2021May.md~

## 2021 May
### May 3  
#### [High Spatial Resolution Observations of Molecular Lines towards the Protoplanetary Disk around TW Hya with ALMA](https://arxiv.org/abs/2105.00976)
- # TW Hya
- method:
	- ALMA 9 au observations. 
- progress:
	- A model with either CO gas depletion or depletion of gas-phase oxygen elemental abundance is required to reproduce the relatively weak CO isotopologue line intensities observed in the outer disk, consistent with previous atomic and molecular line observations towards the TW Hya disk.

#### [Linking ice and gas in the Lambda Orionis Barnard 35A cloud](https://arxiv.org/abs/2105.00652)
- # ice and gas
- Question:
	- How some of these solid-state molecules are converted into gas-phase species is still a matter of debate. 
- Aim:
	- Our aim is to directly compare ice and gas abundances of methanol (CH3OH) and CO, and to investigate the relationship between ice and gas in low-mass protostellar envelopes. 
- method:
	- ALMA IRAS05417+0907 in B35A.
- Progress:
	- A discrepancy between submillimeter dust emission and H2O ice column density is found for B35A−4 and B35A−5

#### [870 Micron Dust Continuum of the Youngest Protostars in Ophiuchus](https://arxiv.org/abs/2105.00514)
- # Ophiuchus
- progress:
	- The multiplicity fraction (MF) and companion star fraction (CSF) of the combined Class I and Flats based solely on this work is 0.25 ± 0.09 and 0.33 ± 0.10. We posit there are some differences in the conditions for star formation in Ophiuchus that strongly affects disk size (and consequently disk mass), but does not affect system multiplicity, which could imply important variation in planet formation processes.

#### [Transport of Protostellar Cosmic Rays in Turbulent Dense Cores](https://arxiv.org/abs/2105.00028)
- # cosmic rays # dense cores
- progress:
	- the CR flux is focused in the direction of the outflow cavity, creating a 'flashlight' effect and allowing CRs to leak out of the core.

#### [Revealing the Physical Conditions around Sgr A* using Bayesian Inference -- I. Observations and Radiative Transfer](https://arxiv.org/abs/2105.00042)
- # Sgr A* 
- Progress:
	- 272-375 GHz toward Sgr A CND. We also determine that the total gas mass contained within the CND is M ≈4×104 M⊙. Furthermore, we qualitatively note that the observed chemical enrichment across large scales within the CND is consistent with bulk grain processing.

#### [Spectroscopic detection of complex nitrile species ethyl cyanide in the high mass star formation region IRAS 18566+0408](https://arxiv.org/abs/2105.01421)
- # IRAS 18566+0408 # hot cores
- Progress:
	- ALMA results suggest that the statistical column density of ethyl cyanide (CH3CH2CN) is 3.42×1015 cm−2 with rotational temperature Trot = 70 K.


#### [The ionized heart of a molecular disk. ALMA observations of the hyper-compact HII region G24.78+0.08 A1](https://arxiv.org/abs/2105.01516)
- # G24.78+0.08 A1 # HCHII
- Progress: 
	- This is the first example of a molecular disk around a high-mass forming star that, while becoming internally ionized after the onset of the HII region, continues to accrete mass onto the ionizing star.

#### [Multi-frequency high spectral resolution observations of HCN toward the circumstellar envelope of Y CVn](https://arxiv.org/abs/2105.01411)
- # C-star # Y CYn
- Progress:
	- HCN is rotationally and vibrationally out of LTE throughout the whole envelope. Our analysis finds a total HCN column density that ranges from ~2.1E+18 to 3.5E+18 cm^{-2}, an abundance with respect to H2 of 3.5E-05 to 1.3E-04, and a 12C/13C isotopic ratio of ~2.5 throughout the whole envelope.

