arXiv subjects

Charles J. Law

Publications and source records attributed to Charles J. Law.

At least 55 records · Page 3Linked to original sources

arXiv2023

C I Traces the Disk Atmosphere in the IM Lup Protoplanetary Disk

The central star and its energetic radiation fields play a vital role in setting the vertical and radial chemical structure of planet-forming disks. We present observations that, for the first time, clearly reveal the UV-irradiated surface of a protoplanetary disk. Specifically, we spatially resolve the atomic-to-molecular (C I-to-CO) transition in the IM Lup disk with ALMA archival observations of [C I] $^3$P$_1$-$^3$P$_0$. We derive a C I emitting height of z/r $\gtrsim$ 0.5 with emission detected out to a radius of ${\approx}$600 au. Compared to other systems with C I heights inferred from unresolved observations or models, the C I layer in the IM Lup disk is at scale heights almost double that of other disks, confirming its highly flared nature. C I arises from a narrow, optically-thin layer that is substantially more elevated than that of $^{12}$CO (z/r $\approx$ 0.3-0.4), which allows us to directly constrain the physical gas conditions across the C I-to-CO transition zone. We also compute a radially-resolved C I column density profile and find a disk-averaged C I column density of 2$\times10^{16}$ cm$^{-2}$, which is ${\approx}$3-20$\times$ lower than that of other disks with spatially-resolved C I detections. We do not find evidence for vertical substructures or spatially-localized deviations in C I due, e.g., to either an embedded giant planet or a photoevaporative wind that have been proposed in the IM Lup disk, but emphasize that deeper observations are required for robust constraints.

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arXiv2023

MAPS: Constraining Serendipitous Time Variability in Protoplanetary Disk Molecular Ion Emission

Theoretical models and observations suggest that the abundances of molecular ions in protoplanetary disks should be highly sensitive to the variable ionization conditions set by the young central star. We present a search for temporal flux variability of HCO+ J=1-0, which was observed as a part of the Molecules with ALMA at Planet-forming Scales (MAPS) ALMA Large Program. We split out and imaged the line and continuum data for each individual day the five sources were observed (HD 163296, AS 209, GM Aur, MWC 480, and IM Lup, with between 3 to 6 unique visits per source). Significant enhancement (>3σ) was not observed, but we find variations in the spectral profiles in all five disks. Variations in AS 209, GM Aur, and HD 163296 are tentatively attributed to variations in HCO+ flux, while variations in IM Lup and MWC 480 are most likely introduced by differences in the \textit{uv} coverage, which impact the amount of recovered flux during imaging. The tentative detections and low degree of variability are consistent with expectations of X-ray flare driven HCO+ variability, which requires relatively large flares to enhance the HCO+ rotational emission at significant (>20%) levels. These findings also demonstrate the need for dedicated monitoring campaigns with high signal to noise ratios to fully characterize X-ray flare driven chemistry.

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arXiv2023

Tracing snowlines and C/O ratio in a planet-hosting disk: ALMA molecular line observations towards the HD169142 disk

The composition of a forming planet is set by the material it accretes from its parent protoplanetary disk. Therefore, it is crucial to map the chemical make-up of the gas in disks to understand the chemical environment of planet formation. This paper presents molecular line observations taken with the Atacama Large Millimeter/submillimeter Array of the planet-hosting disk around the young star HD 169142. We detect N2H+, CH3OH, [CI], DCN, CS, C34S, 13CS, H2CS, H2CO, HC3N and c-C3H2 in this system for the first time. Combining these data with the recent detection of SO and previously published DCO+ data, we estimate the location of H2O and CO snowlines and investigate radial variations in the gas phase C/O ratio. We find that the HD 169142 disk has a relatively low N2H+ flux compared to the disks around Herbig stars HD 163296 and MWC 480 indicating less CO freeze-out and place the CO snowline beyond the millimetre disk at ~150 au. The detection of CH3OH from the inner disk is consistent with the H2O snowline being located at the edge of the central dust cavity at ~20 au. The radially varying CS/SO ratio across the proposed H2O snowline location is consistent with this interpretation. Additionally, the detection of CH3OH in such a warm disk adds to the growing evidence supporting the inheritance of complex ices in disks from the earlier, colder stages of star formation. Finally, we propose that the giant HD 169142 b located at 37 au is forming between the CO2 and H2O snowlines where the local elemental make of the gas is expected to have C/O=1.0.

