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Keyword list: ['star formation', 'star-forming', 'molecular cloud', 'interstellar medium', 'cloud', 'clump', 'core', 'filament', 'atomic gas', 'N-PDF']

Excluded: ['galaxies', 'galaxy cluster', ' AGN ']

Today: 12papers

Constraining $\gamma$-ray dissipation site in gravitationally lensed quasar -- PKS 1830$-$211

• Authors: Sushmita Agarwa, Amit Shukla, Pranjali Sharma

• Subjects: Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

• Arxiv link: https://arxiv.org/abs/2501.04775

• Pdf link: https://arxiv.org/pdf/2501.04775

• Abstract Variable $\gamma$-ray flares upto minute timescales reflect extreme particle acceleration sites. However, for high-redshift blazars, the detection of such rapid variations remains limited by current telescope sensitivities. Gravitationally lensed blazars serve as powerful tools to probe $\gamma$-ray production zones in distant sources, with time delays between lensed signals providing crucial insights into the spatial distribution of emission regions relative to the lens's mass-weighted center. We have utilized 15 years of Fermi-LAT $\gamma$-ray data from direction of PKS 1830$-$211 to understand the origin of flaring high-energy production zone at varying flux states. To efficiently estimate the (lensed) time delay, we used a machine learning-based tool - the Gaussian Process regression algorithm, in addition to - Autocorrelation function and Double power spectrum. We found a consistent time delay across all flaring activity states, indicating a similar location for the $\gamma$-ray emission zone, possibly within the radio core. The estimated time delay of approximately 20 days for the five flaring epochs was significantly shorter than previously estimated radio delays. This suggests that the $\gamma$-ray emission zone is closer to the central engine, in contrast to the radio emission zone, which is expected to be much farther away. A linear relationship between lag and magnification has been observed in the identified source and echo flares. Our results suggest that the $\gamma$-ray emission zone originates from similar regions away from the site of radio dissipation.

Detectability of Emission from Exoplanet Outflows Calculated by pyTPCI, a New 1D Radiation-Hydrodynamic Code

• Authors: Riley Rosener, Michael Zhang, Jacob L. Bean

• Subjects: Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)

• Arxiv link: https://arxiv.org/abs/2501.04834

• Pdf link: https://arxiv.org/pdf/2501.04834

• Abstract Photoevaporation in exoplanet atmospheres is thought to contribute to the shaping of the small planet radius valley. Escaping atmospheres have been detected in transmission across a variety of exoplanet types, from hot Jupiters to mini-Neptunes. However, no work has yet considered whether outflows might also be detectable in emission. We introduce pyTPCI, a new, open-source self-consistent 1D radiative-hydrodynamics code that is an improved version of The PLUTO-CLOUDY Interface. We use pyTPCI to model seven exoplanets (HD 189733b, HD 209458b, WASP-69b, WASP-107b, TOI-1430b, TOI-560b, and HAT-P-32b) at varying metallicities and compute their emission spectra to investigate their detectability across a variety of spectral lines. We calculate the eclipse depths and signal-to-noise ratios (SNR) of these lines for a 10m class telescope with a high-resolution spectrograph, taking into account appropriate line broadening mechanisms. We show that the most detectable spectral lines tend to be the 589 nm Na I doublet and the 1083 nm metastable helium triplet. Halpha and Mg I 457 nm are moderately strong for some planets at some metallicities, but they are almost always optically thin, so some of their emission may not be from the outflow. The planet with the highest-flux, highest-eclipse-depth, and highest-SNR lines is HD 189733b, with a Na I eclipse depth of 410 ppm and SNR of 2.4 per eclipse, and a He* eclipse depth of 170 ppm and SNR of 1.3. These signals would be marginally detectable with Keck if 3-10 eclipses were observed, assuming (over-optimistically) photon limited observations.

Gravitational waves from r-mode oscillations of stochastically accreting neutron stars

• Authors: Wenhao Dong, Andrew Melatos

• Subjects: Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); General Relativity and Quantum Cosmology (gr-qc)

