Continuum Emission Research Articles

Uncovering the structure and kinematics of the ionized core of M\,2-9 with ALMA

We present interferometric observations at 1 and 3\,mm with the Atacama Large Millimeter Array (ALMA) of the free-free continuum and millimeter(mm)-wavelength recombination line (mRRL) emission of the ionized core (within lsim 130\,au) of the young planetary nebula (PN) candidate M\,2-9. These inner regions are concealed in the vast majority of similar objects. A spectral index for the mm-to-centimeter(cm) continuum of sim 0.9 indicates predominantly free-free emission from an ionized wind, with a minor contribution from warm dust. The mm continuum emission in M\,2-9 reveals an elongated structure along the main symmetry axis of the large-scale bipolar nebula with a C-shaped curvature surrounded by a broad-waisted component. This structure is consistent with an ionized, bent jet and a perpendicular compact dusty disk. The presence of a compact equatorial disk (of radius sim 50\,au) is also supported by redshifted CO and absorption profiles observed from the base of the receding northern lobe against the compact background continuum. The redshift observed in the CO absorption profiles likely signifies gas infall movements from the disk toward a central source. The mRRLs exhibit velocity gradients along the axis, implying systematic expansion in the C-shaped bipolar outflow. The highest expansion velocities (sim 80\ are found in two diagonally opposed compact regions along the axis, referred to as the high-velocity spots or shells (HVSs), indicating either rapid wind acceleration or shocks at radial distances of sim 0 (sim 15-25\,au) from the center. A subtle velocity gradient perpendicular to the lobes is also found, suggesting rotation. Our ALMA observations detect increased brightness and broadness in the mRRLs compared to previously observed profiles, implying variations in wind kinematics and physical conditions on timescales of less than two years, which is in agreement with the extremely short kinematic ages (lsim 0.5-1\,yr) derived from observed velocity gradients in the compact ionized wind. Radiative transfer modeling indicates an average electron temperature of sim 15000\,K and reveals a nonuniform density structure within the ionized wind with electron densities ranging from to 10$^8$\ These results potentially reflect a complex bipolar structure resulting from the interaction of a tenuous companion-launched jet and the dense wind of the primary star.

Sulfur-bearing molecules in a sample of early star-forming cores

The sulfur content in dense molecular regions is highly depleted in comparison to diffuse clouds. The reason for this phenomenon is unclear, and it is therefore necessary to carry out observational studies of sulfur-bearing species toward dense regions, mainly in early evolution stages. In this context, the analysis of sulfur-bearing molecules in a large sample of dense starless molecular cores is of great importance to help us uncover the early sulfur chemistry in these regions. From the Atacama Large Millimeter Array (ALMA) data archive, we selected a project in Band 7 (275--373 GHz), which contains the emission of several sulfur-bearing species. The observations were performed toward a sample of 37 dense cores that are embedded in the most massive infrared-quiet molecular clumps from the ATLASGAL survey. The lines of 34SO, SO$_ $, NS, SO, SO$^ $, and H$_ $CS were analyzed, and the column densities of each molecular species were obtained. Based on the continuum emission and two CH$_ $OH lines, the 37 cores were characterized in density and temperature, and the corresponding H$_ $ column densities were derived. The abundances of these sulfur-bearing species were derived and studied. We find that the abundances of the analyzed sulfur-bearing species increase with increasing gas temperature. Based on the correlation between abundances and temperature, we suggest that the chemistry involved in the formation of each of the analyzed molecules may similarly depend on T$_ k $ in the range 20 to 100 K. Additionally, we find that the comparisons among abundances are highly correlated in general. Taking into account that this correlation decreases in more evolved sources, we suggest that the sulfur-bearing species we analyzed have a similar chemical origin. Our observational results show that the X(SO$_ $)/X(SO) ratio can be used as a chemical clock of molecular cores. Based on the line widths of the molecular lines, we point out that molecules with an oxygen content (34SO, SO$_ $, SO, and SO$^ $) may be associated with warmer and more turbulent gas than the other molecules. H$_ $CS and NS are associated with more quiescent gas, probably in the external envelopes of the cores, which trace similar physical and chemical conditions. We complement recent similar works done toward more evolved sources with a large sample of sources, but also provide quantitative information about abundances that might be useful in chemical models for explaining the sulfur chemistry in the interstellar medium.