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arXiv2023

SO and SiS Emission Tracing an Embedded Planet and Compact $^{12}$CO and $^{13}$CO Counterparts in the HD 169142 Disk

Planets form in dusty, gas-rich disks around young stars, while at the same time, the planet formation process alters the physical and chemical structure of the disk itself. Embedded planets will locally heat the disk and sublimate volatile-rich ices, or in extreme cases, result in shocks that sputter heavy atoms such as Si from dust grains. This should cause chemical asymmetries detectable in molecular gas observations. Using high-angular-resolution ALMA archival data of the HD 169142 disk, we identify compact SO J=8$_8$-7$_7$ and SiS J=19-18 emission coincident with the position of a ${\sim}$2 M$_{\rm{Jup}}$ planet seen as a localized, Keplerian NIR feature within a gas-depleted, annular dust gap at ${\approx}$38 au. The SiS emission is located along an azimuthal arc and has a similar morphology as a known $^{12}$CO kinematic excess. This is the first tentative detection of SiS emission in a protoplanetary disk and suggests that the planet is driving sufficiently strong shocks to produce gas-phase SiS. We also report the discovery of compact $^{12}$CO and $^{13}$CO J=3-2 emission coincident with the planet location. Taken together, a planet-driven outflow provides the best explanation for the properties of the observed chemical asymmetries. We also resolve a bright, azimuthally-asymmetric SO ring at ${\approx}$24 au. While most of this SO emission originates from ice sublimation, its asymmetric distribution implies azimuthal temperature variations driven by a misaligned inner disk or planet-disk interactions. Overall, the HD 169142 disk shows several distinct chemical signatures related to giant planet formation and presents a powerful template for future searches of planet-related chemical asymmetries in protoplanetary disks.

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arXiv2023

Molecules with ALMA at Planet-forming Scales (MAPS). Complex Kinematics in the AS 209 Disk Induced by a Forming Planet and Disk Winds

We study the kinematics of the AS 209 disk using the J=2-1 transitions of $^{12}$CO, $^{13}$CO, and C$^{18}$O. We derive the radial, azimuthal, and vertical velocity of the gas, taking into account the lowered emission surface near the annular gap at ~1.7 (200 au) within which a candidate circumplanetary disk-hosting planet has been reported previously. In $^{12}$CO and $^{13}$CO, we find a coherent upward flow arising from the gap. The upward gas flow is as fast as $150~{\rm m~s}^{-1}$ in the regions traced by $^{12}$CO emission, which corresponds to about 50% of the local sound speed or $6\%$ of the local Keplerian speed. Such an upward gas flow is difficult to reconcile with an embedded planet alone. Instead, we propose that magnetically driven winds via ambipolar diffusion are triggered by the low gas density within the planet-carved gap, dominating the kinematics of the gap region. We estimate the ambipolar Elsasser number, Am, using the HCO$^+$ column density as a proxy for ion density and find that Am is ~0.1 at the radial location of the upward flow. This value is broadly consistent with the value at which numerical simulations find ambipolar diffusion drives strong winds. We hypothesize the activation of magnetically-driven winds in a planet-carved gap can control the growth of the embedded planet. We provide a scaling relationship which describes the wind-regulated terminal mass: adopting parameters relevant to 100 au from a solar-mass star, we find the wind-regulated terminal mass is about one Jupiter mass, which may help explain the dearth of directly imaged super-Jovian-mass planets.

