- ID:
- ivo://CDS.VizieR/J/ApJS/219/20
- Title:
- Outflows and bubbles in Taurus
- Short Name:
- J/ApJS/219/20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have identified outflows and bubbles in the Taurus molecular cloud based on the ~100deg^2^ Five College Radio Astronomy Observatory ^12^CO(1-0) and ^13^CO(1-0) maps and the Spitzer young stellar object catalogs. In the main 44deg^2^ area of Taurus, we found 55 outflows, of which 31 were previously unknown. We also found 37 bubbles in the entire 100deg^2^ area of Taurus, none of which had been found previously. The total kinetic energy of the identified outflows is estimated to be ~3.9x10^45^erg, which is 1% of the cloud turbulent energy. The total kinetic energy of the detected bubbles is estimated to be ~9.2x10^46^erg, which is 29% of the turbulent energy of Taurus. The energy injection rate from the outflows is ~1.3x10^33^erg/s, which is 0.4-2 times the dissipation rate of the cloud turbulence. The energy injection rate from bubbles is ~6.4x10^33^erg/s, which is 2-10 times the turbulent dissipation rate of the cloud. The gravitational binding energy of the cloud is ~1.5x10^48^erg, that is, 385 and 16 times the energy of outflows and bubbles, respectively. We conclude that neither outflows nor bubbles can provide sufficient energy to balance the overall gravitational binding energy and the turbulent energy of Taurus. However, in the current epoch, stellar feedback is sufficient to maintain the observed turbulence in Taurus.
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- ID:
- ivo://CDS.VizieR/J/ApJS/146/1
- Title:
- O VI absorption in FUSE survey
- Short Name:
- J/ApJS/146/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Far Ultraviolet Spectroscopic Explorer (FUSE) observations of the O VI {lambda}{lambda}1031.926, 1037.617 absorption lines associated with gas in and near the Milky Way, as detected in the spectra of a sample of 100 extragalactic targets and two distant halo stars. We combine data from several FUSE Science Team programs with guest observer data that were public before 2002 May 1. The sight lines cover most of the sky above Galactic latitude |b|>25{deg}, at lower latitude the ultraviolet extinction is usually too large for extragalactic observations.
- ID:
- ivo://CDS.VizieR/J/ApJS/146/125
- Title:
- O VI in the galactic halo
- Short Name:
- J/ApJS/146/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Far-Ultraviolet Spectroscopic Explorer (FUSE) spectra of 100 extragalactic objects and two distant halo stars are analyzed to obtain measures of O VI {lambda}{lambda}1031.93, 1037.62 absorption along paths through the Milky Way thick disk/halo.
- ID:
- ivo://CDS.VizieR/J/ApJ/899/55
- Title:
- Parameters of protoplanetary disks in 5 SFRs
- Short Name:
- J/ApJ/899/55
- Date:
- 14 Mar 2022 07:11:43
- Publisher:
- CDS
- Description:
- Spatial correlations among protoplanetary disk orientations carry unique information on physics of multiple-star formation processes. We select five nearby star-forming regions that comprise a number of protoplanetary disks with spatially resolved images with ALMA and Hubble Space Telescope, and we search for the mutual alignment of the disk axes. Specifically, we apply the Kuiper test to examine the statistical uniformity of the position angle (PA: the angle of the major axis of the projected disk ellipse measured counterclockwise from the north) distribution. The disks located in the star-forming regions, except the Lupus clouds, do not show any signature of the alignment, supporting the random orientation. Rotational axes of 16 disks with spectroscopic measurement of PA in the LupusIII cloud, a subregion of the Lupus field, however, exhibit a weak and possible departure from the random distribution at a 2{sigma} level, and the inclination angles of the 16 disks are not uniform as well. Furthermore, the mean direction of the disk PAs in the LupusIII cloud is parallel to the direction of its filament structure and approximately perpendicular to the magnetic field direction. We also confirm the robustness of the estimated PAs in the Lupus clouds by comparing the different observations and estimators based on three different methods, including sparse modeling. The absence of the significant alignment of the disk orientation is consistent with the turbulent origin of the disk angular momentum. Further observations are required to confirm/falsify the possible disk alignment in the Lupus III cloud.