#### [ALMA view of the ρ Ophiuchi A PDR with a 360-au beam: the [CI] emission originates from the plane-parallel PDR and extended gas](https://arxiv.org/abs/2104.06030)
- # rho Ophiuchi A # PDR # CI
- Questions: plane-parallel PDR model or clumpy PDR model?
- Method: ALMA. If the clumpy PDR model is the case, observations with high spatial resolution should be able to identify clumpy structures and reveal differences between the spatial distributions of [CI] and CO. 
- Progress:
	- We found that the 4.5 μm emission, C0, and CO are distributed in this order from the excitation star (S1) in a complementary pattern. These results indicate that [CI] is emitted from a thin layer in the PDR generated by the excitation star, as predicted in the plane-parallel PDR model. Extended [CI] emission was also detected, which shows nearly uniform integrated intensity over the entire field-of-view. The line profile of the extended component is different from that of the above shell component.
- Note:  These results suggest that [CI] is emitted also from the extended gas with a density of nH2∼10^3 cm−3, which is not greatly affected by the excitation star.


#### [The complex organic molecular content in the L1498 starless core](https://arxiv.org/abs/2105.08363)
- # L1498 # COM
- Questions:
	- Observations carried out toward starless and pre-stellar cores have revealed that complex organic molecules are prevalent in these objects, but it is unclear what chemical processes are involved in their formation. Recently, it has been shown that complex organics are preferentially produced at an intermediate-density shell within the L1544 pre-stellar core at radial distances of ~4000 au with respect to the core center. However, the spatial distribution of complex organics has only been inferred toward this core and it remains unknown whether these species present a similar behaviour in other cores. 
- Progress:
	- Similarly to L1544, our observations reveal that small O-bearing molecules and N-bearing species are enhanced by factors ~4-14 toward the outer shell of L1498. However, unlike L1544, large O-bearing organics such as CH3CHO, CH3OCH3 or CH3OCHO are not detected within our sensitivity limits. For N-bearing organics, these species are more abundant toward the outer shell of the L1498 pre-stellar core than toward the one in L1544.
- Possible solution:
  - We propose that the differences observed between O-bearing and N-bearing species in L1498 and L1544 are due to the different physical structure of these cores, which in turn is a consequence of their evolutionary stage, with L1498 being younger than L1544.
- Note:
  - This result encourages more studies of such starless cores with single-dish. This would lead to the discovery of source-by-source variations in their chemistry.

#### [Star Formation in a Strongly Magnetized Cloud](https://arxiv.org/abs/2101.01326)
- # Vela C # B field
- Progress:
  - Deuteration along the filament. N2H+/N2D+. Strong B field.

#### [Water Production Rates from SOHO/SWAN Observations of Six comets: 2017-2020](https://arxiv.org/abs/2105.06565)
- # water # comets
- Progress:
  - The water production rates of six comets from the Oort Cloud, C/2015 V2 (Johnson), C/2019 Y1 (ATLAS), C/2017 T2 (PanSTARRS), C/2020 F8 (SWAN), C/2019 Y4 (ATLAS), and C/2019 U6 (Lemmon).


#### [First survey of HCNH+ in high-mass star-forming cloud cores](https://arxiv.org/abs/2105.08732)
- # HCNH+ # high-mass star formation
- Question:
  - The molecular ion HCNH+ is thought to be a crucial species in ion-neutral astrochemical reactions, but so far it has been detected only in a handful of star-forming regions, and hence its chemistry is poorly known. 
- Progress:
  - The fractional abundances of HCNH+, [HCNH+], w.r.t. H2, are in the range 0.9 - 14e-11, and the highest values are found towards cold starless cores. The abundance ratios [HCNH+]/[HCN] and [HCNH+]/[HCO+] are both < 0.01 for all objects except for four starless cores, for which they are well above this threshold. Our predictions indicate that in the warm model HCNH+ is mainly produced by reactions with HCN and HCO+, while in the cold one the main progenitor species of HCNH+ are HCN+ and HNC+.
- Note:
  - The chemistry of HCNH+ is different in cold/early and warm/evolved cores. They propose that the abundance ratios [HCNH+]/[HCN] and [HCNH+]/[HCO+] is a useful astrochemical tool to discriminate between different evolutionary phases in the process of star formation.