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arXiv2023

An SMA Survey of Chemistry in Disks around Herbig AeBe Stars

Protoplanetary disks around Herbig AeBe stars are exciting targets for studying the chemical environments where giant planets form. Save for a few disks, however, much of Herbig AeBe disk chemistry is an open frontier. We present a Submillimeter Array (SMA) $\sim$213-268 GHz pilot survey of mm continuum, CO isotopologues, and other small molecules in disks around five Herbig AeBe stars (HD 34282, HD 36112, HD 38120, HD 142666, and HD 144432). We detect or tentatively detect $^{12}$CO 2--1 and $^{13}$CO 2--1 from four disks; C$^{18}$O 2--1 and HCO$^+$ 3--2 from three disks; HCN 3--2, CS 5--4, and DCO$^+$ 3--2 from two disks; and C$_2$H 3--2 and DCN 3--2 from one disk each. H$_2$CO 3--2 is undetected at the sensitivity of our observations. The mm continuum images of HD 34282 suggest a faint, unresolved source $\sim$5\farcs0 away, which could arise from a distant orbital companion or an extended spiral arm. We fold our sample into a compilation of T Tauri and Herbig AeBe/F disks from the literature. Altogether, most line fluxes generally increase with mm continuum flux. Line flux ratios between CO 2--1 isotopologues are nearest to unity for the Herbig AeBe/F disks. This may indicate emitting layers with relatively similar, warmer temperatures and more abundant CO relative to disk dust mass. Lower HCO$^+$ 3--2 flux ratios may reflect less ionization in Herbig AeBe/F disks. Smaller detection rates and flux ratios for DCO$^+$ 3--2, DCN 3--2, and H$_2$CO 3--2 suggest smaller regimes of cold chemistry around the luminous Herbig AeBe/F stars.

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arXiv2023

Cold Deuterium Fractionation in the Nearest Planet-Forming Disk

Deuterium fractionation provides a window to the thermal history of volatiles in the solar system and protoplanetary disks. While evidence of active molecular deuteration has been observed towards a handful of disks, it remains unclear whether this chemistry affects the composition of forming planetesimals due to limited observational constraints on the radial and vertical distribution of deuterated molecules. To shed light on this question, we introduce new ALMA observations of DCO$^+$ and DCN $J=2-1$ at an angular resolution of $0.5"$ (30 au) and combine them with archival data of higher energy transitions towards the protoplanetary disk around TW Hya. We carry out a radial excitation analysis assuming both LTE and non-LTE to localize the physical conditions traced by DCO$^+$ and DCN emission in the disk, thus assessing deuterium fractionation efficiencies and pathways at different disk locations. We find similar disk-averaged column densities of $1.9\times10^{12}$ and $9.8\times10^{11}$ cm$^{-2}$ for DCO$^{+}$ and DCN, with typical kinetic temperatures for both molecules of 20-30K, indicating a common origin near the comet- and planet-forming midplane. The observed DCO$^+$/DCN abundance ratio, combined with recent modeling results, provide tentative evidence of a gas phase C/O enhancement within $<40$ au. Observations of DCO$^+$ and DCN in other disks, as well as HCN and HCO$^+$, will be necessary to place the trends exhibited by TW Hya in context, and fully constrain the main deuteration mechanisms in disks.

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arXiv2023

HST Proper Motion Measurements of Supernova Remnant N132D: Center of Expansion and Age