• Arxiv link: https://arxiv.org/abs/2501.04968

• Pdf link: https://arxiv.org/pdf/2501.04968

• Abstract $r$-mode oscillations in rotating neutron stars are a source of continuous gravitational radiation. We investigate the excitation of $r$-modes by the mechanical impact on the neutron star surface of stochastically accreted clumps of matter, assuming that the Chandrasekhar-Friedman-Schutz instability is not triggered. The star is idealised as a slowly-rotating, unmagnetised, one-component fluid with a barotropic equation of state in Newtonian gravity. It is found that the $r$-mode amplitude depends weakly on the equation of state but sensitively on the rotation frequency $\nu_{\rm s}$. The gravitational wave strain implicitly depends on the equation of state through the damping timescale. The root-mean-square strain is $h_{\rm rms} \approx 10^{-35} (\nu_{\rm s}/ 10 {\rm Hz})^{2} (R_/10 {\rm km})^2 (\Delta t_{\rm acc}/1 {\rm yr})^{1/2} (f_{\rm acc}/1 {\rm kHz})^{-1/2} (\dot{M}/10^{-8} \text{M}{\odot} \text{yr}^{-1}) (v/0.4c) (d/1 {\rm kpc})^{-1}$, which is comparable to the strain from $g$-, $p$- and $f$-modes excited by stochastic accretion, where $R$ is the radius of the star, $\Delta t_{\rm acc}$ is the uninterrupted duration of an accretion episode, $f_{\rm acc}$ is the mean clump impact frequency, $\dot{M}$ is the accretion rate, $v$ is the impact speed, and $d$ is the distance of the star from the Earth. An observational test is proposed, based on the temporal autocorrelation function of the gravitational wave signal, to discern whether the Chandrasekhar-Friedman-Schutz instability switches on and coexists with impact-excited $r$-modes before or during a gravitational wave observation.

Multiple Populations of the Large Magellanic Cloud Globular Cluster NGC 2257: No Major Environmental Effect on the Formation of Multiple Populations of the Old Globular Clusters in Large Magellanic Cloud

• Authors: Jae-Woo Lee, Tae-Hyeong Kim, Hak-Sub Kim, Hyun-Il Sung, Hwihyun Kim, Francesco Di Mille

• Subjects: Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

• Arxiv link: https://arxiv.org/abs/2501.04979

• Pdf link: https://arxiv.org/pdf/2501.04979

• Abstract How the environment of the host galaxy affects the formation of multiple populations (MPs) in globular clusters (GCs) is one of the outstanding questions in the near-field cosmology. To understand the true nature of the old GC MPs in the Large Magellanic Cloud (LMC), we study the Ca--CN--CH photometry of the old metal-poor LMC GC NGC 2257. We find the predominantly FG-dominated populational number ratio of $n$(FG):$n$(SG) = 61:39($\pm$4), where the FG and SG denote the first and second generations. Both the FG and SG have similar cumulative radial distributions, consistent with the idea that NGC 2257 is dynamically old. We obtain [Fe/H] = $-$1.78$\pm$0.00 dex($\sigma$=0.05 dex) and our metallicity is $\sim$0.2 dex larger than that from the high-resolution spectroscopy by other, due to their significantly lower temperatures by $\sim$ $-$200 K. The NGC 2257 FG shows a somewhat larger metallicity variation than the SG, the first detection of such phenomenon in an old LMC GC, similar to Galactic GCs with MPs, strongly suggesting that it is a general characteristic of GCs with MPs. Interestingly, the NGC 2257 SG does not show a helium enhancement compared to the FG. Our results for the Galactic normal GCs exhibit that the degree of carbon and nitrogen variations are tightly correlated with the GC mass, while NGC 2257 exhibits slightly smaller variations for its mass. We show that old LMC GCs follow the same trends as the Galactic normal GCs in the $\Delta$W${\rm CF336W,F438W,F814W}$, $N{\rm FG}/N_{\rm tot}$, and $\log M/M_{\rm \odot}$ domains. Our result indicates that the environment of the host galaxy did not play a major role in the formation and evolution of GC MPs.

ALMA Observations of Peculiar Embedded Icy Objects

• Authors: Takashi Shimonishi, Takashi Onaka, Itsuki Sakon

• Subjects: Subjects: Astrophysics of Galaxies (astro-ph.GA); Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

