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تسجيل مستخدم جديدAmmonia observations towards the Aquila Rift cloud complex
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We surveyed the Aquila Rift complex including the Serpens South and W40 region in the NH$_3$(1,1) and (2,2) transitions making use of the Nanshan 26-m telescope. The kinetic temperatures of the dense gas in the Aquila Rift complex range from 8.9 to 35.0K with an average of 15.3$pm$6.1K. Low gas temperatures associate with Serpens South ranging from 8.9 to 16.8K with an average 12.3$pm$1.7K, while dense gas in the W40 region shows higher temperatures ranging from 17.7 to 35.0K with an average of 25.1$pm$4.9 K. A comparison of kinetic temperatures against HiGal dust temperatures indicates that the gas and dust temperatures are in agreement in the low mass star formation region of Serpens South. In the high mass star formation region W40, the measured gas kinetic temperatures are higher than those of the dust. The turbulent component of the velocity dispersion of NH$_3$(1,1) is found to be positively correlated with the gas kinetic temperature, which indicates that the dense gas may be heated by dissipation of turbulent energy. For the fractional total-NH3 abundance obtained by a comparison with Herschel infrared continuum data representing dust emission we find values from 0.1 to 21$times 10^{-8}$ with an average of 6.9$(pm 4.5)times 10^{-8}$. Serpens South also shows a fractional total-NH3 abundance ranging from 0.2 to 21$times 10^{-8}$ with an average of 8.6($pm 3.8)times 10^{-8}$. In W40, values are lower, between 0.1 and 4.3$times 10^{-8}$ with an average of 1.6($pm 1.4)times 10^{-8}$. Weak velocity gradients demonstrate that the rotational energy is a negligible fraction of the gravitational energy. In W40, gas and dust temperatures are not strongly dependent on the projected distance to the recently formed massive stars. Overall, the morphology of the mapped region is ring-like, with strong emission at lower and weak emission at higher Galactic longitudes.
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(Abridged) Aims. In the present part of our survey we search for ammonia emitters in the Aquila rift complex which trace the densest regions of molecular clouds. Methods. From a CO survey carried out with the Delingha 14-m telescope we selected ~150
targets for observations in other molecular lines. Here we describe the mapping observations in the NH3(1,1) and (2,2) inversion lines of the first 49 sources performed with the Effelsberg 100-m telescope. Results. The NH3(1,1) and (2,2) emission lines are detected in 12 and 7 sources, respectively. Among the newly discovered NH3 sources, our sample includes the following well-known clouds: the starless core L694-2, the Serpens cloud Cluster B, the Serpens dark cloud L572, the filamentary dark cloud L673, the isolated protostellar source B335, and the complex star-forming region Serpens South. Angular sizes between 40 and 80 (~0.04-0.08 pc) are observed for compact starless cores but as large as 9 (~0.5 pc) for filamentary dark clouds. The measured kinetic temperatures of the clouds lie between 9K and 18K. From NH3 excitation temperatures of 3-8K we determine H2 densities with typical values of ~(0.4-4) 10^4 cm^-3. The masses of the mapped cores range between ~0.05 and ~0.5M_solar. The relative ammonia abundance, X= [NH3]/[H2], varies from 10^-7 to 5 10^-7 with the mean <X> = (2.7+/-0.6) 10^-7 (estimated from spatially resolved cores assuming the filling factor eta = 1). In two clouds, we observe kinematically split NH3 profiles separated by ~1 km/s. The splitting is most likely due to bipolar molecular outflows for one of which we determine an acceleration of <~ 0.03 km/s/yr. A starless core with significant rotational energy is found to have a higher kinetic temperature than the other ones which is probably caused by magnetic energy dissipation.
As part of the science demonstration phase of the Herschel mission of the Gould Belt Key Program, the Aquila Rift molecular complex has been observed. The complete ~ 3.3deg x 3.3deg imaging with SPIRE 250/350/500 micron and PACS 70/160 micron allows
a deep investigation of embedded protostellar phases, probing of the dust emission from warm inner regions at 70 and 160 micron to the bulk of the cold envelopes between 250 and 500 micron. We used a systematic detection technique operating simultaneously on all Herschel bands to build a sample of protostars. Spectral energy distributions are derived to measure luminosities and envelope masses, and to place the protostars in an M_env - L_bol evolutionary diagram. The spatial distribution of protostars indicates three star-forming sites in Aquila, with W40/Sh2-64 HII region by far the richest. Most of the detected protostars are newly discovered. For a reduced area around the Serpens South cluster, we could compare the Herschel census of protostars with Spitzer results. The Herschel protostars are younger than in Spitzer with 7 Class 0 YSOs newly revealed by Herschel. For the entire Aquila field, we find a total of ~ 45-60 Class 0 YSOs discovered by Herschel. This confirms the global statistics of several hundred Class~0 YSOs that should be found in the whole Gould Belt survey.
