to accurately and precisely retrieve these scattering and absorbing properties that are agnostic to cloud species. In particular, we focus on determining how different cloud parameterizations affect resultant inferences of both cloud and atmospheric composition. We simulate mock observations of the reflected spectra from three top-priority direct imaging cool giant targets with different effective temperatures, ranging from 135 to 533 K. We perform retrievals of cloud structure and molecular abundances on these three planets using four different parameterizations, each with an increasing level of cloud complexity. We find that the retrieved atmospheric and scattering properties depend strongly on the choice of cloud parameterization. For example, parameterizations that are too simplistic tend to overestimate the abundances. Overall, we are unable to retrieve precise/accurate gravity beyond ±50%. Lastly, we find that even reflected light spectroscopy with a low signal-to-noise ratio of 5 and low R = 40 gives cursory zeroth-order insights into the position of the cloud deck relative to the molecular and Rayleigh optical depth level.

Keywords: Atmospheric clouds, Exoplanet atmospheric composition , Exoplanet atmospheres
The Galactic H II Region Luminosity Function at Radio and Infrared Wavelengths. The Galactic H II region luminosity function (LF) is an important metric for understanding global star formation properties of the Milky Way, but only a few studies have been done, and all use relatively small numbers of H II regions. We use a sample of 797 first Galactic quadrant H II regions compiled from the Wide-field Infrared Survey Explorer Catalog of Galactic H II Regions to examine the form of the LF at multiple infrared and radio wavelengths. Our sample is statistically complete for all regions powered by single stars of type O9.5V and earlier. We fit the LF at each wavelength with single and double power laws. Averaging the results from all wavelengths, the mean of the best-fit single power-law index is ⟨α⟩ = -1.75 ± 0.01. The mean best-fit double power-law indices are ⟨α1⟩ = -1.40 ± 0.03 and ⟨α2⟩ = -2.33 ± 0.04. We conclude that neither a single nor a double power law is strongly favored over the other. The LFs show some variation when we separate the H II region sample into subsets by heliocentric distance, physical size, Galactocentric radius, and location relative to the spiral arms, but blending individual H II regions into larger complexes does not change the value of the power-law indices of the best-fit LF models. The consistency of the power-law indices across multiple wavelengths suggests that the LF is independent of wavelength. This implies that infrared and radio tracers can be employed in place of Hα.

Keywords: Luminosity function, Galaxy structure, H II regions, Milky Way Galaxy
Discovery and Timing of Three Millisecond Pulsars in Radio and Gamma-Rays with the Giant Metrewave Radio Telescope and Fermi Large Area Telescope. We performed deep observations to search for radio pulsations in the directions of 375 unassociated Fermi Large Area Telescope γ-ray sources using the Giant Metrewave Radio Telescope (GMRT) at 322 and 607 MHz. In this paper we report the discovery of three millisecond pulsars (MSPs), PSR J0248+4230, PSR J1207-5050, and PSR J1536-4948. We conducted follow-up timing observations for ∼5 yr with the GMRT and derived phase-coherent timing models for these MSPs. PSR J0248+4230 and J1207-5050 are isolated MSPs having periodicities of 2.60 ms and 4.84 ms. PSR J1536-4948 is a 3.07 ms pulsar in a binary system with an orbital period of ∼62 days about a companion of a minimum mass of 0.32 M⊙. We also present multifrequency pulse profiles of these MSPs from the GMRT observations. PSR J1536-4948 is an MSP with an extremely wide pulse profile having multiple components. Using the radio timing ephemeris we subsequently detected γ-ray pulsations from these three MSPs, confirming them as the sources powering the γ-ray emission. For PSR J1536-4948 we performed combined radio-γ-ray timing using ∼11.6 yr of γ-ray pulse times of arrival (TOAs) along with the radio TOAs. PSR J1536-4948 also shows evidence for pulsed γ-ray emission out to above 25 GeV, confirming earlier associations of this MSP with a ≥10 GeV point source. The multiwavelength pulse profiles of all three MSPs offer challenges to models of radio and γ-ray emission in pulsar magnetospheres.