We present proper motion measurements of oxygen-rich ejecta of the LMC supernova remnant N132D using two epochs of Hubble Space Telescope Advanced Camera for Surveys data spanning 16 years. The proper motions of 120 individual knots of oxygen-rich gas were measured and used to calculate a center of expansion (CoE) of $α$=05:25:01.71 and $δ$=-69:38:41.64 (J2000) with a 1-$σ$ uncertainty of 2.90 arcseconds. This new CoE measurement is 9.2 and 10.8 arcseconds from two previous CoE estimates based on the geometry of the optically emitting ejecta. We also derive an explosion age of 2770 $\pm$ 500 yr, which is consistent with recent age estimates of $\approx 2500$ yr made from 3D ejecta reconstructions. We verify our estimates of the CoE and age using a new automated procedure that detected and tracked the proper motions of 137 knots, with 73 knots that overlap with the visually identified knots. We find the proper motions of ejecta are still ballistic, despite the remnant's age, and are consistent with the notion that the ejecta are expanding into an ISM cavity. Evidence for explosion asymmetry from the parent supernova is also observed. Using the visually measured proper motion measurements and corresponding center of expansion and age, we compare N132D to other supernova remnants with proper motion ejecta studies.

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arXiv2022

Mapping Protoplanetary Disk Vertical Structure with CO Isotopologue Line Emission

High spatial resolution observations of CO isotopologue line emission in protoplanetary disks at mid-inclinations (${\approx}$30-75°) allow us to characterize the gas structure in detail, including radial and vertical substructures, emission surface heights and their dependencies on source characteristics, and disk temperature profiles. By combining observations of a suite of CO isotopologues, we can map the 2D (r, z) disk structure from the disk upper atmosphere, as traced by CO, to near the midplane, as probed by less abundant isotopologues. Here, we present high angular resolution (${\lesssim}$0."1 to ${\approx}$0."2; ${\approx}$15-30 au) observations of CO, $^{13}$CO, and C$^{18}$O in either or both J=2-1 and J=3-2 lines in the transition disks around DM Tau, Sz 91, LkCa 15, and HD 34282. We derived line emission surfaces in CO for all disks and in $^{13}$CO for the DM Tau and LkCa 15 disks. With these observations, we do not resolve the vertical structure of C$^{18}$O in any disk, which is instead consistent with C$^{18}$O emission originating from the midplane. Both the J=2-1 and J=3-2 lines show similar heights. Using the derived emission surfaces, we computed radial and vertical gas temperature distributions for each disk, including empirical temperature models for the DM Tau and LkCa 15 disks. After combining our sample with literature sources, we find that $^{13}$CO line emitting heights are also tentatively linked with source characteristics, e.g., stellar host mass, gas temperature, disk size, and show steeper trends than seen in CO emission surfaces.

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arXiv2022

UV-driven Chemistry as a Signpost for Late-stage Planet Formation

The chemical reservoir within protoplanetary disks has a direct impact on planetary compositions and the potential for life. A long-lived carbon-and nitrogen-rich chemistry at cold temperatures (<=50K) is observed within cold and evolved planet-forming disks. This is evidenced by bright emission from small organic radicals in 1-10 Myr aged systems that would otherwise have frozen out onto grains within 1 Myr. We explain how the chemistry of a planet-forming disk evolves from a cosmic-ray/X-ray-dominated regime to an ultraviolet-dominated chemical equilibrium. This, in turn, will bring about a temporal transition in the chemical reservoir from which planets will accrete. This photochemical dominated gas phase chemistry develops as dust evolves via growth, settling and drift, and the small grain population is depleted from the disk atmosphere. A higher gas-to-dust mass ratio allows for deeper penetration of ultraviolet photons is coupled with a carbon-rich gas (C/O > 1) to form carbon-bearing radicals and ions. This further results in gas phase formation of organic molecules, which then would be accreted by any actively forming planets present in the evolved disk.