- ID:
- ivo://CDS.VizieR/J/AJ/122/3155
- Title:
- Peculiar HI cloud near galactic plane
- Short Name:
- J/AJ/122/3155
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An H I cloud with a double-lobed structure and a radial velocity of +50km/s has been found near l=92{deg}, b=-4{deg} in a low-resolution H I survey carried out at the Dominion Radio Astrophysical Observatory (DRAO). This velocity is forbidden for circular Galactic rotation. Because of its unusual morphology and small variation in radial velocity over the cloud, further observations of the area were made with the DRAO Synthesis Telescope, both in the H I line and in the radio continuum. The cloud has dimensions of about 3.3{deg}x0.5{deg}, and has a morphology somewhat similar to high-velocity H I clouds (HVCs). Several possible associations with other objects are examined in this paper. A variable inverted-spectrum radio continuum source exists near the morphological center of the H I cloud. It is probably a rare example of a gigahertz peaked spectrum (GPS) extragalactic source having a peak above 5GHz. A luminous B star is found close to the peculiar H I cloud, and the cloud is also located near the center of an H I supershell, supposedly located at a distance of about 9kpc. Energetic and other considerations lead to the conclusion that the cloud is probably not related to the HVC phenomenon nor to any of the above objects but is a relic of a nearby (D~1kpc) supernova event, all other evidence of which has now dissipated. Maps of continuum radio emission (at 1420 and 408MHz) in the area around the cloud are presented, as well as lists of continuum radio sources. A few isolated high-velocity knots of H I emission have also been detected in the vicinity of the cloud.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A117
- Title:
- Perpendicular HF map to the Orion Bar
- Short Name:
- J/A+A/631/A117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The hydrogen fluoride (HF) molecule is seen in absorption in the interstellar medium (ISM) along many lines of sight. Surprisingly, it is observed in emission toward the Orion Bar, which is an interface between the ionized region around the Orion Trapezium stars and the Orion molecular cloud. We aim to understand the origin of HF emission in the Orion Bar by comparing its spatial distribution with other tracers. We examine three mechanisms to explain the HF emission: thermal excitation, radiative dust pumping, and chemical pumping. We used a Herschel/HIFI strip map of the HF J=1-0 line, covering 0.5' by 1.5' that is oriented perpendicular to the Orion Bar. We used the RADEX non-local thermodynamic equilibrium (non-LTE) code to construct the HF column density map. We use the Meudon PDR code to explain the morphology of HF. The bulk of the HF emission at 10km/s emerges from the CO-dark molecular gas that separates the ionization front from the molecular gas that is deeper in the Orion Bar. The excitation of HF is caused mainly by collisions with H2 at a density of 10^5^cm^-3^ together with a small contribution of electrons in the interclump gas of the Orion Bar. Infrared pumping and chemical pumping are not important. We conclude that the HF J=1-0 line traces CO-dark molecular gas. Similarly, bright photodissociation regions associated with massive star formation may be responsible for the HF emission observed toward active galactic nuclei.
- ID:
- ivo://CDS.VizieR/J/ApJ/793/132
- Title:
- Perseus cloud sources Gaussian parameters
- Short Name:
- J/ApJ/793/132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the Arecibo Observatory, we have obtained neutral hydrogen (HI) absorption and emission spectral pairs in the direction of 26 background radio continuum sources in the vicinity of the Perseus molecular cloud. Strong absorption lines were detected in all cases, allowing us to estimate spin temperature (T_s_) and optical depth for 107 individual Gaussian components along these lines of sight. Basic properties of individual H I clouds (spin temperature, optical depth, and the column density of the cold and warm neutral medium (CNM and WNM), respectively) in and around Perseus are very similar to those found for random interstellar lines of sight sampled by the Millennium H I survey. This suggests that the neutral gas found in and around molecular clouds is not atypical. However, lines of sight in the vicinity of Perseus have, on average, a higher total H I column density and the CNM fraction, suggesting an enhanced amount of cold H I relative to an average interstellar field. Our estimated optical depth and spin temperature are in stark contrast with the recent attempt at using Planck data to estimate properties of the optically thick H I. Only ~15% of lines of sight in our study have a column density weighted average spin temperature lower than 50 K, in comparison with >~85% of Planck's sky coverage. The observed CNM fraction is inversely proportional to the optical depth weighted average spin temperature, in excellent agreement with the recent numerical simulations by Kim et al. (2014ApJ...786...64K). While the CNM fraction is, on average, higher around Perseus relative to a random interstellar field, it is generally low, between 10%-50%. This suggests that extended WNM envelopes around molecular clouds and/or significant mixing of CNM and WNM throughout molecular clouds are present and should be considered in the models of molecule and star formation. Our detailed comparison of H I absorption with CO emission spectra shows that only 3 of the 26 directions are clear candidates for probing the CO-dark gas as they have N(H I)>10^21^/cm2 yet no detectable CO emission.