Keywords: High energy astrophysics, Millisecond pulsars, High time resolution astrophysics, Gamma-ray astronomy, Radio astronomy, Binary pulsars
Technique for Separating Velocity and Density Contributions in Spectroscopic Data and Its Application to Studying Turbulence and Magnetic Fields. Based on the theoretical description of position-position-velocity (PPV) statistics in Lazarian &amp; Pogosyan, we introduce a new technique called the velocity decomposition algorithm (VDA) for separating the PPV fluctuations arising from velocity and density fluctuations. Using MHD turbulence simulations, we demonstrate its promise in retrieving the velocity fluctuations from the PPV cube in various physical conditions and its prospects in accurately tracing the magnetic field. We find that for localized clouds, the velocity fluctuations are most prominent in the wing part of the spectral line, and they dominate the density fluctuations. The same velocity dominance applies to extended H I regions undergoing galactic rotation. Our numerical experiment demonstrates that velocity channels arising from the cold phase of atomic hydrogen (H I) are still affected by velocity fluctuations at small scales. We apply the VDA to H I GALFA-DR2 data corresponding to the high-velocity cloud HVC186+19-114 and high-latitude galactic diffuse H I data. Our study confirms the crucial role of velocity fluctuations in explaining why linear structures are observed within PPV cubes. We discuss the implications of VDA for both magnetic field studies and predicting polarized galactic emission that acts as the foreground for cosmic microwave background studies. Additionally, we address the controversy related to the filamentary nature of the H I channel maps and explain the importance of velocity fluctuations in the formation of structures in PPV data cubes. VDA will allow astronomers to obtain velocity fluctuations from almost every piece of spectroscopic PPV data and allow direct investigations of the turbulent velocity field in observations.

Keywords: Interstellar filaments, Interstellar dynamics, Interstellar atomic gas, Interstellar magnetic fields, Interstellar medium
Refining the E + A Galaxy: A Spatially Resolved Spectrophotometric Sample of Nearby Post-starburst Systems in SDSS-IV MaNGA (MPL-5). Post-starburst galaxies are crucial to disentangling the effect of star formation and quenching on galaxy demographics. They comprise, however, a heterogeneous population of objects, described in numerous ways. To obtain a well-defined and uncontaminated sample, we take advantage of spatially resolved spectroscopy to construct an unambiguous sample of E + A galaxies—post-starburst systems with no observed ongoing star formation. Using data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) Survey, in the fourth generation of the Sloan Digital Sky Survey (SDSS-IV), we have identified 30 E + A galaxies that lie within the green valley of color-stellar mass space. We first identified E + A candidates by their central, single-fiber spectra and (u-r) color from SDSS DR15, and then further required each galaxy to exhibit E + A properties throughout the entirety of the system to three effective radii. We describe our selection criteria in detail, note common pitfalls in E + A identification, and introduce the basic characteristics of the sample. We will use this E + A sample, which has been assembled with stringent criteria and thus re-establishes a well-defined subpopulation within the broader category of post-starburst galaxies, to study the evolution of galaxies and their stellar populations in the time just after star formation within them is fully quenched.