• Arxiv link: https://arxiv.org/abs/2501.05008

• Pdf link: https://arxiv.org/pdf/2501.05008

• Abstract We report the results of molecular line observations with the Atacama Large Millimeter/submillimeter Array (ALMA) towards two peculiar icy objects, which were discovered serendipitously by infrared spectroscopic survey of the Galactic plane with the AKARI satellite. Previous infrared observations have reported that both objects show deep ice and dust absorption features that are often seen in embedded young stellar objects (YSOs) or background stars sitting behind dense clouds, however, they are located neither in known star-forming regions nor in known dense clouds. Their infrared spectral energy distributions (SEDs) show a peak around 5 micron, which are incompatible with existing SED models of typical embedded YSOs. The present ALMA observations have detected compact emission of CO(3-2) and SiO(8-7) at the positions of the icy objects. The observed large column ratios of gas-phase SiO/CO (~10^-3) in both objects, as well as their broad line widths (8-14 km/s), imply that they are associated with shocked gas. Although a large dust extinction (Av ~100 mag) is expected from their deep dust/ice absorption, no dust continuum emission is detected, which would suggest a large beam dilution effect due to their compact source sizes. Their systemic velocities are clearly separated from the surrounding CO clouds, suggesting that they are isolated. The characteristics of their SEDs, the presence of deep dust/ice absorption features, compact source size, and SiO-dominated broad molecular line emission, cannot easily be accounted for by any of known interstellar ice-absorption sources. They may represent a previously unknown type of isolated icy objects.

Planetary Nebulae of the Large Magellanic Cloud II: the connection with the progenitors' properties

• Authors: P. Ventura, S. Tosi, D. A. García-Hernández, F. Dell'Agli, D. Kamath, L. Stanghellini, S. Bianchi, M. Tailo, M. A. Gómez-Muñoz

• Subjects: Subjects: Solar and Stellar Astrophysics (astro-ph.SR); Astrophysics of Galaxies (astro-ph.GA)

• Arxiv link: https://arxiv.org/abs/2501.05013

• Pdf link: https://arxiv.org/pdf/2501.05013

• Abstract The study of planetary nebulae (PNe) offers the opportunity of evaluating the efficiency of the dust production mechanism during the very late asymptotic giant branch (AGB) phases. We study the relationship between the properties of PNe, particularly the gas and dust content, with the mass and metallicity of the progenitor stars, to understand how dust production works in the late AGB phases, and to shed new light on the physical processes occurring to the stars and the material in their surroundings since the departure from the AGB until the PN phase. We consider a sample of 9 PNe in the Large Magellanic Cloud, 7 out of which characterized by the presence of carbonaceous dust, the remaining 2 with silicates. For these stars the masses and the metallicity of the progenitor stars were estimated. We combine results from stellar evolution and dust formation modelling with those coming from the analysis of the spectral energy distribution, to find the relation between the dust and gas mass of the PNe considered and the The physical properties of carbon-rich PNe are influenced by the mass of the progenitor star. Specifically, the dust-to-gas ratio in the nebula increases from 5x10^{-4}to 6x10^{-3} as the progenitor star's mass increases from approximately 0.9Msun to 2Msun. This change is partly influenced by the effective temperature of the PNe, and it occurs because higher-mass carbon stars are more efficient at producing dust. Consequently, as the progenitor's mass increases, the gas mass of the PNe decreases, since the larger amounts of dust lead to greater effects from radiation pressure, which pushes the gas outwards. No meaningful conclusions can be drawn by the study of the PNe with silicate-type dust, because the sub-sample is made up of 2 PNe only, one of which is almost dust-free.

The ESO SupJup Survey V: Exploring Atmospheric Variability and Orbit of the Super-Jupiter AB Pictoris b with CRIRES+

• Authors: Siddharth Gandhi, Sam de Regt, Ignas Snellen, Paulina Palma-Bifani, Idriss Abdoulwahab, Gaël Chauvin, Darío González Picos, Yapeng Zhang, Rico Landman, Tomas Stolker, Aurora Kesseli, Willeke Mulder, Antoine Chomez, Anne-Marie Lagrange, Alice Zurlo

• Subjects: Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

• Arxiv link: https://arxiv.org/abs/2501.05114

• Pdf link: https://arxiv.org/pdf/2501.05114

• Abstract A growing number of directly-imaged companions have been recently characterised, with robust constraints on carbon-to-oxygen ratios and even isotopic ratios. Many companions and isolated targets have also shown spectral variability. In this work we observed the super-Jupiter ABPictorisb across four consecutive nights using VLT/CRIRES+ as part of the ESO SupJup survey, exploring how the constraints on chemical composition and temperature profile change over time using spectral line shape variations between nights. We performed atmospheric retrievals of the high-resolution observations and found broadly consistent results across all four nights, but there were differences for some parameters. We clearly detect H$_2$O, $^{12}$CO and $^{13}$CO in each night, but abundances varied by $\sim2\sigma$, which was correlated to the deep atmosphere temperature profiles. We also found differences in the $^{12}$C$/^{13}$C ratios in each night by up to $\sim3\sigma$, which seemed to be correlated with the cloud deck pressure. Our combined retrieval simultaneously analysing all nights together constrained broadly the average of each night individually, with the C/O$=0.59\pm0.01$, consistent with solar composition, and $^{12}$C$/^{13}$C~$ = 102\pm8$, slightly higher than the ISM and Solar System values. We also find a low projected rotational velocity, suggesting that ABPictorisb is either intrinsically a slow rotator due to its young age or that the spin axis is observed pole-on with a $\sim90^\circ$ misalignment with its orbit inclination. Future observations will be able to further explore the variability and orbit of ABPictorisb as well as for other companions.