- ID:
- ivo://CDS.VizieR/J/A+A/587/A106
- Title:
- Perseus dust optical depth and column density maps
- Short Name:
- J/A+A/587/A106
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical depth and temperature maps of the Perseus molecular cloud, obtained combining dust emission data from the Herschel and Planck satellites and 2MASS/NIR dust extinction maps. The maps have a resolution of 36~arcsec in the Herschel regions, and of 5~arcmin elsewhere. The dynamic range of the optical depth map ranges from 1x10^-2^mag up to 20mag in the equivalent K band extinction. We also evaluate the ratio between the SI2.2{mu} extinction coefficient and the SI850{mu} opacity. The value we obtain is close to the one found in the Orion B molecular cloud. We show that the cumulative and the differential area function of the data (which is proportional to the probability distribution function of the cloud column density) follow power laws with index respectively ~=-2, and ~=-3. We use WISE data to improve current YSO catalogs based mostly on Spitzer data and we build an up-to-date selection of Class I/0 objects. Using this selection, we evaluate the local Schmidt law, {Sigma}_YSO{prop.to}{Sigma}_gas_^{beta}^, showing that {beta}=2.4+/-0.6. Finally, we show that the area-extinction relation is important for determining the star formation rate in the cloud, which is in agreement with other recent works.
- ID:
- ivo://CDS.VizieR/J/ApJS/236/51
- Title:
- PGCCs in lambda Orionis complex. II. Cores at 850um
- Short Name:
- J/ApJS/236/51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on the 850{mu}m dust continuum data from SCUBA-2 at James Clerk Maxwell Telescope (JCMT), we compare overall properties of Planck Galactic Cold Clumps (PGCCs) in the {lambda} Orionis cloud to those of PGCCs in the Orion A and B clouds. The Orion A and B clouds are well-known active star-forming regions, while the {lambda} Orionis cloud has a different environment as a consequence of the interaction with a prominent OB association and a giant HII region. PGCCs in the {lambda} Orionis cloud have higher dust temperatures (T_d_=16.13+/-0.15K) and lower values of dust emissivity spectral index ({beta}=1.65+/-0.02) than PGCCs in the Orion A (T_d_=13.79+/-0.21K, {beta}=2.07+/-0.03) and Orion B (T_d_=13.82+/-0.19K, {beta}=1.96+/-0.02) clouds. We find 119 substructures within the 40 detected PGCCs and identify them as cores. Out of a total of 119 cores, 15 cores are discovered in the {lambda} Orionis cloud, while 74 and 30 cores are found in the Orion A and B clouds, respectively. The cores in the {lambda} Orionis cloud show much lower mean values of size R=0.08pc, column density N(H_2_)=(9.5+/-1.2)x10^22^cm^-2^, number density n(H_2_)=(2.9+/-0.4)x10^5^cm^-3^, and mass M_core_=1.0+/-0.3M_{sun}_ compared to the cores in the Orion A [R=0.11pc, N(H_2_)=(2.3+/-0.3)x10^23^cm^-2^, n(H_2_)=(3.8+/-0.5)x10^5^cm^-3^, and M_core_=2.4+/-0.3M_{sun}_] and Orion B [R=0.16pc, N(H_2_)=(3.8+/-0.4)x10^23^cm^-2^, n(H_2_)=(15.6+/-1.8)x10^5^cm^-3^, and M_core_=2.7+/-0.3M_{sun}_] clouds. These core properties in the {lambda} Orionis cloud can be attributed to the photodissociation and external heating by the nearby H II region, which may prevent the PGCCs from forming gravitationally bound structures and eventually disperse them. These results support the idea of negative stellar feedback on core formation.
- ID:
- ivo://CDS.VizieR/J/MNRAS/416/2
- Title:
- Photodissociation regions in M33
- Short Name:
- J/MNRAS/416/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive total (atomic + molecular) hydrogen densities in giant molecular clouds (GMCs) in the nearby spiral galaxy M33 using a method that views the atomic hydrogen near regions of recent star formation as the product of photodissociation. Far-ultraviolet (FUV) photons emanating from a nearby OB association produce a layer of atomic hydrogen on the surfaces of nearby GMCs. Our approach provides an estimate of the total hydrogen density in these GMCs from observations of the excess FUV emission that reaches the GMC from the OB association and of the excess 21-cm radio HI emission produced after these FUV photons convert H2 into HI on the GMC surface. The method provides an alternative approach to the use of CO emission as a tracer of H2 in GMCs and is especially sensitive to a range of densities well below the critical density for CO(1-0) emission.