Dust mass in protoplanetary disks with porous dust opacities

Atacama Large Millimeter/submillimeter Array surveys have suggested that protoplanetary disks are not massive enough to form the known exoplanet population, based on the assumption that the millimeter continuum emission is optically thin. In this work, we investigate how the mass determination is influenced when the porosity of dust grains is considered in radiative transfer models. The results show that disks with porous dust opacities yield similar dust temperatures, but systematically lower millimeter fluxes, as compared to disks that incorporate compact dust grains. Moreover, we have recalibrated the relation between dust temperature and stellar luminosity for a wide range of stellar parameters. We also calculated the dust masses of a large sample of disks using the traditionally analytic approach. The median dust mass from our calculation is about six times higher than the literature result, and this is mostly driven by the different opacities of porous and compact grains. A comparison of the cumulative distribution function between disk dust masses and exoplanet masses shows that the median exoplanet mass is about two times lower than the median dust mass when grains are assumed to be porous and there are no exoplanetary systems with masses higher than the most massive disks. Our analysis suggests that adopting porous dust opacities may alleviate the mass budget problem for planet formation. As an example illustrating the combined effects of optical depth and porous dust opacities on the mass estimation, we conducted new IRAM/NIKA-2 observations toward the IRAS\,04370+2559 disk and performed a detailed radiative transfer modeling of the spectral energy distribution (SED). The best-fit dust mass is roughly 100 times higher than the value given by a traditionally analytic calculation. Future spatially resolved observations at various wavelengths are required to better constrain the dust mass.

ALMA and GMRT Studies of Dust Continuum Emission and Spectral Lines Toward Oort Cloud Comet C/2022 E3 (ZTF)

Abstract The atomic and molecular compounds of cometary ices serve as valuable knowledge into the chemical and physical properties of the outer solar nebula, where comets are formed. From the cometary atmospheres, the atoms and gas-phase molecules arise mainly in three ways: (i) the outgassing from the nucleus, (ii) the photochemical process, and (iii) the sublimation of icy grains from the nucleus. In this paper, we present the radio and millimeter wavelength observation results of Oort cloud non-periodic comet C/2022 E3 (ZTF) using the Giant Metrewave Radio Telescope (GMRT) band L and the Atacama Large Millimeter/Submillimeter Array (ALMA) band 6. We do not detect continuum emissions and an emission line of atomic hydrogen (HI) at rest frequency 1420 MHz from this comet using the GMRT. Based on ALMA observations, we detect the dust continuum emission and rotational emission lines of methanol (CH3OH) from comet C/2022 E3 (ZTF). From the dust continuum emission, the activity of dust production (Afρ) of comet ZTF is 2280±50 cm. Based on LTE spectral modelling, the column density and excitation temperature of CH3OH towards C/2022 E3 (ZTF) are (4.50±0.25)×10^{14} cm^{−2} and 70±3 K. The integrated emission maps show that CH3OH was emitted from the coma region of the comet. The production rate of CH3OH towards C/2022 E3 (ZTF) is (7.32±0.64)×10^{26} molecules s^{−1}. The fractional abundance of CH3OH with respect to H2O in the coma of the comet is 1.52%. We also compare our derived abundance of CH3OH with the existence modelled value, and we see the observed and modelled values are nearly similar. We claim that CH3OH is formed via the subsequential hydrogenation of formaldehyde (H2CO) on the grain surface of comet C/2022 E3 (ZTF).