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arXiv2022

Clustered Formation of Massive Stars within an Ionized Rotating Disk

We present ALMA observations with a 800 au resolution and radiative-transfer modelling of the inner part ($r\approx6000$ au) of the ionized accretion flow around a compact star cluster in formation at the center of the luminous ultra-compact (UC) HII region G10.6-0.4. We modeled the flow with an ionized Keplerian disk with and without radial motions in its outer part, or with an external Ulrich envelope. The MCMC fits to the data give total stellar masses $M_\star$ from 120 to $200~M_\odot$, with much smaller ionized-gas masses $M_\mathrm{ion-gas} = 0.2$ to $0.25~M_\odot$. The stellar mass is distributed within the gravitational radius $R_g\approx 1000$ to 1500 au, where the ionized gas is bound. The viewing inclination angle from the face-on orientation is $i = 49$ to $56~°$. Radial motions at radii $r > R_g$ converge to $v_{r,0} \approx 8.7$ km/s, or about the speed of sound of ionized gas, indicating that this gas is marginally unbound at most. From additional constraints on the ionizing-photon rate and far-IR luminosity of the region, we conclude that the stellar cluster consists of a few massive stars with $M_\mathrm{star} = 32$ to $60~M_\odot$, or one star in this range of masses accompanied by a population of lower-mass stars. Any active accretion of ionized gas onto the massive (proto)stars is residual. The inferred cluster density is very large, comparable to that reported at similar scales in the Galactic Center. Stellar interactions are likely to occur within the next Myr.

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arXiv2022

Molecules with ALMA at Planet-forming Scales (MAPS). A Circumplanetary Disk Candidate in Molecular Line Emission in the AS 209 Disk

We report the discovery of a circumplanetary disk (CPD) candidate embedded in the circumstellar disk of the T Tauri star AS 209 at a radial distance of about 200 au (on-sky separation of 1."4 from the star at a position angle of $161^\circ$), isolated via $^{13}$CO $J=2-1$ emission. This is the first instance of CPD detection via gaseous emission capable of tracing the overall CPD mass. The CPD is spatially unresolved with a $117\times82$ mas beam and manifests as a point source in $^{13}$CO, indicating that its diameter is $\lesssim14$ au. The CPD is embedded within an annular gap in the circumstellar disk previously identified using $^{12}$CO and near-infrared scattered light observations, and is associated with localized velocity perturbations in $^{12}$CO. The coincidence of these features suggests that they have a common origin: an embedded giant planet. We use the $^{13}$CO intensity to constrain the CPD gas temperature and mass. We find that the CPD temperature is $\gtrsim35$ K, higher than the circumstellar disk temperature at the radial location of the CPD, 22 K, suggesting that heating sources localized to the CPD must be present. The CPD gas mass is $\gtrsim 0.095 M_{\rm Jup} \simeq 30 M_{\rm Earth}$ adopting a standard $^{13}$CO abundance. From the non-detection of millimeter continuum emission at the location of the CPD ($3σ$ flux density $\lesssim26.4~μ$Jy), we infer that the CPD dust mass is $\lesssim 0.027 M_{\rm Earth} \simeq 2.2$ lunar masses, indicating a low dust-to-gas mass ratio of $\lesssim9\times10^{-4}$. We discuss the formation mechanism of the CPD-hosting giant planet on a wide orbit in the framework of gravitational instability and pebble accretion.

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arXiv2022

Molecules with ALMA at Planet-forming Scales (MAPS) III: Characteristics of Radial Chemical Substructures

The Molecules with ALMA at Planet-forming Scales (MAPS) Large Program provides a detailed, high resolution (${\sim}$10-20 au) view of molecular line emission in five protoplanetary disks at spatial scales relevant for planet formation. Here, we present a systematic analysis of chemical substructures in 18 molecular lines toward the MAPS sources: IM Lup, GM Aur, AS 209, HD 163296, and MWC 480. We identify more than 200 chemical substructures, which are found at nearly all radii where line emission is detected. A wide diversity of radial morphologies - including rings, gaps, and plateaus - is observed both within each disk and across the MAPS sample. This diversity in line emission profiles is also present in the innermost 50 au. Overall, this suggests that planets form in varied chemical environments both across disks and at different radii within the same disk. Interior to 150 au, the majority of chemical substructures across the MAPS disks are spatially coincident with substructures in the millimeter continuum, indicative of physical and chemical links between the disk midplane and warm, elevated molecular emission layers. Some chemical substructures in the inner disk and most chemical substructures exterior to 150 au cannot be directly linked to dust substructure, however, which indicates that there are also other causes of chemical substructures, such as snowlines, gradients in UV photon fluxes, ionization, and radially-varying elemental ratios. This implies that chemical substructures could be developed into powerful probes of different disk characteristics, in addition to influencing the environments within which planets assemble. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.

