Abstract
We present proper motion measurements of the 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
= 5
h
25
m
01.ˢ71 and
δ
= −69°38′41.″64 (J2000) with a 1
σ
uncertainty of 2.″90. This new CoE measurement is 9.″2 and 10.″8 from two previous CoE estimates based on the geometry of the optically emitting ejecta. We also derive an explosion age of 2770 ± 500 yr, which is consistent with recent age estimates of ≈2500 yr made from 3D ejecta reconstructions. We verified 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 that the proper motions of the ejecta are still ballistic, despite the remnant’s age, and are consistent with the notion that the ejecta are expanding into an interstellar medium cavity. Evidence for explosion asymmetry from the parent supernova is also observed. Using the visually measured proper motion measurements and corresponding CoE and age, we compare N132D to other supernova remnants with proper motion ejecta studies.
Abstract PDS 70 hosts two massive, still-accreting planets and the inclined orientation of its protoplanetary disk presents a unique opportunity to directly probe the vertical gas structure of a ...planet-hosting disk. Here, we use high-spatial-resolution (≈0.″1; 10 au) observations in a set of CO isotopologue lines and HCO + J = 4−3 to map the full 2D ( r , z ) disk structure from the disk atmosphere, as traced by 12 CO, to closer to the midplane, as probed by less abundant isotopologues and HCO + . In the PDS 70 disk, 12 CO traces a height of z / r ≈ 0.3, 13 CO is found at z / r ≈ 0.1, and C 18 O originates at, or near, the midplane. The HCO + surface arises from z / r ≈ 0.2 and is one of the few non-CO emission surfaces constrained with high-fidelity in disks to date. In the 12 CO J = 3−2 line, we resolve a vertical dip and steep rise in height at the cavity wall, making PDS 70 the first transition disk where this effect is directly seen in line-emitting heights. In the outer disk, the CO emission heights of PDS 70 appear typical for its stellar mass and disk size and are not substantially altered by the two inner embedded planets. By combining CO isotopologue and HCO + lines, we derive the 2D gas temperature structure and estimate a midplane CO snowline of ≈ 56–85 au. This implies that both PDS 70b and 70c are located interior to the CO snowline and are likely accreting gas with a high C/O ratio of ≈ 1.0, which provides context for future planetary atmospheric measurements from, e.g., JWST, and for properly modeling their formation histories.
Abstract
High spatial resolution CO observations of midinclination (≈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 Atacama Large Millimeter/submillimeter Array archival data yields CO emission surfaces, dynamically constrained stellar host masses, and disk atmosphere gas temperatures for the disks around the following: 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
⊙
), ages (∼0.3–23 Myr), and CO gas radial emission extents (≈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
≈ 0.1 to ≳0.5) hinted at in previous studies. We compute the 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 ≈2–5× gas pressure scale heights (H
g
) and could potentially be calibrated as empirical tracers of H
g
.
Abstract
Carbon chain molecules may be an important reservoir of reactive organics during star and planet formation. Carbon chains have been observed toward several low-mass young stellar objects ...(YSOs), but their typical abundances and chemical relationships in such sources are largely unconstrained. We present a carbon chain survey toward 16 deeply embedded (Class 0/I) low-mass protostars made with the IRAM 30 m telescope. Carbon chains are found to be common at this stage of protostellar evolution. We detect CCS, CCCS, HC
3
N, HC
5
N, l-C
3
H, and C
4
H toward 88%, 38%, 75%, 31%, 81%, and 88% of sources, respectively. Derived column densities for each molecule vary by one to two orders of magnitude across the sample. As derived from survival analysis, median column densities range between 1.2 × 10
11
cm
−2
(CCCS) and 1.5 × 10
13
cm
−2
(C
4
H), and estimated fractional abundances with respect to hydrogen range between 2 × 10
−13
(CCCS) and 5 × 10
−11
(C
4
H), which are low compared to cold cloud cores, warm carbon chain chemistry (WCCC) sources, and protostellar model predictions. We find significant correlations between molecules of the same carbon chain families, as well as between the cyanopolyynes (HC
n
N) and the pure hydrocarbon chains (C
n
H). This latter correlation is explained by a closely related production chemistry of C
n
H and cyanopolyynes during low-mass star formation.
Abstract
UV photochemistry in the surface layers of protoplanetary disks dramatically alters their composition relative to previous stages of star formation. The abundance ratio CN/HCN has long been ...proposed to trace the UV field in various astrophysical objects; however, to date the relationship between CN, HCN, and the UV field in disks remains ambiguous. As part of the ALMA Large Program MAPS (Molecules with ALMA at Planet-forming Scales), we present observations of CN
N
= 1–0 transitions at 0.″3 resolution toward five disk systems. All disks show bright CN emission within ∼50–150 au, along with a diffuse emission shelf extending up to 600 au. In all sources we find that the CN/HCN column density ratio increases with disk radius from about unity to 100, likely tracing increased UV penetration that enhances selective HCN photodissociation in the outer disk. Additionally, multiple millimeter dust gaps and rings coincide with peaks and troughs, respectively, in the CN/HCN ratio, implying that some millimeter substructures are accompanied by changes to the UV penetration in more elevated disk layers. That the CN/HCN ratio is generally high (>1) points to a robust photochemistry shaping disk chemical compositions and also means that CN is the dominant carrier of the prebiotically interesting nitrile group at most disk radii. We also find that the local column densities of CN and HCN are positively correlated despite emitting from vertically stratified disk regions, indicating that different disk layers are chemically linked. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.