Medium Bands, Mega Science: A JWST/NIRCam Medium-band Imaging Survey of A2744

In this paper, we describe the “Medium Bands, Mega Science” JWST Cycle 2 survey (JWST-GO-4111) and demonstrate the power of these data to reveal both the spatially integrated and spatially resolved properties of galaxies from the local Universe to the era of cosmic dawn. Executed in 2023 November, MegaScience obtained ∼30 arcmin2 of deep multiband NIRCam imaging centered on the z ∼ 0.3 A2744 cluster, including 11 medium-band filters and the two shortest-wavelength broadband filters, F070W and F090W. Together, MegaScience and the UNCOVER Cycle 1 treasury program provide a complete set of deep (∼28–30 magAB) images in all NIRCam medium- and broadband filters. This unique data set allows us to precisely constrain photometric redshifts, map stellar populations and dust attenuation for large samples of distant galaxies, and examine the connection between galaxy structures and formation histories. MegaScience also includes ∼17 arcmin2 of NIRISS parallel imaging in two broadband and four medium-band filters from 0.9 to 4.8 μm, expanding the footprint where robust spectral energy distribution (SED) fitting is possible. We provide example SEDs and multiband cutouts at a variety of redshifts, and use a catalog of JWST spectroscopic redshifts to show that MegaScience improves both the scatter and catastrophic outlier rate of photometric redshifts by factors of 2–3. Additionally, we demonstrate the spatially resolved science enabled by MegaScience by presenting maps of the [O iii] line emission and continuum emission in three spectroscopically confirmed z > 6 galaxies. We show that line emission in reionization-era galaxies can be clumpy, extended, and spatially offset from continuum emission, implying that galaxy assembly histories are complex even at these early epochs. We publicly release fully reduced mosaics and photometric catalogs for both the NIRCam primary and NIRISS parallel fields (jwst-uncover.github.io/megascience).

Temperature measurement method with line and continuum emissions in Ar-N2 DC arc

This study discusses a technique for accurate temperature measurement of thermal plasmas with a high-speed camera. The temperature of thermal plasmas is an important parameter for plasma processes. High-speed cameras are useful to measure plasma temperatures in two dimensions. Measurements of plasma emission with a high-speed camera and band-pass filter provide only the spectral intensity of the entire transmitted wavelength range. Temperature measurements with high-speed cameras by the Boltzmann plot method or Fowler⎯Milne method are less accurate. Theoretical consideration of the line and continuum emissions has improved the accuracy of plasma temperature measurement. The measurement target was a free-burning arc in an argon and nitrogen atmosphere. Temperature errors were estimated based on the deviation from the true emission coefficient. The calculation and measurement errors were discussed as the factors of the deviation. Error estimation provides important insight into the selection of the measurement wavelength.

AGN STORM 2. X. The Origin of the Interband Continuum Delays in Mrk 817* *Based in part on observations associated with program GO-16196 made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

The local (z = 0.0315) active galactic nucleus (AGN) Mrk 817 was monitored over more than 500 days with space-borne and ground-based instruments as part of a large international campaign, AGN STORM 2. Here, we present a comprehensive analysis of the broadband continuum variations using detailed modeling of the broad line region (BLR), several types of disk winds classified by their optical depth, and new numerical simulations. We find that diffuse continuum (DC) emission, with additional contributions from strong and broad emission lines, can explain the continuum lags observed in this source during high- and low-luminosity phases. Disk illumination by the variable X-ray corona contributes only a small fraction of the observed continuum lags. Our BLR models assume radiation-pressure-confined clouds distributed over a distance of 2–122 light days. We present calculated mean emissivity radii of many emission lines, and DC emission, and suggest a simple, transfer-function-dependent method that ties them to cross-correlation lag determinations. We do not find clear indications for large-optical-depth winds, but identify the signature of lower-column-density winds. In particular, we associate the shortest observed continuum lags with a combination of τ(1 Ryd) ≈ 2 wind and a partly shielded BLR. Even smaller optical depth winds may be associated with X-ray absorption features and with noticeable variations in the widths and lags of several high-ionization lines like He ii and C iv. Finally, we demonstrate the effect of torus dust emission on the observed lags in the i and z bands.

An X-Ray Shell Reveals the Supernova Explosion for Galactic Microquasar SS 433

How black holes are formed remains an open and fundamental question in astrophysics. Despite theoretical predictions, it lacks observations to understand whether the black hole formation experiences a supernova explosion. Here we report the discovery of an X-ray shell north of the Galactic microquasar SS 433 harboring a stellar-mass black hole spatially associated with radio continuum and polarization emissions and an H i cloud. Its spectrum can be reproduced by a 1 keV underionized plasma, from which the shell is inferred to have been created by a supernova explosion 20–30 kyr ago, and its properties constitute evidence for canonical supernova explosions to create some black holes. Our analysis precludes other possible origins including heated by jets or blown by disk winds. According to the lower mass limit of the compact object in SS 433, we roughly deduced that the progenitor should be more massive than 25 M ⊙. The existence of such a young remnant in SS 433 can also lead to new insights into the supercritical accretion in young microquasars and the γ-ray emission of this system. The fallback ejecta may provide accretion materials within tens of thousands of years, while the shock of the supernova remnant may play a crucial role in the cosmic-ray (re)acceleration.