#### [A study of 90 GHz dust emissivity on molecular cloud and filament scales](https://arxiv.org/abs/2105.13432)
- # dust # MUSTANG2 # Orion A # Orion B # Serpens-S
- Progress:
  - . These data also show an excess of emission at 3mm, though somewhat weaker (8.5% excess) compared to what is seen at higher resolution

#### [The Core Mass Function Across Galactic Environments. III. Massive Protoclusters](https://arxiv.org/abs/2104.08861)
- # CMF # IMF
- Question:
  - The stellar initial mass function (IMF) is fundamental for many areas of astrophysics, but its origin remains poorly understood. It may be inherited from the core mass function (CMF) or arise as a result of more chaotic, competitive accretion.
- Progress:
  -  we find evidence of a break in this power-law behavior between ∼5 and 15M⊙, which is, to our knowledge, the first time such a break has been found in distant (>1 kpc) regions by ALMA. The massive protocluster CMF is significantly different, indicating the role of environment dependence.

#### [A multi-line study of the filamentary infrared dark cloud G351.78-0.54](https://arxiv.org/abs/2105.03133)
- # G351.78-0.54 # filament
- Progress:
  -  The velocity shift of the higher excitation HNCO lines may indicate a movement of the hot core relative the surrounding medium.

#### [Detection of Interstellar H2CCCHC3N](https://arxiv.org/abs/2105.03347)
- # TMC1
- Question:
  - The chemical pathways linking the small organic molecules commonly observed in molecular clouds to the large, complex, polycyclic species long-suspected to be carriers of the ubiquitous unidentified infrared emission bands remain unclear.
- Progress:
  - Cyanoacetyleneallene may represent an intermediate between less-saturated carbon-chains, such as the cyanopolyynes, that are characteristic of cold cores and the more recently-discovered cyclic species like cyanocyclopentadiene. Results from our models show that the gas-phase allene-based formation route in particular produces abundances of H2CCCHC3N that match the column density of 2×1011 cm−2 obtained from the MCMC Source Model, and that the grain-surface route yields large abundances on ices that could potentially be important as precursors for cyclic molecules.

#### [The JCMT Gould Belt Survey: radiative heating by OB stars](https://arxiv.org/abs/2105.03353)
- # Dust temperature
- Progress: O-type stars produce the greatest clump average temperature rises and largest heating extent, with temperatures over 40 K and significant heating out to at least 2.4 pc. Early-type B stars (B4 and above) produce temperatures of over 20 K and significant heating over 0.4 pc. Late-type B stars show a marginal heating effect within 0.2 pc.

#### [Magnetohydrodynamic effect on first star formation: prestellar core collapse and protostar formation](https://arxiv.org/abs/2105.03430)
- # B field
- Progress:
  - Our results show that the thermal evolution of the central core is hardly affected by a magnetic field, because magnetic forces do not prevent the contraction along the fields lines. We also find that the magnetic braking extracts the angular momentum from the core and suppresses fragmentation depending on the initial strength of the magnetic field. The angular momentum transport by the magnetic outflows is less effective than that by the magnetic braking because the outflows are launched only in a late phase of the collapse.

#### [Chemical analysis of prestellar cores in Ophiuchus yields short timescales and rapid collapse](https://arxiv.org/abs/2105.02253)
- # Ophiuchus
- Question:
  - How the collapse proceeds and what are the main physical processes driving it, however, is still under debate and a final consensus on the timescale of the process has not been reached. Does this contraction proceed slowly, sustained by strong magnetic fields and ambipolar diffusion, or is it driven by fast collapse with gravity dominating the entire process?
- Progress:
  - APEX observations of ortho-H2D+ and para-D2H+ for six cores, providing a range of ages for the observed cores up to 200 kyr.


#### [Anisotropic Turbulence in Position-Position-Velocity Space: Probing Three-Dimensional Magnetic Fields](https://arxiv.org/abs/2104.02842)
- # Anisotropic turbulence # B field
- Progress:
  - Following the theoretical framework developed in Kandel et al. (2016), we find that the anisotropy in a given velocity channel is affected by the inclination angle between the 3D magnetic field direction and the line-of-sight as well as media magnetization. We analyze the synthetic PPV cubes generated by incompressible and compressible MHD simulations. We confirm that the PPV channel's intensity fluctuations measured in various position angles reveal plane-of-the-sky magnetic field orientation. We show that by varying the channel width, the anisotropies of the intensity fluctuations in PPV space can be used to simultaneously estimate both magnetic field inclination angle and strength of total magnetic fields.
- Note:
  - This would be very useful to determine 3D B field using spectral line observations.

