On the distance of the high latitude dark cloud Lynds 134 in Serpens

Straižys, V.; Cernis, K.; Kazlauskas, A.; Meistas, E.

doi:10.1515/astro-1992-0203

Cited by 57 publications

(92 citation statements)

References 9 publications

(12 reference statements)

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“…A number of spectra show absorption against the continuum in addition to self-absorption. In the cases where these Chen et al (2008); (7) Seidensticker & Schmidt-Kaler (1989); (8) Fuller et al (1995); (9) Hogerheijde et al (1999); (10) Eiroa et al (2008); (11) Jørgensen et al (2002); (12) Goldsmith & Sernyak (1984); (13) Frerking et al (1987); (14) Straizys et al (1992); (15) observations were done as dual-beam-switch (DBS) the data reduction was redone, and the level-1 reference-position data examined for emission. None of the DBS reference spectra shows emission, and thus the absorption is believed to be intrinsic to the source.…”

Section: Herschel-hifi Observationsmentioning

confidence: 99%

Water in star-forming regions withHerschel(WISH)

Kristensen

Dishoeck

Bergin

et al. 2012

A&A

254

589

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Context. Water is a key tracer of dynamics and chemistry in low-mass star-forming regions, but spectrally resolved observations have so far been limited in sensitivity and angular resolution, and only data from the brightest low-mass protostars have been published. Aims. The first systematic survey of spectrally resolved water emission in 29 low-mass (L < 40 L ) protostellar objects is presented. The sources cover a range of luminosities and evolutionary states. The aim is to characterise the line profiles to distinguish physical components in the beam and examine how water emission changes with protostellar evolution. Methods. H 2 O was observed in the ground-state 1 10 -1 01 transition at 557 GHz (E up /k B ∼ 60 K) as single-point observations with the Heterodyne Instrument for the Far-Infrared (HIFI) on Herschel in 29 deeply embedded Class 0 and I low-mass protostars. Complementary far-IR and sub-mm continuum data (including PACS data from our programme) are used to constrain the spectral energy distribution (SED) of each source. H 2 O intensities are compared to inferred envelope properties, e.g., mass and density, outflow properties and CO 3-2 emission. Results. H 2 O emission is detected in all objects except one (TMC1A). The line profiles are complex and consist of several kinematic components tracing different physical regions in each system. In particular, the profiles are typically dominated by a broad Gaussian emission feature, indicating that the bulk of the water emission arises in outflows, not in the quiescent envelope. Several sources show multiple shock components appearing in either emission or absorption, thus constraining the internal geometry of the system. Furthermore, the components include inverse P-Cygni profiles in seven sources (six Class 0, one Class I) indicative of infalling envelopes, and regular P-Cygni profiles in four sources (three Class I, one Class 0) indicative of expanding envelopes. Molecular "bullets" moving at > ∼ 50 km s −1 with respect to the source are detected in four Class 0 sources; three of these sources were not known to harbour bullets previously. In the outflow, the H 2 O/CO abundance ratio as a function of velocity is nearly the same for all line wings, increasing from 10 −3 at low velocities (<5 km s −1 ) to > ∼ 10 −1 at high velocities (>10 km s −1 ). The water abundance in the outer cold envelope is low, > ∼ 10 −10 . The different H 2 O profile components show a clear evolutionary trend: in the younger Class 0 sources the emission is dominated by outflow components originating inside an infalling envelope. When large-scale infall diminishes during the Class I phase, the outflow weakens and H 2 O emission all but disappears.

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Section: Herschel-hifi Observationsmentioning

confidence: 99%

Water in star-forming regions withHerschel(WISH)

Kristensen

Dishoeck

Bergin

et al. 2012

A&A

254

589

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“…17). Straižys et al (1992) estimated a distance of 288 ± 25 pc to the L1167/1174 again by taking an average distance of four considerably reddened stars. They proposed a distance of 275 pc to HD 200775, which is The dashed vertical lines are drawn at 168 pc, 310 pc, and 408 pc inferred from the procedure described in Sect.…”

Section: L1148mentioning

confidence: 99%

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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“…We used the stars from F1 alone as the situation is much more complex towards F2. The most widely quoted distances to LDN 1167/1174 or the NGC 7023 and LDN 1147/1158 (clouds located ∼2 • west of NGC 7023) groups are 288 ± 25 and 325 ± 13 pc respectively (Straižys et al 1992). They used the Vilnius photometric system to classify the stars and also to get the interstellar reddening.…”

Section: Ngc 7023mentioning

confidence: 99%

A method to determine distances to molecular clouds using near-IR photometry

Maheswar

Lee²,

Bhatt

et al. 2010

A&A

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Aims. We aim to develop a method to determine distances to molecular clouds using JHK near-infrared photometry. Methods. The method is based on a technique that aids spectral classification of stars lying towards the fields containing the clouds into main sequence and 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.Results. We applied the method to four clouds, L1517, Chamaeleon I, Lupus 3 and NGC 7023 and estimated their distances as 167 ± 30, 151 ± 28, 157 ± 29 and 408 ± 76 pc respectively, which are in good agreement with the previous distance estimations available in the literature.

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On the distance of the high latitude dark cloud Lynds 134 in Serpens

Cited by 57 publications

References 9 publications

Water in star-forming regions withHerschel(WISH)

Water in star-forming regions withHerschel(WISH)

Distances to dense cores that contain very low luminosity objects

A method to determine distances to molecular clouds using near-IR photometry

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