Electron temperature characterization of H2 processing plasma by optical emission spectroscopy

Optical emission spectroscopy of hydrogen (H2) plasma is performed to characterize the electron temperature, T e . The H2 Fulcher band emission and radiative dissociation continuum are measured, where the Fulcher band emission is recognized to be T e -sensitive, compared with the dissociation continuum. With this T e -sensitive nature, a simple way of determining T e is proposed, specifically using the intensity ratio of the Fulcher band emission to dissociation continuum. The T e determination is demonstrated for H2 processing plasmas generated by capacitively coupled discharges at different gas pressures.

An interferometric search for SiO maser emission in planetary nebulae

Maser emission of SiO, H$_2$O, and OH is widespread in asymptotic giant branch (AGB) stars with oxygen- (O-) rich envelopes. This emission quickly disappears during the post-AGB phase and is extremely rare in planetary nebulae (PNe). So far, only eight PNe have been confirmed to show OH and/or H$_2$O maser emission, and none have ever been found to show SiO maser emission. We intend to obtain the first detection of a SiO maser from a PN. Such a detection would provide us with a useful tool to probe mass loss in PNe at a scales of a few AU from the central star, much shorter than the scales traced by H$_2$ or OH masers. We compiled two different samples. The first one comprises all known PNe with confirmed OH and/or H$_2$O maser emission, as well as two candidate PNe showing OH masers. For the second sample, we compiled single-dish SiO maser detections in the literature, and compared them with catalogs of PNe and radio continuum emission (which could trace photoionized gas in PNe). We identified five targets (either PN or radio continuum sources) within the beam of the single-dish SiO maser observations. We then carried out interferometric observations of both samples with the Australia Telescope Compact Array, to confirm the spatial association between continuum and SiO maser emission. We find no SiO maser emission associated with any confirmed or candidate PN. In all targets, except IRAS 17390$-$3014, there is no spatial coincidence between SiO masers and radio continuum emission. While in IRAS 17390$-$3014 we cannot completely rule out a possible association, it is unlikely that the radio continuum emission arises from a PN. The absence of SiO maser emission in PNe showing OH or H$_2$O masers is of special interest, since thermal SiO emission has been reported in at least one of these targets, indicating that SiO molecules can be present in the gas phase. Since some maser-emitting PNe show evidence of having O-rich outer envelopes, and carbon- (C-) rich central stars and inner envelopes, we speculate that SiO abundance could be very low in the central regions where physical conditions are optimal for maser pumping, and C-bearing molecules may be dominant in the gas phase at those locations.

Luminescent and magnetic Y2O3: Er3+-Yb3+@γ-Fe2O3 bifunctional broadband emitting nanocomposites

The development of novel nanocomposites containing upconverting luminescent materials and magnetic nanoparticles have shown their potential applications in the hyperthermia and bio-imaging. In this regards, the search for new class of nanocomposites, which is responsive to magnetic and optical guiding in medical fields are in demand. To resolve the problem, bifunctional upconverting Y2O3: Er3+-Yb3+@γ-Fe2O3 nanocomposites have been synthesized through ball milling approach. Nanocomposites are able to upconvert NIR photons into overall yellowish-white colour broadband visible emission in 400–900 nm wavelength range at room temperature under 980 nm CW laser diode excitation. Thermal conductivity study shows an improved phonon scattering process in the Y2O3: Er3+-Yb3+@γ-Fe2O3 (∼ 0.0681 W/mK) nanocomposites as compared to Y2O3: Er3+-Yb3+ (∼ 0.0750 W/mK) phosphors due to grain boundary expansion. Broadband UC emission is originated via Yb-Yb dimer formation and heat associated continuum emission is reported due to photon avalanche (∼ 6 NIR photons) phenomenon. Besides, it also exhibits the attraction ability towards the magnet. Therefore, the developed nanocomposites can be used in converting the NIR radiation into broadband upconversion emission and luminescence imaging applications.