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arXiv2022

CO Line Emission Surfaces and Vertical Structure in Mid-Inclination Protoplanetary Disks

High spatial resolution CO observations of mid-inclination (30-75°) protoplanetary disks offer an opportunity to study the vertical distribution of CO emission and temperature. The asymmetry of line emission relative to the disk major axis allows for a direct mapping of the emission height above the midplane, and for optically-thick, spatially-resolved emission in LTE, the intensity is a measure of the local gas temperature. Our analysis of ALMA archival data yields CO emission surfaces, dynamically-constrained stellar host masses, and disk atmosphere gas temperatures for the disks around: HD 142666, MY Lup, V4046 Sgr, HD 100546, GW Lup, WaOph 6, DoAr 25, Sz 91, CI Tau, and DM Tau. These sources span a wide range in stellar masses (0.50-2.10 M$_{\odot}$), ages (${\sim}$0.3-23 Myr), and CO gas radial emission extents (${\approx}$200-1000 au). This sample nearly triples the number of disks with mapped emission surfaces and confirms the wide diversity in line emitting heights ($z/r\approx0.1$ to ${\gtrsim}0.5$) hinted at in previous studies. We compute radial and vertical CO gas temperature distributions for each disk. A few disks show local temperature dips or enhancements, some of which correspond to dust substructures or the proposed locations of embedded planets. Several emission surfaces also show vertical substructures, which all align with rings and gaps in the millimeter dust. Combining our sample with literature sources, we find that CO line emitting heights weakly decline with stellar mass and gas temperature, which, despite large scatter, is consistent with simple scaling relations. We also observe a correlation between CO emission height and disk size, which is due to the flared structure of disks. Overall, CO emission surfaces trace ${\approx}2$-$5\times$ gas pressure scale heights (H$_{\rm{g}}$) and could potentially be calibrated as empirical tracers of H$_{\rm{g}}$.

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arXiv2022

Protostellar and Protoplanetary Disk Masses in the Serpens Region

We present the results from an Atacama Large Millimeter/Submillimeter Array (ALMA) 1.3 mm continuum and $^{12}$CO ($J=2-1$) line survey spread over 10 square degrees in the Serpens star-forming region of 320 young stellar objects, 302 of which are likely members of Serpens (16 Class I, 35 Flat spectrum, 235 Class II, and 16 Class III). From the continuum data, we derive disk dust masses and show that they systematically decline from Class I to Flat spectrum to Class II sources. Grouped by stellar evolutionary state, the disk mass distributions are similar to other young ($<3$ Myr) regions, indicating that the large scale environment of a star-forming region does not strongly affect its overall disk dust mass properties. These comparisons between populations reinforce previous conclusions that disks in the Ophiuchus star-forming region have anomalously low masses at all evolutionary stages. Additionally, we find a single deeply embedded protostar that has not been documented elsewhere in the literature and, from the CO line data, 15 protostellar outflows which we catalog here.

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arXiv2021

Molecules with ALMA at Planet-forming Scales (MAPS). X. Studying deuteration at high angular resolution toward protoplanetary disks