Keywords: Spectroscopy, Galaxy evolution, Spectrophotometry, E+A galaxies
Linear Stability Analysis of a Magnetic Rotating Disk with Ohmic Dissipation and Ambipolar Diffusion. We perform a linear analysis of the stability of isothermal, rotating, magnetic, self-gravitating sheets that are weakly ionized. The magnetic field and rotation axis are perpendicular to the sheet. We include a self-consistent treatment of thermal pressure, gravitational, rotational, and magnetic (pressure and tension) forces together with two nonideal magnetohydrodynamic (MHD) effects (ohmic dissipation and ambipolar diffusion) that are treated together for their influence on the properties of gravitational instability for a rotating sheetlike cloud or disk. Our results show that there is always a preferred length scale and associated minimum timescale for gravitational instability. We investigate their dependence on important dimensionless free parameters of the problem: the initial normalized mass-to-flux ratio μ0, the rotational Toomre parameter Q, the dimensionless ohmic diffusivity ${\tilde{\eta }}_{\mathrm{OD},0}$ , and the dimensionless neutral-ion collision time ${\tilde{\tau }}_{\mathrm{ni},0}$ , which is a measure of the ambipolar diffusivity. One consequence of ${\tilde{\eta }}_{\mathrm{OD},0}$ is that there is a maximum preferred length scale of instability that occurs in the transcritical (μ0 ≳ 1) regime, qualitatively similar to the effect of ${\tilde{\tau }}_{\mathrm{ni},0}$ , but with quantitative differences. The addition of rotation leads to a generalized Toomre criterion (that includes a magnetic dependence) and modified length scales and timescales for collapse. When nonideal MHD effects are also included, the Toomre criterion reverts back to the hydrodynamic value. We apply our results to protostellar disk properties in the early embedded phase and find that the preferred scale of instability can significantly exceed the thermal (Jeans) scale and the peak preferred fragmentation mass is likely to be ∼10-90 MJup.

Keywords: Magnetohydrodynamics, Gravitational instability, Star forming regions, Interstellar magnetic fields, Interstellar clouds, Circumstellar disks
S0-2 Star, G1- and G2-objects, and Flaring Activity of the Milky Way's Galactic Center Black Hole in 2019. In 2019, the Galactic center black hole Sgr A* produced an unusually high number of bright near-infrared flares, including the brightest-ever detected flare. We propose that this activity was triggered by the near simultaneous infall of material shed by G1 and G2 objects due to their interaction with the background accretion flow. We discuss mechanisms by which S-stars and G-objects shed material, and estimate both the quantity of material and the infall time to reach the black hole.

Keywords: Accretion, Galactic center, Black holes, Astrophysical black holes
Interstellar Detection of 2-cyanocyclopentadiene, C<SUB>5</SUB>H<SUB>5</SUB>CN, a Second Five-membered Ring toward TMC-1. Using radio observations with the Green Bank Telescope, evidence has now been found for a second five-membered ring in the dense cloud Taurus Molecular Cloud-1 (TMC-1). Based on additional observations of an ongoing, large-scale, high-sensitivity spectral line survey (GOTHAM) at centimeter wavelengths toward this source, we have used a combination of spectral stacking, Markov Chain Monte Carlo (MCMC), and matched filtering techniques to detect 2-cyanocyclopentadiene, a low-lying isomer of 1-cyanocyclopentadiene, which was recently discovered there by the same methods. The new observational data also yield a considerably improved detection significance for the more stable isomer and evidence for several individual transitions between 23-32 GHz. Through our MCMC analysis, we derive cospatial, total column densities of 8.3 × 1011 and 1.9 × 1011 cm-2 for 1- and 2-cyanocyclopentadiene, respectively, corresponding to a ratio of ∼4.4 favoring the former. The derived abundance ratios point toward a common formation pathway—most likely being cyanation of cyclopentadiene by analogy to benzonitrile.

Keywords: Molecular spectroscopy, Astrochemistry
Disk, Corona, Jet Connection in the Intermediate State of MAXI J1820+070 Revealed by NICER Spectral-timing Analysis. We analyze five epochs of Neutron star Interior Composition Explorer (NICER) data of the black hole X-ray binary MAXI J1820+070 during the bright hard-to-soft state transition in its 2018 outburst with both reflection spectroscopy and Fourier-resolved timing analysis. We confirm the previous discovery of reverberation lags in the hard state, and find that the frequency range where the (soft) reverberation lag dominates decreases with the reverberation lag amplitude increasing during the transition, suggesting an increasing X-ray emitting region, possibly due to an expanding corona. By jointly fitting the lag-energy spectra in a number of broad frequency ranges with the reverberation model reltrans, we find the increase in reverberation lag is best described by an increase in the X-ray coronal height. This result, along with the finding that the corona contracts in the hard state, suggests a close relationship between spatial extent of the X-ray corona and the radio jet. We find the corona expansion (as probed by reverberation) precedes a radio flare by ∼5 days, which may suggest that the hard-to-soft transition is marked by the corona expanding vertically and launching a jet knot that propagates along the jet stream at relativistic velocities.