Merging Signatures in an Offset Lyman Continuum Emitter at Redshift 3.8

Lyman continuum (LyC) emitters at z > 3 provide critical samples for studying the contribution of galaxies to the ionizing background in the epoch of reionization. We collect a sample of z > 3 LyC emitters, a dominant fraction (∼60%–70%) of which show spatial offsets between LyC emission and the nonionizing continuum. From this sample, especially, we find a case of an offset LyC emitter, CDFS-6664 (z = 3.797), which shows two components in the high-resolution Hubble Space Telescope and James Webb Space Telescope images. The exceptionally rich data set of CDFS-6664 enables us to extract the two components across multiple wavelengths and estimate their physical properties. We show that CDFS-6664 is consistent with a major merger system with boosted star formation in both components and that the offset LyC emission is most likely associated with the bluer and younger component in this merging system. Our result offers an example in which the offset can be caused by a merger. Future observations of more offset LyC emitters would elucidate the role that mergers play in the escape of LyC photons.

Multiwavelength high-resolution polarimetric imaging of second-generation disc around post-AGB binary IRAS 08544–4431 with SPHERE

ABSTRACT Exploring the formation and evolution of second-generation circumbinary discs around evolved binary stars, such as post-asymptotic giant branch (post-AGB) and post-red giant branch binaries, provides valuable insights into the complex binary interaction process that concludes the red-giant phase of evolution in these systems. Additionally, it offers a novel opportunity to investigate the formation of second-generation planets within dusty discs surrounding evolved stars. We present a pilot multiwavelength polarimetric imaging study of the post-AGB binary system IRAS 08544–4431 using the European Southern Observatory–Very Large Telescope/Spectro-Polarimetric High-contrast Exoplanet Research (VLT/SPHERE) instrument. This study is focused on optical V- and $I^{\prime }$-band Zurich Imaging Polarimeter (ZIMPOL) data to complement near-infrared (near-IR) H-band IRDIS data presented previously. The study aims to investigate the dust scattering properties and surface morphology of the post-AGB circumbinary disc as a function of wavelength. We successfully resolved the extended disc structure of IRAS 08544–4431, revealing a complex disc morphology, high polarimetric disc brightness (up to $\sim$1.5 %), and significant forward scattering at optical wavelengths. Additionally, we found that the disc shows a grey polarimetric colour in both optical and near-IR. The findings highlight similarities between post-AGB circumbinary discs and protoplanetary discs, suggesting submicron-sized porous aggregates as the dominant surface dust composition, and indicating potential warping within the disc. However, further expansion of the multiwavelength analysis to a larger sample of post-AGB binary systems, as well as high-resolution observations of dust continuum and gas emission, is necessary to fully explore the underlying structure of post-AGB circumbinary discs and associated physical mechanisms.

REBELS-25: discovery of a dynamically cold disc galaxy at z = 7.31

ABSTRACT We present high-resolution ($\sim 0.14$ arcsec = 710 pc) Atacama Large Millimetre/submillimetre Array [C ii] 158 $\mu$m and dust continuum follow-up observations of REBELS-25, a [C ii]-luminous ($L_{\mathrm{[CII]}}=(1.7\pm 0.2)\times 10^9\, \mathrm{L_{\odot }}$) galaxy at redshift $z=7.3065\pm 0.0001$. These high-resolution, high signal-to-noise observations allow us to study the sub-kpc morphology and kinematics of this massive ($M_* = 8^{+4}_{-2} \times 10^9 \mathrm{{\rm M}_{\odot }}$) star-forming (SFR$_{\mathrm{UV+IR}} = 199^{+101}_{-63} \mathrm{{\rm M}_{\odot }} \mathrm{yr}^{-1}$) galaxy in the Epoch of Reionization. By modelling the kinematics with $^{\mathrm{3D}}$BAROLO, we find it has a low-velocity dispersion ($\bar{\sigma } = 33^{+9}_{-7}$ km s$^{-1}$) and a high ratio of ordered-to-random motion ($V_{\mathrm{rot, ~max}}/\bar{\sigma } = 11 ^{+6}_{-5}$), indicating that REBELS-25 is a dynamically cold disc. Additionally, we find that the [C ii] distribution is well fit by a near-exponential disc model, with a Sérsic index, n, of $1.3 \pm 0.2$, and we see tentative evidence of more complex non-axisymmetric structures suggestive of a bar in the [C ii] and dust continuum emission. By comparing to other high spatial resolution cold gas kinematic studies, we find that dynamically cold discs seem to be more common in the high-redshift Universe than expected based on prevailing galaxy formation theories, which typically predict more turbulent and dispersion-dominated galaxies in the early Universe as an outcome of merger activity, gas accretion, and more intense feedback. This higher degree of rotational support seems instead to be consistent with recent cosmological simulations that have highlighted the contrast between cold and warm ionized gas tracers, particularly for massive galaxies. We therefore show that dynamically settled disc galaxies can form as early as 700 Myr after the big bang