#### [Multi-scale Magnetic Fields in the Central Molecular Zone: Inference from the Gradient Technique](https://arxiv.org/abs/2105.03605)
- # CMZ # B field
- Progress:
  -  They map the wavelength-dependent magnetic field orientation across the central molecular zone, including close-ups of the Radio Arc and Sagittarius A West regions, on multi scales from ~0.1 pc to 10 pc.


#### [Where infall meets outflows: turbulent dissipation probed by CH+ and Lyα in the starburst/AGN galaxy group SMM J02399−0136 at z∼2.8](https://arxiv.org/abs/2105.10202)
- # CH+
- Progress:
  - CH+ in high-z galaxies. trace the total mass.

#### [ATOMS:ALMA Three-millimeter Observations of Massive Star-forming regions -- III :Catalogues of candidate hot molecular cores and Hyper/Ultra compact HII regions](https://arxiv.org/abs/2105.03554)
- # Massive Star-forming regions
- Progress:
  - We have identified 453 compact dense cores in 3 mm continuum emission maps in the ATOMS (ALMA Three-millimeter Observations of Massive Star-forming regions) survey, and compiled three catalogues of high-mass star forming cores. One catalogue, referred to as H/UC-HII catalogue, includes 89 cores that enshroud hyper/ultra compact (H/UC) HII regions as characterized by associated compact H40alpha emission. A second catalogue, referred to as pure s-cHMC, includes 32 candidate Hot Molecular Cores (HMCs) showing rich spectra (N>20lines) of complex organic molecules (COMs) but not associated with H/UC-HII regions. The third catalogue, referred to as pure w-cHMC, includes 58 candidate HMCs with relatively low levels of COM richness and not associated with H/UC-HII regions.
- Note:
  - The classification can be used to distinguish different classes, and investigate environment-dependent physics and chemistry.

#### [[CII] 158μm line emission from Orion A. I. A template for extragalactic studies?](https://arxiv.org/abs/2105.03735)
- # Orion A # [CII]
- Progress:
  - We find that, at the mapped spatial scales, predictions of the star-formation rate from [CII] emission underestimate the star-formation rate calculated from YSO counts in the Orion Nebula complex by an order of magnitude. [CII] emission from the Orion Nebula complex arises dominantly in the cloud surfaces, many viewed in edge-on geometry. [CII] emission from extended faint cloud surfaces may contribute significantly to the total [CII] emission on galactic scales.
- Note:
  - [CII] may not be able to trace the SFR faithfully.


#### [Convergent Filaments Contracting Towards an Intermediate-mass Prestellar Core](https://arxiv.org/abs/2105.04116)
- # Orion A
- Progress:
  - Filament contraction. The filaments also exhibit a possible fragmentation, but it does not seem to largely interrupt the gas structure or the infall motion towards the center. MMS-7 thus provides an example of filamentary infall into an individual prestellar core. The filament contraction could be less intense but more steady than the global spherical collapse, and may help generate an intermediate- or even high-mass star.

#### [ALMA Observations toward the S-shaped Outflow and the Envelope around NGC1333 IRAS 4A2](https://arxiv.org/abs/2105.04224)
- # NGC 1333
- progress:
  - The observed features are reproduced by the magnetohydrodynamic simulation of the collapsing core whose magnetic field direction is misaligned to the rotational axis. Our simulation shows that the intensity of the outflow lobes is enhanced on one side, resulting in the formation of S-shaped morphology. The S-shaped outflow can also be explained by the precessing outflow launched from an unresolved binary with a separation larger than 12 au (0.04arcsec). Additionally, we discovered a previously unknown extremely high velocity component at ∼45-90 km/s near IRAS 4A2 with CO.


#### [Detection of a 20 minute time lag observed from Sgr A* between 8 and 10 GHz with the VLA](https://arxiv.org/abs/2105.11473)
- # Sgr A*
- Progress:
  - They report the detection and analysis of a radio flare observed on 17 April 2014 from Sgr A* at 9 GHz using the VLA in its A-array configuration. We cross correlate the lowest and highest spectral windows centered at 8.0 and 9.9 GHz, respectively, and find the 8.0 GHz light curve lagging 18.37+2.17−2.18 minutes behind the 9.9 GHz light curve. The properties of this flare are consistent with a transient warm spot in the accretion flow at a distance of 10-100 Schwarzschild radii from Sgr A*.