- ID:
- ivo://CDS.VizieR/J/A+A/587/A118
- Title:
- N2H+, N2D+ and C17O spectra in Ophiuchus
- Short Name:
- J/A+A/587/A118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In cold (T<25K) and dense (n_H_>10^4^cm^-3^) interstellar clouds, molecules such as CO are significantly frozen onto dust grain surfaces. Deuterium fractionation is known to be very efficient in these conditions as CO limits the abundance of H_3_^+^, which is the starting point of deuterium chemistry. In particular, N_2_D^+^ is an excellent tracer of dense and cold gas in star- forming regions. We measure the deuterium fraction, RD, and the CO depletion factor, fd, towards a number of starless and protostellar cores in the L1688 region of the Ophiuchus molecular cloud and search for variations based upon environmental differences across L1688. The kinematic properties of the dense gas traced by the N_2_H^+^ and N_2_D^+^ (1-0) lines are also discussed. Deuterium fraction has been measured via observations of the J=1-0 transition of N2H+ and N2D+ towards 33 dense cores in different regions of L1688. We estimated the CO depletion factor using C^17^O(1-0) and 850 micron dust continuum emission from the SCUBA survey. We carried out all line observations with the IRAM 30 meter antenna.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/527/A41
- Title:
- NH3 observations in outflows
- Short Name:
- J/A+A/527/A41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the observations of the (J,K)=(1,1) and the (J,K)=(2,2) inversion transitions of the NH3 molecule towards a large sample of 40 regions with molecular or optical outflows, using the 37m radio telescope of the Haystack Observatory. We detected NH3 emission in 27 of the observed regions and we mapped this emission in 25 of them. Additionally, we searched for the 6_16-5_23 H2O maser line towards six regions, detecting H2O maser emission in two of them. We estimate the physical parameters of the regions mapped in NH3 and, for each particular region, we analyze the distribution of high density gas and its relationship with the presence of young stellar objects We confirm with a larger sample of regions that the NH3 line emission is more intense towards molecular outflow sources than towards sources with optical outflow, suggesting a possible evolutionary scheme in which young stellar objects associated with molecular outflows lose progressively their neighboring high-density gas, weakening both the NH3 emission and the molecular outflow in the process, and making optical jets more easily detectable as the total amount of gas decreases.
- ID:
- ivo://CDS.VizieR/J/A+A/599/A135
- Title:
- NH_3_ Odin observations towards Sgr A
- Short Name:
- J/A+A/599/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Odin satellite is now into its sixteenth year of operation, much surpassing its design life of two years. One of the sources which Odin has observed in great detail is the Sgr A Complex in the centre of the Milky Way. The aim is to study the presence of NH_3_ in the Galactic Centre and spiral arms. Recently, Odin has made complementary observations of the 572GHz NH_3_ line towards the Sgr A +50km/s cloud and Circumnuclear Disk (CND). Significant NH_3_ emission has been observed in both the +50km/s cloud and the CND. Clear NH_3_ absorption has also been detected in many of the spiral arm features along the line of sight from the Sun to the core of our Galaxy. The very large velocity width (80km/s) of the NH_3_ emission associated with the shock region in the southwestern part of the CND may suggest a formation/desorption scenario similar to that of gas-phase H_2_O in shocks/outflows.
- ID:
- ivo://CDS.VizieR/J/ApJ/739/100
- Title:
- [NII] observations of the Carina Nebula (NGC 3372)
- Short Name:
- J/ApJ/739/100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a ~250arcmin^2^ mapping of the 205um [NII] fine-structure emission over the northern Carina Nebula, including the Car I and Car II HII regions. Spectra were obtained using the South Pole Imaging Fabry-Perot Interferometer (SPIFI) at the Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) at the South Pole. We supplement the 205um data with new reductions of far-IR fine-structure spectra from the Infrared Space Observatory (ISO) Long Wavelength Spectrometer (LWS) in 63um [OI], 122um [NII], 146um [OI], and 158um [CII]; the 146um [OI] data include 90 raster positions which have not been previously published. Morphological comparisons are made with optical, radio continuum, and CO maps. The 122/205 line ratio is used to probe the density of the low-ionization gas, and the 158/205 line ratio is used to probe the fraction of C^+^ arising from photodissociation regions (PDRs). The [OI] and [CII] lines are used to construct a PDR model of Carina. When the PDR properties are compared with other sources, Carina is found to be more akin to 30 Doradus than galactic star-forming regions such as Orion, M17, or W49; this is consistent with the view of Carina as a more evolved region, where much of the parent molecular cloud has been ionized or swept away. These data constitute the first ground-based detection of the 205um [NII] line, and the third detection overall since those of COBE FIRAS and the Kuiper Airborne Observatory in the early 1990s.