Flare heating of the chromosphere: Observations of flare continuum from GREGOR and IRIS

Context. On 2022 May 4, an M5.7 flare erupted in the active region NOAA 13004, which was the target of a coordinated campaign between GREGOR, IRIS, Hinode, and ground-based instruments at the Ondřejov observatory. A flare kernel located at the edge of a pore was co-observed by the IRIS slit and GREGOR HiFI+ imagers. Aims. We investigated the flare continuum enhancement at different wavelength ranges in order to derive the temperature of the chromospheric layer heated during the flare. Methods. All datasets were aligned to IRIS slit-jaw images. We selected a pixel along the IRIS slit where the flare kernel was captured and evaluated multi-wavelength light curves within it. We defined a narrow IRIS near-UV band that comprises only continuum emission. The method, which assumes that the flare continuum enhancement is due to optically thin emission from hydrogen recombination processes, was applied to obtain a lower limit on the temperature in the layer where the continuum enhancement was formed. Results. We determined a lower limit for the temperature and its time evolution in the chromospheric layer heated during the flare in the range of (3–15) ×103 K. The mean electron density in that layer was estimated to be ∼1 × 1013 cm−3. Conlcusions. Multi-wavelength flare co-observations are a rich source of diagnostics. Due to the rapidly evolving nature of flares, the sit-and-stare mode is key to achieving a high temporal cadence that allows one to thoroughly analyse the same flare structure.

Early Planet Formation in Embedded Disks. XI. A High-resolution View Toward the BHR 71 Class 0 Protostellar Wide Binary

We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of the binary Class 0 protostellar system BHR 71 IRS1 and IRS2 as part of the Early Planet Formation in Embedded Disks (eDisk) ALMA Large Program. We describe the 12CO (J = 2–1), 13CO (J = 2–1), C18O (J = 2–1), H2CO (J = 32,1–22,0), and SiO (J = 5–4) molecular lines along with the 1.3 mm continuum at high spatial resolution (∼0.″08 or ∼5 au). Dust continuum emission is detected toward BHR 71 IRS1 and IRS2, with a central compact component and extended continuum emission. The compact components are smooth and show no sign of substructures such as spirals, rings, or gaps. However, there is a brightness asymmetry along the minor axis of the presumed disk in IRS1, possibly indicative of an inclined geometrically and optically thick disk-like component. Using a position–velocity diagram analysis of the C18O line, clear Keplerian motions were not detected toward either source. If Keplerian rotationally supported disks are present, they are likely deeply embedded in their envelope. However, we can set upper limits of the central protostellar mass of 0.46 M ⊙ and 0.26 M ⊙ for BHR 71 IRS1 and BHR 71 IRS2, respectively. Outflows traced by 12CO and SiO are detected in both sources. The outflows can be divided into two components, a wide-angle outflow and a jet. In IRS1, the jet exhibits a double helical structure, reflecting the removal of angular momentum from the system. In IRS2, the jet is very collimated and shows a chain of knots, suggesting episodic accretion events.

Magnetic Fields in Massive Star-forming Regions (MagMaR). IV. Tracing the Magnetic Fields in the O-type Protostellar System IRAS 16547–4247

The formation of the massive stars, and in particular, the role that the magnetic fields play in their early evolutionary phase is still far from being completely understood. Here, we present the Atacama Large Millimeter/submillimeter Array 1.2 mm full polarized continuum and H13CO+(3−2), CS(5−4), and HN13C(3−2) line observations with a high angular resolution (∼0.″4 or 1100 au). In the 1.2 mm continuum emission, we reveal a dusty envelope surrounding the massive protostars, IRAS16547-E and IRAS16547-W, with dimensions of ∼10,000 au. This envelope has a biconical structure likely carved by the powerful thermal radio jet present in region. The magnetic field vectors follow very well the biconical envelope. The polarization fraction is ∼2.0% in this region. Some of these vectors seem to converge to IRAS 16547-E and IRAS 16547-W, the most massive protostars. Moreover, the velocity fields revealed from the spectral lines H13CO+(3−2) and HN13C(3−2) show velocity gradients with a good correspondence with the magnetic fields, which maybe are tracing the cavities of molecular outflows or maybe infalling in some parts. We derived a magnetic field strength in some filamentary regions that goes from 2 to 6.1 mG. We also find that the CS(5−4) molecular line emission reveals multiple outflow cavities or bow shocks with different orientations, some of which seem to follow the NW–SE radio thermal jet.