Keywords: Black hole physics, High energy astrophysics, Stellar mass black holes, X-ray transient sources, Low-mass x-ray binary stars
Search for the Stochastic Gravitational-wave Background Induced by Primordial Curvature Perturbations in LIGO's Second Observing Run. Primordial density perturbations in the radiation-dominated era of the early universe are expected to generate stochastic gravitational waves (GWs) due to nonlinear mode coupling. In this Letter, we report on a search for such a stochastic GW background in the data of the two LIGO detectors during their second observing run (O2). We focus on the primordial perturbations in the range of comoving wavenumbers 1016-1018 Mpc-1 for which the stochastic background falls within the detectors' sensitivity band. We do not find any conclusive evidence of this stochastic signal in the data, and thus place the very first GW-based constraints on the amplitude of the power spectrum at these scales. We assume a log-normal shape for the power spectrum and Gaussian statistics for the primordial perturbations, and vary the width of the power spectrum to cover both narrow and broad spectra. Derived upper limits (95%) on the amplitude of the power spectrum are 0.01-0.1. As a byproduct, we are able to infer upper limits on the fraction of the universe's mass in ultralight primordial black holes (MPBH ≃ 10-20-10-19M⊙) at their formation time to be ≲10-25.

Keywords: Cosmology, Gravitational waves
The Parallax Zero-point of Gaia Early Data Release 3 from LAMOST Primary Red Clump Stars. We present an independent examination of the parallax zero-point of the Third Gaia Early Data Release (hereafter EDR3), using the LAMOST primary red clump (PRC) stellar sample. A median parallax offset of around 26 μas, slightly larger than that found by examination of distant quasars, is found for both the five- and six-parameter solutions in EDR3, based on samples of over 63,000 and 2000 PRC stars, respectively. Similar to the previous investigation of Lindegren et al., to which we compare our results, the parallax zero-point exhibits clear dependencies on the G magnitudes, colors, and positions of the objects. Based on our analysis, the zero-point of the revised parallax can be reduced to a few μas, and some significant patterns, e.g., discontinuities with stellar magnitude, can be properly removed. However, relatively large offsets (&gt;10 μas) are still found for the revised parallaxes over different positions on the sky.

Keywords: Red giant clump, Trigonometric parallax, Standard candles, Space astrometry
The Core Mass Function in the Orion Nebula Cluster Region: What Determines the Final Stellar Masses?. Applying dendrogram analysis to the CARMA-NRO C18O (J = 1-0) data having an angular resolution of ∼8″, we identified 692 dense cores in the Orion Nebula Cluster region. Using this core sample, we compare the core and initial stellar mass functions in the same area to quantify the step from cores to stars. About 22% of the identified cores are gravitationally bound. The derived core mass function (CMF) for starless cores has a slope similar to Salpeter's stellar initial mass function (IMF) for the mass range above 1 M⊙, consistent with previous studies. Our CMF has a peak at a subsolar mass of ∼0.1 M⊙, which is comparable to the peak mass of the IMF derived in the same area. We also find that the current star formation rate is consistent with the picture in which stars are born only from self-gravitating starless cores. However, the cores must gain additional gas from the surroundings to reproduce the current IMF (e.g., its slope and peak mass), because the core mass cannot be accreted onto the star with 100% efficiency. Thus, the mass accretion from the surroundings may play a crucial role in determining the final stellar masses of stars.