- ID:
- ivo://CDS.VizieR/J/A+A/615/A18
- Title:
- NIKA view of two star-forming IRDCs
- Short Name:
- J/A+A/615/A18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The thermal emission of dust grains is a powerful tool for probing cold, dense regions of molecular gas in the interstellar medium, and so constraining dust properties is key to obtaining accurate measurements of dust mass and temperature. By placing constraints on the dust emissivity spectral index, {beta}, towards two star-forming infrared dark clouds - SDC18.888-0.476 and SDC24.489-0.689 - we aim to evaluate the role of mass concentration in the associated star-formation activity. We exploited the simultaneous 1.2mm and 2.0mm imaging capability of the NIKA camera on the IRAM 30m telescope to construct maps of {beta} for both clouds, and by incorporating Herschel observations, we created H_2_ column density maps with 13" angular resolution. While we find no significant systematic radial variations around the most massive clumps in either cloud on 0.1 pc scales, their mean {beta} values are significantly different, with {bar}{beta}=2.07+/-0.09(random)+/-0.25(systematic) for SDC18.888-0.476 and {bar}{beta}=1.71+/-0.09(random)+/-0.25(systematic) for SDC24.489-0.689. These differences could be a consequence of the very different environments in which both clouds lie, and we suggest that the proximity of SDC18.888-0.476 to the W39 HII region may raise {beta} on scales of ~1pc. We also find that the mass in SDC24.489-0.689 is more centrally concentrated and circularly symmetric than in SDC18.888-0.476, and is consistent with a scenario in which spherical globally-collapsing clouds concentrate a higher fraction of their mass into a single core than elongated clouds that will more easily fragment, distributing their mass into many cores. We demonstrate that {beta} variations towards interstellar clouds can be robustly constrained with high signal-to-noise ratio (S/N) NIKA observations, providing more accurate estimates of their masses. The methods presented here will be applied to the Galactic Star Formation with NIKA2 (GASTON) guaranteed time large programme, extending our analysis to a statistically significant sample of star-forming clouds.
- ID:
- ivo://CDS.VizieR/J/MNRAS/478/3693
- Title:
- N in Galactic high-mass star-forming cores
- Short Name:
- J/MNRAS/478/3693
- Date:
- 10 Dec 2021 00:14:43
- Publisher:
- CDS
- Description:
- The fractionation of nitrogen (N) in star-forming regions is a poorly understood process. To put more stringent observational constraints on the N-fractionation, we have observed with the IRAM-30-m telescope a large sample of 66 cores in massive star-forming regions. We targeted the (1-0) rotational transition of HN^13^C, HC^15^N, H^13^CN and HC^15^N, and derived the ^14^N/^15^N ratio for both HCN and HNC. We have completed this sample with that already observed by Colzi et al., and thus analysed a total sample of 87 sources. The ^14^N/^15^N ratios are distributed around the Proto-Solar Nebula value with a lower limit near the TA value (~272). We have also derived the ^14^N/^15^N ratio as a function of the Galactocentric distance and deduced a linear trend based on unprecedented statistics. The Galactocentric dependences that we have found are consistent, in the slope, with past works but we have found a new local ^14^N/^15^N value of ~400, i.e. closer to the Prosolar Nebula value. A second analysis was done, and a parabolic Galactocentric trend was found. Comparison with Galactic chemical evolution models shows that the slope until 8 kpc is consistent with the linear analysis, while the flattening trend above 8 kpc is well reproduced by the parabolic analysis.
- ID:
- ivo://CDS.VizieR/J/A+A/523/A16
- Title:
- NIR imaging of HH 223
- Short Name:
- J/A+A/523/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The dark cloud Lynds 723 (L723) is a low-mass star-forming region where one of the few known cases of a quadrupolar CO outflow has been reported. Two recent works have found that the radio continuum source VLA 2, towards the centre of the CO outflow, is actually a multiple system of young stellar objects (YSOs). We imaged a field of 5'x 5' centred on HH 223, which includes the whole region of the quadrupolar CO outflow with narrow-band filters centred on the [FeII] 1.644mum and H_2_ 2.122mum lines, together with off-line H_c_ and K_c_ filters. Our aim is to study L723 in the near-infrared and look for line-emission nebulae associated with the optical and CO outflows.