Deuterium fractionation is dependent on various physical and chemical parameters. Thus, the formation location and thermal history of material in the solar system is often studied by measuring its D/H ratio. This requires knowledge about the deuteration processes operating during the planet formation era. We aim to study these processes by radially resolving the DCN/HCN (at 0.3" resolution) and N$_2$D$^+$/N$_2$H$^+$ (0.3 to 0.9") column density ratios toward the five protoplanetary disks observed by the Molecules with ALMA at Planet-forming scales (MAPS) Large Program. DCN is detected in all five sources, with one newly reported detection. N$_2$D$^+$ is detected in four sources, two of which are newly reported detections. We derive column density profiles that allow us to study the spatial variation of the DCN/HCN and N$_2$D$^+$/N$_2$H$^+$ ratios at high resolution. DCN/HCN varies considerably for different parts of the disks, ranging from $10^{-3}$ to $10^{-1}$. In particular, the inner disk regions generally show significantly lower HCN deuteration compared with the outer disk. In addition, our analysis confirms that two deuterium fractionation channels are active, which can alter the D/H ratio within the pool of organic molecules. N$_2$D$^+$ is found in the cold outer regions beyond $\sim$50 au, with N$_2$D$^+$/N$_2$H$^+$ ranging between $10^{-2}$ and 1 across the disk sample. This is consistent with the theoretical expectation that N$_2$H$^+$ deuteration proceeds via the low-temperature channel only. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.

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arXiv2021

First extragalactic measurement of the turbulence driving parameter: ALMA observations of the star-forming region N159E in the Large Magellanic Cloud

Studying the driving modes of turbulence is important for characterizing the impact of turbulence in various astrophysical environments. The driving mode of turbulence is parameterized by $b$, which relates the width of the gas density PDF to the turbulent Mach number; $b\approx 1/3$, $1$, and $0.4$ correspond to driving that is solenoidal, compressive, and a natural mixture of the two, respectively. In this work, we use high-resolution (sub-pc) ALMA $^{12}$CO ($J$ = $2-1$), $^{13}$CO ($J$ = $2-1$), and C$^{18}$O ($J$ = $2-1$) observations of filamentary molecular clouds in the star-forming region N159E (the Papillon Nebula) in the Large Magellanic Cloud (LMC) to provide the first measurement of turbulence driving parameter in an extragalactic region. We use a non-local thermodynamic equilibrium (NLTE) analysis of the CO isotopologues to construct a gas density PDF, which we find to be largely log-normal in shape with some intermittent features indicating deviations from lognormality. We find that the width of the log-normal part of the density PDF is comparable to the supersonic turbulent Mach number, resulting in $b \approx 0.9$. This implies that the driving mode of turbulence in N159E is primarily compressive. We speculate that the compressive turbulence could have been powered by gravo-turbulent fragmentation of the molecular gas, or due to compression powered by H I flows that led to the development of the molecular filaments observed by ALMA in the region. Our analysis can be easily applied to study the nature of turbulence driving in resolved star-forming regions in the local as well as the high-redshift Universe.

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arXiv2021

Hot corino chemistry in the Class I binary source Ser-emb 11

We report the detection of more than 120 emission lines corresponding to 8 complex organic molecules (CH3OH, CH3CH2OH, CH3OCH3, CH3OCHO, CH3COCH3, NH2CHO, CH2DCN, and CH3CH2CN) and 3 isotopologues (CH2DOH, 13CH3CN, and CH3C15N) toward the western component of the Ser-emb 11 binary young stellar object (YSO) using observations with the Atacama Large Millimeter/submillimeter Array at ~1 mm. The complex organic emission was unresolved with a ~0.5" beam (~220 au) in a compact region around the central protostar, and a population diagram analysis revealed excitation temperatures above 100 K for all COMs, indicating the presence of a hot corino. The estimated column densities were in the range of 10^17 - 10^18 cm^-2 for the O-bearing COMs, and three orders of magnitude lower for the N-bearing species. We also report the detection of H2CO and CH3OH emission in a nearby millimeter source that had not been previously catalogued. Ser-emb 11 is classified in the literature as a Class I source near the Class 0/I cutoff. The estimated COM relative abundances in Ser-emb 11 W and the other three Class I hot corino sources reported in the literature are consistent with those of Class 0 hot corinos, suggesting a continuity in the chemical composition of hot corinos during protostellar evolution.

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