Keywords: Initial mass function, CO line emission, Molecular clouds, Star formation, Interstellar medium, Radio observatories, Protostars
Early Science with the Large Millimeter Telescope: Constraining the Gas Fraction of a Compact Quiescent Galaxy at z = 1.883. We present constraints on the dust continuum flux and inferred gas content of a gravitationally lensed massive quiescent galaxy at z = 1.883 ± 0.001 using AzTEC 1.1 mm imaging with the Large Millimeter Telescope. MRG-S0851 appears to be a prototypical massive compact quiescent galaxy, but evidence suggests that it experienced a centrally concentrated rejuvenation event in the last 100 Myr. This galaxy is undetected in the AzTEC image but we calculate an upper limit on the millimeter flux and use this to estimate the H2 mass limit via an empirically calibrated relation that assumes a constant molecular-gas-to-dust ratio of 150. We constrain the 3σ upper limit of the H2 fraction from the dust continuum in MRG-S0851 to be ${M}_{{{\rm{H}}}_{2}}/{M}_{\star }\leqslant 6.8 \% $ . MRG-S0851 has a low gas fraction limit with a moderately low sSFR owing to the recent rejuvenation episode, which together result in a relatively short depletion time of &lt;0.6 Gyr if no further H2 gas is accreted. Empirical and analytical models both predict that we should have detected molecular gas in MRG-S0851, especially given the rejuvenation episode; this suggests that cold gas and/or dust is rapidly depleted in at least some early quiescent galaxies.

Keywords: Extragalactic astronomy, Galaxy quenching, Quenched galaxies, Galaxy evolution
Climate Change of over 20 °C Induced by Continental Movement on a Synchronously Rotating Exoplanet. It is generally believed that the addition of continents cools the climate of an aquaplanet with a similar orbit to Earth; this is because continents have a higher surface albedo than oceans. A similar effect has been shown in climate simulations for exoplanets. Here we demonstrate that the influence of a continent on ocean circulation could have a dominative effect on the climate of a synchronously rotating exoplanet compared with the effect of the surface albedo, especially when the rotation of the exoplanet is relatively slow (e.g., the rotational period is 40 Earth days). The global mean surface temperature could vary by more than 26° C, simply by moving a small continent to a different location. The ocean circulation on a synchronously rotating exoplanet is characterized by a strong westerly jet along the equator and one large gyre in each hemisphere. The surface temperature decreases when the equatorial westerly or the western branch of either of the gyres is blocked by a continent or an island arc chain. However, if the continent blocks the eastern branch of the gyre, the equatorial westerly is strengthened and the climate warms. A large number of potentially habitable exoplanets have been found orbiting around M-dwarfs in a tidally locked manner; our results indicate that their climates, as well as their atmospheric chemistry, may deviate from previous estimates if a small continent, or even an island arc chain, is present.

Keywords: Exoplanet dynamics, Extrasolar rocky planets, Ocean planets, Exoplanets, Planetary climates, Habitable planets, Exoplanet atmospheres
First Detection of Hydroxyl Radical Emission from an Exoplanet Atmosphere: High-dispersion Characterization of WASP-33b Using Subaru/IRD. We report the first detection of a hydroxyl radical (OH) emission signature in the planetary atmosphere outside the solar system, in this case, in the dayside of WASP-33b. We analyze high-resolution near-infrared emission spectra of WASP-33b taken using the InfraRed Doppler spectrograph on the 8.2 m Subaru telescope. The telluric and stellar lines are removed using a detrending algorithm, SYSREM. The residuals are then cross-correlated with OH and H2O planetary spectrum templates produced using several different line lists. We check and confirm the accuracy of OH line lists by cross-correlating with the spectrum of GJ 436. As a result, we detect the emission signature of OH at Kp of ${230.9}_{-7.4}^{+6.9}$ km s-1 and vsys of -0.3 ${}_{-5.6}^{+5.3}$ km s-1 with a signal-to-noise ratio (S/N) of 5.4 and a significance of 5.5σ. Additionally, we marginally detect H2O emission in the H-band with an S/N of 4.0 and a significance of 5.2σ using the POKAZATEL line list. However, no significant signal is detected using the HITEMP 2010, which might be due to differences in line positions and strengths, as well as the incompleteness of the line lists. Nonetheless, this marginal detection is consistent with the prediction that H2O is mostly thermally dissociated in the upper atmosphere of the ultra-hot Jupiters. Therefore, along with CO, OH is expected to be one of the most abundant O-bearing molecules in the dayside atmosphere of ultra-hot Jupiters and should be considered when studying their atmospheres. * Based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

Keywords: High resolution spectroscopy, Exoplanet atmospheric composition , Exoplanet atmospheres