We present the results of a ~250 square degrees CO mapping (+26d<l<+50d and -5d<b<+5d) toward the Aquila Rift region at a spatial resolution of ~50 and a grid spacing of 30. The high dynamic range CO maps with a spectral resolution of ~0.2km/s displa
y highly structured molecular cloud (MC) morphologies with valuable velocity information, revealing complex spatial and dynamical features of the local molecular gas. In combination with the MWISP CO data and the Gaia DR2, distances of the main MC structures in the local ISM are well determined toward the Aquila Rift. We find that the total MC mass within 1 kpc is about >4.1x10^5 Msun in the whole region. In fact, the mass of the molecular gas is dominated by the W40 giant molecular cloud (GMC) at ~474 pc (~1.4x10^5 Msun) and the GMC complex G036.0+01.0 at ~560-670 pc (~2.0x10^5 Msun), while the MCs at ~220-260pc have gas masses of 10^2-10^3 Msun. Interestingly, an ~80pc long filamentary MC G044.0-02.5 at a distance of ~404 pc shows a systematic velocity gradient along and perpendicular to the major axis of the filament. The HI gas with the enhanced emission has the similar spatial morphologies and velocity features compared to the corresponding CO structure, indicating that the large-scale converging HI flows are probably responsible for the formation of the MC. Meanwhile, the long filamentary MC consists of many sub-filaments with the lengths ranging from ~0.5 pc to several pc, as well as prevalent networks of filaments in other large-scale local MCs.
The initial conditions of molecular clumps in which high-mass stars form are poorly understood. In particular, a more detailed study of the earliest evolutionary phases is needed. The APEX Telescope Large Area Survey of the whole inner Galactic disk
at 870 micron, ATLASGAL, has been conducted to discover high-mass star-forming regions at different evolutionary phases. Using the Parkes telescope, we observed the NH3 (1,1) to (3,3) inversion transitions towards 354 ATLASGAL clumps in the fourth quadrant. For a subsample of 289 sources, the N2H+ (1-0) line was measured with the Mopra telescope. We measured a median NH3(1,1) line width of about 2 km/s and rotational temperatures from 12 to 28 K with a mean of 18 K. For a subsample with detected NH3 (2,2) hyperfine components, we found that the commonly used method to compute the (2,2) optical depth from the (1,1) optical depth and the (2,2) to (1,1) main beam brightness temperature ratio leads to an underestimation of the rotational temperature and column density. A larger median virial parameter of about 1 is determined using the broader N2H+ line width than is estimated from the NH3 line width of about 0.5 with a general trend of a decreasing virial parameter with increasing gas mass. We found a warmer surrounding of ATLASGAL clumps than the surrounding of low-mass cores and smaller velocity dispersions in low-mass than high-mass star-forming regions. The NH3 (1,1) inversion transition of 49% of the sources shows hyperfine structure anomalies. The intensity ratio of the outer hyperfine structure lines with a median of 1.27+/-0.03 and a standard deviation of 0.45 is significantly higher than 1, while the intensity ratios of the inner satellites with a median of 0.9+/-0.02 and standard deviation of 0.3 and the sum of the inner and outer hyperfine components with a median of 1.06+/-0.02 and standard deviation of 0.37 are closer to 1.
We carried out mapping observations toward three nearby molecular clouds, Orion A, Aquila Rift, and M17, using a new 100 GHz receiver, FOREST, on the Nobeyama 45-m telescope. In the present paper, we describe the details of the data obtained such as
intensity calibration, data sensitivity, angular resolution, and velocity resolution. Each target contains at least one high-mass star-forming region. The target molecular lines were $^{12}$CO ($J = 1 - 0$), $^{13}$CO ($J = 1 - 0$), C$^{18}$O ($J = 1 - 0$), N$_2$H$^+$ ($J=1-0$), and CCS ($J_N=8_7-7_6$), with which we covered the density range of 10$^2$ cm$^{-3}$ to 10$^6$ cm$^{-3}$ with an angular resolution of $sim 20arcsec$ and a velocity resolution of $sim$ 0.1 km s$^{-1}$. Assuming the representative distances of 414 pc, 436 pc, and 2.1 kpc, the maps of Orion A, Aquila Rift, and M17 cover most of the densest parts with areas of about 7 pc $times$ 15 pc, 7 pc $times$ 7 pc, and 36 pc $times$ 18 pc, respectively. On the basis of the $^{13}$CO column density distribution, the total molecular masses are derived to be $3.86 times 10^4 M_odot$, $2.67 times 10^4 M_odot$, and $8.1times 10^5 M_odot$ for Orion A, Aquila Rift, and M17, respectively. For all the clouds, the H$_2$ column density exceeds the theoretical threshold for high-mass star formation of $gtrsim$ 1 g cm$^{-2}$, only toward the regions which contain current high-mass star-forming sites. For other areas, further mass accretion or dynamical compression would be necessary for future high-mass star formation. This is consistent with the current star formation activity. Using the $^{12}$CO data, we demonstrate that our data have enough capability to identify molecular outflows, and for Aquila Rift, we identify 4 new outflow candidates. The scientific results will be discussed in details in separate papers.
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