- ID:
- ivo://CDS.VizieR/J/ApJ/837/118
- Title:
- NIR knots in the Cas A supernova remnant
- Short Name:
- J/ApJ/837/118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of broadband (0.95-2.46{mu}m) near-infrared spectroscopic observations of the Cassiopeia A supernova remnant. Using a clump-finding algorithm in two-dimensional dispersed images, we identify 63 "knots" from eight slit positions and derive their spectroscopic properties. All of the knots emit [FeII] lines together with other ionic forbidden lines of heavy elements, and some of them also emit H and He lines. We identify 46 emission line features in total from the 63 knots and measure their fluxes and radial velocities. The results of our analyses of the emission line features based on principal component analysis show that the knots can be classified into three groups: (1) He-rich, (2) S-rich, and (3) Fe-rich knots. The He-rich knots have relatively small, <~200km/s, line-of-sight speeds and radiate strong He I and [FeII] lines resembling closely optical quasi-stationary flocculi of circumstellar medium, while the S-rich knots show strong lines from O-burning material with large radial velocities up to ~2000km/s indicating that they are supernova ejecta material known as fast-moving knots. The Fe-rich knots also have large radial velocities but show no lines from O-burning material. We discuss the origin of the Fe-rich knots and conclude that they are most likely "pure" Fe ejecta synthesized in the innermost region during the supernova explosion. The comparison of [FeII] images with other waveband images shows that these dense Fe ejecta are mainly distributed along the southwestern shell just outside the unshocked ^44^Ti in the interior, supporting the presence of unshocked Fe associated with ^44^Ti.
- ID:
- ivo://CDS.VizieR/J/A+A/647/A109
- Title:
- NIR observations of LDN1512
- Short Name:
- J/A+A/647/A109
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Light scattering at near-infrared wavelengths has been used to study the optical properties of the interstellar dust grains, but these studies are limited by the assumptions on the strength of the radiation field. On the other hand, thermal dust emission can be used to constrain the properties of the radiation field, although this is hampered by uncertainty about the dust emissivity. Combining light scattering and emission studies allows us to probe the properties of the dust grains in detail. We wish to study if current dust models allow us to model a molecular cloud simultaneously in the near infrared (NIR) and far infrared (FIR) wavelengths and compare the results with observations. Our aim is to place constraints on the properties of the dust grains and the strength of the radiation field. We present computations of dust emission and scattered light of a quiescent molecular cloud LDN1512. We use NIR observations covering the J, H, and Ks bands, and FIR observations between 250 and 500 micron from Herschel space telescope. We construct radiative transfer models for LDN1512 that include an anisotropic radiation field and a three-dimensional cloud model. We are able to reproduce the observed FIR observations, with a radiation field derived from the DIRBE observations, with all of the tested dust models. However, with the same density distribution and the assumed radiation field, the models fail to reproduce the observed NIR scattering in all cases except for models that take into account dust evolution via coagulation and mantle formation. The intensity from the diffuse interstellar medium (ISM) like, dust models can be increased to match the observed one by reducing the derived density, increasing the intensity of the background sky and the strength of the radiation field between factors from 2 to 3. We find that the column densities derived from our radiative transfer modelling can differ by a factor of up to two, compared to the column densities derived from the observations with modified blackbody fits. The discrepancy in the column densities is likely caused because of temperature difference between a modified blackbody fit and the real spectra.The difference between the fitted temperature and the true temperature could be as high as {Delta}T=+/-1.5K. We show that the observed dust emission can be reproduced with several different assumptions about the properties of the dust grains. However, in order to reproduce the observed scattered surface brightness dust evolution must be taken into account.
- ID:
- ivo://CDS.VizieR/J/ApJ/741/35
- Title:
- NIR photometry and polarization in NGC 2264
- Short Name:
- J/ApJ/741/35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Near-infrared imaging polarimetry in the J, H, and Ks bands has been carried out for the protostellar cluster region around NGC 2264 IRS 2 in the Monoceros OB1 molecular cloud. Various infrared reflection nebula clusters (IRNCs) associated with NGC 2264 IRS 2 and the IRAS 12 S1 core, as well as local infrared reflection nebulae (IRNe), were detected. The illuminating sources of the IRNe were identified with known or new near- and mid-infrared sources. In addition, 314 point-like sources were detected in all three bands and their aperture polarimetry was studied. Using a color-color diagram, reddened field stars and diskless pre-main-sequence stars were selected to trace the magnetic field (MF) structure of the molecular cloud. The mean polarization position angle of the point-like sources is 81+/-29{deg} in the cluster core, and 58+/-24{deg} in the perimeter of the cluster core, which is interpreted as the projected direction on the sky of the MF in the observed region of the cloud. The Chandrasekhar-Fermi method gives a rough estimate of the MF strength to be about 100uG. A comparison with recent numerical simulations of the cluster formation implies that the cloud dynamics is controlled by the relatively strong MF. The local MF direction is well associated with that of CO outflow for IRAS 12 S1 and consistent with that inferred from submillimeter polarimetry. In contrast, the local MF direction runs roughly perpendicular to the Galactic MF direction.