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Register a new userHCN $J$=4-3, HNC $J$=1-0, $mathrm{H^{13}CN}$ $J$=1-0, and $mathrm{HC_3N}$ $J$=10-9 Maps of Galactic Center Region I: Spatially-Resolved Measurements of Physical Conditions and Chemical Composition
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This {it supplement} paper presents the maps of HCN $J$=4-3, HNC $J$=1-0, $mathrm{H^{13}CN}$ $J$=1-0, and HC$_3$N $J$=10-9 for the Galactic central molecular zone (CMZ), which have been obtained using the Atacama Submillimeter Telescope Experiment and Nobeyama Radio Observatory 45-m telescope. Three-dimensional maps (2-D in space and 1-D in velocity) of the gas kinetic temperature ($T_mathrm{kin}$), hydrogen volume density ($n_mathrm{H_2}$), and fractional abundances of eight molecules (HCN, HNC, $mathrm{HC_3N}$, HCO$^+$, $mathrm{H_2CO}$, SiO, CS, and $mathrm{N_2H^+}$) have been constructed from our and archival data. We have developed a method with hierarchical Bayesian inference for this analysis, which has successfully suppressed the artificial correlations among the parameters created by systematic errors due to the deficiency in the simple one-zone excitation analysis and the calibration uncertainty. The typical values of $T_mathrm{kin}$ and $n_mathrm{H_2}$ are $10^{1.8} $K and $10^{4.2} mathrm{cm}^{-3}$, respectively, and the presence of an additional cold/low-density component is also indicated. The distribution of high-temperature regions is poorly correlated with known active star-forming regions, while a few of them coincide with shocked clouds. Principal component analysis has identified two distinct groups in the eight analyzed molecules: one group with large PC1 and PC2 scores and the other with a large $T_mathrm{kin}$ dependence, which could be explained using two regimes of shock chemistry with fast ($gtrsim 20 mathrm{km,s}^{-1}$) and slow ($lesssim 20 mathrm{km,s}^{-1}$) velocity shocks, respectively. This supports the idea that the mechanical sputtering of dust grains and the mechanical heating play primary roles in the chemical and thermal processes in CMZ clouds.
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We report a statistical analysis exploring the origin of the overall low star formation efficiency (SFE) of the Galactic central molecular zone (CMZ) and the SFE diversity among the CMZ clouds using a wide-field HCN $J$=4-3 map, whose optically thin critical density ($sim10^7,mathrm{cm}^{-3}$) is the highest among the tracers ever used in CMZ surveys. Logistic regression is performed to empirically formulate star formation probability of 195 HCN clumps, 13 of which contain star formation signatures. The explanatory parameters in the best-fit model are reduced into the virial parameter $alpha_{mathrm{vir}}$ without significant contribution from other parameters, whereas the performance of the model without $alpha_{mathrm{vir}}$ is no better than that using randomly generated data. The threshold $alpha_{mathrm{vir}}$ is 6, which translates into a volume density ($n_{mathrm{H_2}}$) of $10^{4.6},mathrm{cm}^{-3}$ with the $n_{mathrm{H_2}}$-$alpha_{mathrm{vir}}$ correlation. The scarcity of the low-$alpha_{mathrm{vir}}$ clumps, whose fraction to all HCN clumps is 0.1, can be considered as one of the immediate causes of the suppressed SFE. No correlation between the clump size or mass and star formation probability is found, implying that HCN $J$=4-3 does not immediately trace the mass of star-forming gas above a threshold density. Meanwhile, star-forming and non-star-forming clouds are degenerate in the physical parameters of the CS $mathit{J}$=1-0 clouds, highlighting the efficacy of the HCN $mathit{J}$=4-3 line to probe star-forming regions in the CMZ. The time scale of the high-$alpha_{mathrm{vir}}$ to low-$alpha_{mathrm{vir}}$ transition is $lesssim2$ Myr, which is consistent with the tidal compression and X1/X2 orbit transition models but possibly does not fit the cloud-cloud collision picture.
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The disk around HD 142527 attracts a lot of attention, amongst others because of its resolved (sub) mm dust continuum that is concentrated into a horseshoe-shape towards the north of the star. In this manuscript we present spatially resolved ALMA detections of the HCN J=4-3 and CS J=7-6 emission lines. These lines give us a view deeper into the disk compared to the (optically thicker) CO isotopes. This is the first detection of CS J=7-6 coming from a protoplanetary disk. Both emission lines are azimuthally asymmetric and are suppressed under the horseshoe-shaped continuum emission peak. A possible mechanism to explain the decrease under the horseshoe-shaped continuum is the increased opacity coming from the higher dust concentration at the continuum peak. Lower {gr dust and/or gas} temperatures and an optically thick radio-continuum reduce line emission by freeze-out and shielding of emission from the far side of the disk.
We present a formalism that extends the Majorana-construction to arbitrary spin (j,0)+(0,j) representation spaces. For the example case of spin-1, a wave equation satisfied by the Majorana-like (1,0)+(0,1) spinors is constructed and its physical content explored. The (j,0)+(0,j) Majorana-construct is found to possess an unusual classical and quantum field theoretic structure. Relevance of our formalism to parity violation, hadronic phenomenologies, and grand unified field theories is briefly pointed out.
A survey of C2H N=1-0 and N2H+ J=1-0 toward Planck Galactic cold clumps (PGCCs) was performed using the Purple Mountain Observatorys 13.7 m telescope. C2H and N2H+ were chosen to study the chemical evolutionary states of PGCCs. Among 121 observed molecular cores associated with PGCCs, 71 and 58 are detected with C2H N=1-0 and N2H+ J=1-0, respectively. The detected lines of most sources can be fitted with a single component with compatible Vlsr and line widths, which confirms that these PGCC cores are very cold (with gas temperatures 9-21 K) and quiescent while still dominanted by turbulence. The ratio between the column densities of C2H and N2H+ (N(C2H)/N(N2H+)) is found to be a good tracer for the evolutionary states of PGCC cores. Gas-grain chemical model can reproduce the decreasing trend of N(C2H)/N(N2H+) as a function of time. The cores with the lowest abundances of N2H+ (X[N2H+] < 10^{-10}) are the youngest, and have nearly constant abundances of C2H. In evolved cores with X[N2H+] ~ 1E-9, abundances of C2H drop quickly as the exhaustion of carbon atoms. Although these PGCC cores are in different evolutionary states, they are all quite young (<5E5 yr) with N(C2H) > N(N2H+). Mapping observations are carried out toward 20 PGCC cores. The PGCC cores in Cepheus have lower N(C2H)/N(N2H+) and larger line widths compared with those in Taurus. This implies that PGCC cores in Taurus are less chemically evolved than those in Cepheus.
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