Detection of thioacetaldehyde (CH3CHS) in TMC-1: sulfur-oxygen differentiation along the hydrogenation sequence

• Authors: M. Agundez, G. Molpeceres, C. Cabezas, N. Marcelino, B. Tercero, R. Fuentetaja, P. de Vicente, J. Cernicharo

• Subjects: Subjects: Astrophysics of Galaxies (astro-ph.GA)

• Arxiv link: https://arxiv.org/abs/2501.05125

• Pdf link: https://arxiv.org/pdf/2501.05125

• Abstract In recent years the chemistry of sulfur in the interstellar medium has experienced a renewed interest due to the detection of a large variety of molecules containing sulfur. Here we report the first identification in space of a new S-bearing molecule, thioacetaldehyde (CH3CHS), which is the sulfur counterpart of acetaldehyde (CH3CHO). The astronomical observations are part of QUIJOTE, a Yebes 40m Q band line survey of the cold dense cloud TMC-1. We detected seven individual lines corresponding to A and E components of the four most favorable rotational transitions of CH3CHS covered in the Q band (31.0-50.3 GHz). Assuming a rotational temperature of 9 K, we derive a column density of 9.8e10 cm-2 for CH3CHS, which implies that it is 36 times less abundant than its oxygen counterpart CH3CHO. By comparing the column densities of the O- and S-bearing molecules detected in TMC-1, we find that as molecules increase their degree of hydrogenation, sulfur-bearing molecules become less abundant compared to their oxygen analog. That is, hydrogenation seems to be less favored for S-bearing molecules than for O-bearing ones in cold sources like TMC-1. We explored potential formation pathways to CH3CHS and implemented them into a chemical model, which however underestimates by several orders of magnitude the observed abundance of thioacetaldehyde. Quantum chemical calculations carried out for one of the potential formation pathways, the S + C2H5 reaction, indicate that formation of CH3CHS is only a minor channel in this reaction.

Impact of photoevaporative winds in chemical models of externally irradiated protoplanetary disks

• Authors: Luke Keyte, Thomas J. Haworth

• Subjects: Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR)

• Arxiv link: https://arxiv.org/abs/2501.05172

• Pdf link: https://arxiv.org/pdf/2501.05172

• Abstract Most stars form in dense clusters within high-mass star-forming regions, where protoplanetary disks may be exposed to intense UV radiation from nearby massive stars. While previous studies have typically focused on isolated sources in low-mass regions, recent observational campaigns have started to probe the chemistry of irradiated disks in unprecedented detail. Interpreting this data requires complex chemical models, yet few studies have examined these disks' chemistry, and none have incorporated the photoevaporative wind launched by external UV fields into their physical structure. In this study, we post-process radiation hydrodynamics simulations of externally irradiated protoplanetary disks using the thermochemical code DALI, comparing models with and without the wind to assess its impact on disk chemistry. Results show that UV radiation is rapidly attenuated by the disk in both cases. However, thermal re-emission from the wind at longer wavelengths enhances disk heating, increasing the gas-phase abundances of some key volatiles. Synthetic line fluxes vary by orders of magnitude between wind and windless models, primarily due to emission from the wind itself rather than abundance variations within the disk. Our findings demonstrate that the photoevaporative wind significantly influences the physical and chemical structure, and observational characteristics, of externally irradiated disks. We conclude that incorporating the wind into chemical models is essential for accurately predicting chemical abundances, interpreting observations, and ultimately understanding planet formation in these common yet complex environments.

