Metsähovi MM-wave observations of interstellar clouds and SiO masers

Harju, J.; Harjunpaa, P.; Liljeström, T.; Mattila, K.; Solasaari, J.; Toriseva, M.

doi:10.1007/bfb0119458

Cited by 6 publications

(7 citation statements)

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“…Similar distance and proper motion values shown by all the three YSOs indicate that they are spatially and kinematically associated with each other and that the complex is also located at a distance of 340 ± 3 pc from us. Similar values of V lsr (≈ 2.6 km s −1 ) shared by the individual clouds of the complex (Harjunpaa et al 1991;Yonekura et al 1997;Suzuki et al 2014) also supports the above argument. Straizys et al (1992), based on Vilnius photometry which gives two dimensional classification and extinction suffered by stars, estimated distances to the L1147/1158 cloud complex.…”

Section: Distance Of L1147/1158 Complexsupporting

confidence: 82%

Distance, magnetic field and kinematics of a filamentary cloud LDN 1157

Sharma,

Maheswar,

Soam

et al. 2020

Preprint

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Context. LDN 1157 is one of the several clouds situated in the cloud complex, LDN 1147/1158. The cloud presents a coma-shaped morphology with a well-collimated bipolar outflow emanating from a Class 0 protostar, LDN 1157-mm, residing deep inside the cloud. Aims. The main goals of this work are (a) to map the inter-cloud magnetic field (ICMF) geometry of the region surrounding LDN 1157 to investigate its relationship with the cloud morphology, with the outflow direction and with the core magnetic field (CMF) geometry inferred from the mm-and sub-mm polarization results from the literature, and (b) to investigate the kinematic structure of the cloud. Methods. We carried out optical (R-band) polarization observations of the stars projected on the cloud to map the parsec-scale magnetic field geometry and made spectroscopic observations of the entire cloud in 12 CO, C 18 O and N 2 H + (J=1-0) lines to investigate its kinematic structure. Results. We obtained a distance of 340±3 pc to the LDN 1147/1158, complex based on the Gaia DR2 parallaxes and proper motion values of the three young stellar objects (YSOs) associated with the complex. A single filament of ∼ 1.2 pc in length (traced by the Filfinder algorithm) and ∼ 0.09 pc in width (estimated using the Radfil algorithm) is found to run all along the coma-shaped cloud. Based on the relationships between the ICMF, CMF, filament orientations, outflow direction, and the presence of an hour-glass morphology of the magnetic field, it is likely that the magnetic field had played an important role in the star formation process in LDN 1157. LDN 1157-mm is embedded in one of the two high density peaks detected using the Clumpfind algorithm. Both the detected clumps are lying on the filament and show a blue-red asymmetry in the 12 CO line. The C 18 O emission is well correlated with the filament and presents a coherent structure in velocity space. Combining the proper motions of the YSOs and the radial velocity of LDN 1147/1158 and an another complex LDN 1172/1174 which is situated ∼ 2 • east of it, we found that both the complexes are moving collectively toward the Galactic plane. The filamentary morphology of the east-west segment of LDN 1157 may have formed as a result of mass lost by ablation due to the interaction of the moving cloud with the ambient interstellar medium.

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Section: Distance Of L1147/1158 Complexsupporting

confidence: 82%

Distance, magnetic field and kinematics of a filamentary cloud LDN 1157

Sharma,

Maheswar,

Soam

et al. 2020

Preprint

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“…L1155C-L1155C is a dense molecular condensation within a dark cloud L1158 in Cepheus. Harjunpää et al (1991) have observed this source in CO, 13 CO, C 18 O, HCO + , and NH 3 , and have found two cores with slightly different velocities. These authors suggest that the cores might be a bound pair.…”

Section: L1512-mentioning

confidence: 88%

A Survey for Infall Motions toward Starless Cores. II. CS (2–1) and N ₂ H ⁺ (1–0) Mapping Observations