The Clearing Timescale for Infrared-selected Star Clusters in M83 with HST

We present an analysis of Hubble Space Telescope data from Wide Field Camera 3 (WFC3)/Ultraviolet Imaging Spectrometer, WFC3/IR, and the Advanced Camera for Surveys, investigating the young stellar cluster (YSC) population in the face-on spiral galaxy M83. Within the field of view of the IR pointings, we identify 454 sources with compact F814W continuum and Paβ line emission with a S/N ≥ 3 as possible YSC candidates embedded in dust. We refine this selection to 97 candidates based on their spectral energy distributions, multiwavelength morphology, and photometric uncertainties. For sources that are detected in all bands and have mass >102.8 M ⊙ (53 sources), we find that by 2 Myr 75% of IR-selected star clusters have an A V ≤ 1 and that by 3 Myr the fraction rises to ∼82%. This evidence of early clearing implies that presupernova (pre-SN) feedback from massive stars is responsible for clearing the majority of the natal gas and dust that surround IR-selected star clusters in M83. Further, this result is consistent with previous estimates based on WFC3 observations and adds to the growing body of literature suggesting pre-SN feedback to be crucial for YSC emergence in normal star-forming galaxies. Finally, we find a weak correlation between the YSC concentration index and age over the first 10 Myr, which matches previous studies and indicates little or no change in the size of YSCs in M83 during their early evolution.

A Nonparametric Morphological Analysis of Hα Emission in Bright Dwarfs Using the Merian Survey

Using medium-band imaging from the newly released Merian Survey, we conduct a nonparametric morphological analysis of Hα emission maps and stellar continua for a sample of galaxies with 8≲log(M⋆/M⊙)<10.3 at 0.064 < z < 0.1. We present a novel method for estimating the stellar continuum emission through the Merian Survey’s N708 medium-band filter, which we use to measure Hα emission and produce Hα maps for our sample of galaxies with seven-band Merian photometry and available spectroscopy. We measure nonparametric morphological statistics for the Hα and stellar continuum images, explore how the morphology of the Hα differs from the continuum, and investigate how the parameters evolve with the galaxies’ physical properties. In agreement with previous results for more massive galaxies, we find that the asymmetry of the stellar continuum increases with specific star formation rate (sSFR), and we extend the trend to lower masses, also showing that it holds for the asymmetry of the Hα emission. We find that the lowest-mass galaxies with the highest sSFR have Hα emission that is consistently heterogeneous and compact, while the less active galaxies in this mass range have Hα emission that appears diffuse. At higher masses, our data do not span a sufficient range in sSFR to evaluate whether similar trends apply. We conclude that high sSFRs in low-mass galaxies likely result from dynamical instabilities that compress a galaxy’s molecular gas to a dense region near the center.

ALMA Detection of Masers and Dasars in the Hydrogen Recombination Lines of the Planetary Nebula Mz3

The hydrogen recombination lines H30α, H40α, H42α, H50β, and H57γ and the underlying bremsstrahlung continuum emission were detected with ALMA in the bipolar nebula Mz3. The source was not spatially resolved, but the velocity profile of the H30α line shows clear indication of maser amplification, confirming previous reports of laser amplification in the far-infrared H recombination lines observed with Herschel Space Observatory. Comparison between the flux densities of the H50β, H40α, and H42α lines show overcooling, or darkness amplification by stimulated absorption (dasar effect) at the LSR velocity of about −25 km s−1, which constrains the density of the absorbing region to about 103 cm−3. The H30α line, on the other hand, presents maser lines at LSR velocities of −69 and −98 km s−1, which indicates ionized gas with densities close to 107 cm−3. Although the source of emission was not resolved, it was possible to find the central position of the images for each velocity interval, which resulted in a well defined position–velocity distribution.