Exploring the non-thermal physics behind the pulsar wind nebula PSR J2030+4415 through radio observations

• Authors: J.M. Paredes, P. Benaglia, V. Bosch-Ramon, A.Tej, A. Saha, J. Martí, P. Bordas

• Subjects: Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

• Arxiv link: https://arxiv.org/abs/2501.05284

• Pdf link: https://arxiv.org/pdf/2501.05284

• Abstract PSR J2030+4415 is a gamma-ray pulsar with an X-ray pulsar wind nebula elongated along the north-south direction. The system shows a prominent X-ray filament oriented at an angle of 130° to the nebula axis. To improve our understanding of the non-thermal processes occurring in the pulsar wind nebula, we attempted to determine the possible existence of a radio counterpart, study its morphology, and obtain restrictive upper limits of the pulsar and filament emission at radio wavelengths. We performed observations of the pulsar PSR J2030+4415 and its surroundings with the upgraded Giant Metrewave Radio Telescope (uGMRT) at two frequency bands, and put the results in context with findings at other wavelengths. We obtained radio images at 736 and 1274 MHz that reveal a structure trailing the pulsar, with a morphology overlapping the X-ray nebula. This radio structure is the radio counterpart of the X-ray pulsar wind nebula. The derived spectral index along this structure shows spatial variation. There are no hints of the pulsar and the filament at any of the explored radio frequencies, but we obtained restrictive upper limits. A physical scenario that combines the radio and the X-ray observations, and consistent with IR data, of the nebula and the filament is presented. We propose that particle acceleration occurs in the nebula tail due to the presence of a re-collimation shock, and the highest energy particles gradually escape from it through energy-dependent diffusion. We also find a lower limit in the energy of the particles escaping along the X-ray filament of ~GeV.

Martian atmospheric disturbances from orbital images and surface pressure at Jezero Crater, Mars, during Martian Year 36

• Authors: A. Sánchez-Lavega, E. Larsen, T. del Río-Gaztelurrrutia, J. Hernández-Bernal, I. Ordóñez-Etxebarría, R. Hueso, B. Tanguy, M. Lemmon, M. de la Torre Juarez, G. M. Martínez, A. Munguira, J. A. Rodríguez-Manfredi, A.-M. Harri, J. Pla-García, D. Toledo, C. Newman

• Subjects: Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

• Arxiv link: https://arxiv.org/abs/2501.05337

• Pdf link: https://arxiv.org/pdf/2501.05337

• Abstract We present a study of atmospheric disturbances at Jezero Crater, Mars, using ground-based measurements of surface pressure by the Perseverance rover in combination with orbital images from the Mars Express and Mars Reconnaissance Orbiter missions. The study starts at Ls $\sim$ 13.3° in MY36 (March 6th, 2021) and extends up to Ls $\sim$ 30.3° in MY37 (February 28th, 2023). We focus on the characterization of the major atmospheric phenomena at synoptic and planetary-scales. These are the thermal tides (measured up to the sixth component), long-period pressure oscillations (periods > 1 sol), the Aphelion Cloud Belt, and the occasional development of regional dust storms over Jezero. We present the seasonal evolution of the amplitudes and phases of the thermal tides and their relation with the atmospheric dust content (optical depth). Three regional dust storms and one polar storm extending over Jezero produced an increase in the diurnal and semidiurnal amplitudes but resulted in inverse responses in their phases. We show that the primary regular wave activity is due to baroclinic disturbances with periods of 2-4 sols and amplitudes $\sim$ 1-15 Pa increasing with dust content, in good agreement with theoretical predictions by model calculations. The spacecraft images show a number of arc-shaped, spiral and irregular cyclonic vortices, traced by dust and clouds at the edge of the North Polar Cap, that could be behind some of the pressure oscillations measured at Jezero.

Harvesting primordial black holes from stochastic trees with $\texttt{FOREST}$

• Authors: Chiara Animali, Pierre Auclair, Baptiste Blachier, Vincent Vennin

• Subjects: Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

• Arxiv link: https://arxiv.org/abs/2501.05371

• Pdf link: https://arxiv.org/pdf/2501.05371

• Abstract We introduce a novel framework to implement stochastic inflation on stochastic trees, modelling the inflationary expansion as a branching process. Combined with the $\delta N$ formalism, this allows us to generate real-space maps of the curvature perturbation that fully capture quantum diffusion and its non-perturbative backreaction during inflation. Unlike lattice methods, trees do not proceed on a fixed background since new spacetime units emerge dynamically as trees unfold, naturally incorporating metric fluctuations. The recursive structure of stochastic trees also offers remarkable numerical efficiency, and we develop the FOrtran Recursive Exploration of Stochastic Trees ($\texttt{FOREST}$) tool and demonstrate its performance. We show how primordial black holes blossom at unbalanced nodes of the trees, and how their mass distribution can be obtained while automatically accounting for the "cloud-in-cloud" effect. In the "quantum-well" toy model, we find broad mass distributions, with mild power laws terminated by exponential tails. We finally compare our results with existing approximations in the literature and discuss several prospects.

by olozhika (Xing Yuchen).

2025-01-10