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 = 88 − 77 and SiS J = 19 − 18 emission coincident with the position of a ∼ 2 MJup planet seen as a localized, Keplerian NIR feature within a gas-depleted, annular dust gap at ≈38 au. The SiS emission is located along an azimuthal arc and has a morphology similar to that of a known 12CO 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 12CO and 13CO 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 ≈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.
We present a three-dimensional kinematic reconstruction of the optically emitting, oxygen-rich ejecta of supernova remnant N132D in the Large Magellanic Cloud (LMC). Data were obtained with the 6.5 m ...Magellan telescope in combination with the IMACS+GISMO instrument and survey O iii λλ4959, 5007 line emission in a ∼3′ × 3′ region centered on N132D. The spatial and spectral resolutions of our data enable detailed examination of the optical ejecta structure. The majority of N132D's optically bright oxygen ejecta are arranged in a torus-like geometry tilted approximately 28° with respect to the plane of the sky. The torus has a radius of 4.4 pc (DLMC/50 kpc), exhibits a blueshifted radial velocity asymmetry of −3000 to +2300 km s−1, and has a conspicuous break in its circumference. Assuming homologous expansion from the geometric center of O-rich filaments, the average expansion velocity of 1745 km s−1 translates to an age since explosion of 2450 195 yr. A faint, spatially separated "runaway knot" (RK) with total space velocity of 3650 km s−1 is nearly perpendicular to the torus plane and coincident with X-ray emission that is substantially enhanced in Si relative to the LMC and N132D's bulk ejecta. These kinematic and chemical signatures suggest that the RK may have had its origin deep within the progenitor star. Overall, the main-shell morphology and high-velocity, Si-enriched components of N132D have remarkable similarity with those of Cassiopeia A, which was the result of a Type IIb supernova explosion. Our results underscore the need for further observations and simulations that can robustly reconcile whether the observed morphology is dominated by explosion dynamics or shaped by interaction with the environment.
Abstract
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 ∼213–268 GHz pilot survey of millimeter continuum CO isotopologs 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 millimeter continuum images of HD 34282 suggest a faint, unresolved source ∼5.″0 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 millimeter continuum flux. Line flux ratios between CO 2–1 isotopologs 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 the disk dust mass. Lower HCO
+
3–2 flux ratios may reflect lower ionization in Herbig AeBe/F disks. Lower 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.
Abstract
Here we present high-resolution (15–24 au) observations of CO isotopologue lines from the Molecules with ALMA on Planet-forming Scales (MAPS) ALMA Large Program. Our analysis employs ...observations of the (
J
= 2–1) and (1–0) lines of
13
CO and C
18
O and the (
J
= 1–0) line of C
17
O for five protoplanetary disks. We retrieve CO gas density distributions, using three independent methods: (1) a thermochemical modeling framework based on the CO data, the broadband spectral energy distribution, and the millimeter continuum emission; (2) an empirical temperature distribution based on optically thick CO lines; and (3) a direct fit to the C
17
O hyperfine lines. Results from these methods generally show excellent agreement. The CO gas column density profiles of the five disks show significant variations in the absolute value and the radial shape. Assuming a gas-to-dust mass ratio of 100, all five disks have a global CO-to-H
2
abundance 10–100 times lower than the interstellar medium ratio. The CO gas distributions between 150 and 400 au match well with models of viscous disks, supporting the long-standing theory. CO gas gaps appear to be correlated with continuum gap locations, but some deep continuum gaps do not have corresponding CO gaps. The relative depths of CO and dust gaps are generally consistent with predictions of planet–disk interactions, but some CO gaps are 5–10 times shallower than predictions based on dust gaps. This paper is part of the MAPS special issue of the Astrophysical Journal Supplement.
Abstract
We report the detection of more than 120 emission lines corresponding to eight complex organic molecules (COMs; CH
3
OH, CH
3
CH
2
OH, CH
3
OCH
3
, CH
3
OCHO, CH
3
COCH
3
, NH
2
CHO, CH
2
...DCN, and CH
3
CH
2
CN) and three isotopologues (CH
2
DOH,
13
CH
3
CN, and CH
3
C
15
N) toward the western component of the Ser-emb 11 binary young stellar object 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 H
2
CO and CH
3
OH emission in a nearby millimeter source that had not been previously cataloged. 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.
PDF