Lee

Myers

Tafalla

2001

ASTROPHYS J SUPPL S

203

155

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We present the results of an extensive mapping survey of 'starless' cores in the optically thick line of CS(2-1) and the optically thin lines of N 2 H + (1 − 0) and C 18 O (1 − 0). The purpose of this survey was to search for signatures of extended inward motions. A total of 53 targets were observed in the three lines with the FCRAO 14m telescope. Thirty three regions were mapped in both CS and N 2 H + , and thirty seven well-defined N 2 H + cores have been identified. The N 2 H + emission is generally compact enough to find a peak, while the CS and C 18 O emissions are more diffuse. For each core, we have derived the normalized velocity difference (δV CS) between the thick CS and thin N 2 H + peak velocities. We define 10 'strong' and 9 'probable' infall candidates, based on δV CS analysis and on the spectral shapes of CS lines. From our analysis of the blue-skewed CS spectra and the δV CS parameter, we find typical infall radii of 0.06 − 0.14 pc. Also, using a simple two layer radiative transfer model to fit the profiles, we derive one-dimensional infall speeds, half of whose values lie in the range of 0.05 − 0.09 km s −1. These values are similar to those found in L1544 by Tafalla et al., and this result confirms that infall speeds in starless cores are generally faster than expected from ambipolar diffusion in a strongly sub-critical core. In addition, the observed infall regions are too extended to be consistent with the 'inside-out' collapse model applied to a very low-mass star. In the largest cores, the spatial extent of the CS spectra with infall asymmetry is larger than the extent of the N 2 H + core by a factor of 2 − 3. All these results suggest that extended inward motions are a common feature in starless cores, and that they could represent a necessary stage in the condensation of a star-forming dense core.

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“…Kun (1998) found that there are three dust components at characteristic distances of 200, 300, and 450 pc, based on a cumulative distribution of field star distance moduli in Wolf diagrams. A complex velocity structure was reported by Harjunpää et al (1991) towards the directions of the L1147/48, L1152, L1157, and L1155/58 cloud complexes. They identified two distinct velocity components in 13 CO and C 18 O line profiles.…”

Section: L1148mentioning

confidence: 96%

Distances to dense cores that contain very low luminosity objects

Maheswar

Lee

Dib

2011

A&A

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Aims. We estimate the distances to dense molecular cores that harbour very low luminosity objects (VeLLOs) detected by the Spitzer Space Telescope and attempt to confirm their VeLLO nature. Methods. The cloud distances are estimated using a near-IR photometric method. We use a technique that performs a spectral classification of stars lying towards the fields containing the clouds as either main-sequence stars or giants. In this technique, the observed (J − H) and (H − K s ) colours are dereddened simultaneously using trial values of A V and a normal interstellar extinction law. The best fit of the dereddened colours to the intrinsic colours giving a minimum value of χ 2 then yields the corresponding spectral type and A V for the star. The main-sequence stars, thus classified, are then utilized in an A V versus distance plot to bracket the cloud distances. The typical error in the estimation of distances to the clouds are found to be ∼18%. Results. We estimate distances to seven cloud cores, IRAM 04191, L1521F, BHR 111, L328, L673-7, L1014, and L1148 using the above method. These clouds contain VeLLO candidates. The estimated distances to the cores are found to be 127 ± 25 pc (IRAM 04191), 136 ± 36 pc (L1521F), 355 ± 65 pc (BHR 111), 217 ± 30 pc (L328), 240 ± 45 pc (L673-7), 258 ± 50 pc (L1014), and 301 ± 55 pc (L1148). We re-evaluated the internal luminosities of the VeLLOs discovered in these seven clouds using the distances estimated from this work. Except for L1014−IRS (L int = 0.15 L ), all other VeLLO candidates are found to be consistent with the definition of a VeLLO (L int ≤ 0.1 L ). In addition to the cores that harbour VeLLO candidates, we also obtained distances to the clouds L323, L675, L676, CB 188, L1122, L1152, L1155, L1157, and L1158, which are located in the directions of the above seven cores. Towards L1521F and L1148, we found evidence of multiple dust layers.

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Metsähovi MM-wave observations of interstellar clouds and SiO masers

Cited by 6 publications

References 0 publications

Distance, magnetic field and kinematics of a filamentary cloud LDN 1157

Distance, magnetic field and kinematics of a filamentary cloud LDN 1157

A Survey for Infall Motions toward Starless Cores. II. CS (2–1) and N ₂ H ⁺ (1–0) Mapping Observations

Distances to dense cores that contain very low luminosity objects

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Metsähovi MM-wave observations of interstellar clouds and SiO masers

Cited by 6 publications

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Distance, magnetic field and kinematics of a filamentary cloud LDN 1157

Distance, magnetic field and kinematics of a filamentary cloud LDN 1157

A Survey for Infall Motions toward Starless Cores. II. CS (2–1) and N 2 H + (1–0) Mapping Observations

Distances to dense cores that contain very low luminosity objects

Contact Info

Product

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A Survey for Infall Motions toward Starless Cores. II. CS (2–1) and N ₂ H ⁺ (1–0) Mapping Observations