Water in star-forming regions with Herschel: highly excited molecular emission from the NGC 1333 IRAS 4B outflow
Gregory J. Herczeg, Agata Karska, Simon Bruderer, Lars E. Kristensen, Ewine F. van Dishoeck, Jes K. Jørgensen, Ruud Visser, Susanne F. Wampfler, Edwin A. Bergin… 展开作者
Gregory J. Herczeg, Agata Karska, Simon Bruderer, Lars E. Kristensen, Ewine F. van Dishoeck, Jes K. Jørgensen, Ruud Visser, Susanne F. Wampfler, Edwin A. Bergin, Umut A. Yildiz, Klaus M. Pontoppidan, Javier Gracia-Carpio
During the embedded phase of pre-main sequence stellar evolution, a disk forms from the dense envelope while an accretion-driven outflow carves out a cavity within the envelope. Highly excited H2O emission in spatially unresolved Spitzer/IRS spectra of a low-mass Class 0 object, NGC 1333 IRAS 4B, has previously been attributed to the envelope-disk accretion shock but could instead be produced in an outflow. As part of the survey of low-mass sources in the Water in Star Forming Regions with Herschel (WISH-LM) program, we used Herschel/PACS to obtain a far-IR spectrum and several Nyquist-sampled spectral images with to determine the origin of excited H2O emission from NGC 1333 IRAS 4B. The spectrum has high signal-to-noise in a rich forest of H2O, CO, and OH lines, providing a near-complete census of far-IR molecular emission from a Class 0 protostar. The excitation diagrams for the three molecules all require fits with two excitation temperatures, indicating the presence of two physical components. The highly excited component of H2O emission is characterized by subthermal excitation of 1500 K gas with a density of 10^5 - 10^7 cm-3, conditions that also reproduce the mid-IR H2O emission detected by Spitzer. On the other hand, a high density, low temperature gas can reproduce the H2O spectrum observed by Spitzer but underpredicts the H2O lines seen by Herschel. Nyquist-sampled spectral maps of several lines show two spatial components of H2O emission, one centered at 1200 AU south of the central source at the position of the blueshifted outflow lobe and a second centered on-source. Both spatial components of the far-IR H2O emission are consistent with emission from the outflow. The gas cooling from the IRAS 4B envelope cavity walls is dominated by far-IR H2O emission, in contrast to stronger [O I] and CO cooling from more evolved protostars. [one sentence truncated]
We performed Herschel observations of the continuum and line emission from the high-mass star-forming region IRAS20126+4104, which hosts a well-studied B-type (proto)star powering a bipolar outflow and is associated with a Keplerian circumstellar disk. The continuum images at six wavelengths allowed us to derive an accurate estimate of the bolometric luminosity and mass of the molecular clump enshrouding the disk. The same region has been mapped in 12 rotational transitions of carbon monoxide, which were used in synergy with the continuum data to determine the temperature and density distribut…
We discuss a new IRAS Faint Source Catalog galaxy redshift catalogue (RIFSCz) which incorporates data from Galex, SDSS, 2MASS, WISE, Akari and Planck. Akari fluxes are consistent with photometry from other far infrared and submillimetre missions provided an aperture correction is applied. Results from the Hermes-SWIRE survey in Lockman are also discussed briefly, and the strong contrast between the galaxy populations selected at 60 and 500 mu is summarized.
To understand the origin of the diversity observed in exoplanetary systems, it is crucial to characterize the early stages of their formation, represented by Solar-type protostars. Likely, the gaseous chemical content of these objects directly depends on the composition of the dust grain mantles formed before the collapse. Directly retrieving the ice mantle composition is challenging, but it can be done indirectly by observing the major components, such as NH3 and CH3OH at cm wavelengths, once they are released into the gas-phase during the warm protostellar stage. We observed several CH3OH an…
We report high angular resolution observations of linearly polarized dust emission towards the Class 0 young stellar object (YSO) NGC1333 IRAS4A (hereafter, IRAS4A) using the Karl G. Jansky Very Large Array (JVLA) at K (11.5-16.7 mm), Ka (8.1-10.3 mm), and Q bands (6.3-7.9 mm), and using the Atacama Large Millimeter Array (ALMA) at Band 6 (1.2 mm) and Band 7 (0.85-0.89 mm). On 100-1000 AU scales, all of these observations consistently trace the hourglass shaped magnetic field topology as shown in the previous studies. In the innermost 100 AU region of IRAS4A1, the polarization position angles …
We have analyzed the ALMA archival data of the SO ($J_N=6_5-5_4$ and $J_N=7_6-6_5$), CO ($J=2-1$), and CCH ($N=3-2, J=7/2-5/2, F=4-3$) lines from the class 0 protobinary system, NGC1333 IRAS 4A. The images of SO ($J_N = 6_5-5_4$) and CO ($J=2-1$) successfully separate two northern outflow lobes connected to each protostar, IRAS 4A1 and IRAS 4A2. The outflow from IRAS 4A2 shows an S-shaped morphology, consisting of a flattened envelope around IRAS 4A2 with two outflow lobes connected to both edges of the envelope. The flattened envelope surrounding IRAS 4A2 has an opposite velocity gradient to …
The NGC 1333 IRAS 4B region was observed in the 6.9 mm and 1.3 cm continuum with an angular resolution of about 0.4 arcseconds. IRAS 4BI was detected in both bands, and BII was detected in the 6.9 mm continuum only. The 1.3 cm source of BI seems to be a disk-like flattened structure with a size of about 50 AU. IRAS 4BI does not show any sign of multiplicity. Examinations of archival infrared images show that the dominating emission feature in this region is a bright peak in the southern outflow driven by BI, corresponding to the molecular hydrogen emission source HL 9a. Both BI and BII are und…
We present an analysis of the IRAS 08589-4714 star-forming region. This region harbors candidate young stellar objects identified in the WISE and Herschel images using color index criteria and spectral energy distributions (SEDs). The SEDs of some of the infrared sources and the 70 microns radial intensity profile of the brightest source (IRS 1) are modeled from Herschel fluxes using the one-dimensional radiative transfer DUSTY code. For these objects, we estimate the envelope masses, sizes, densities, and luminosities which suggest that they are very young, massive and luminous objects at ear…
IRAS 20319+3958 in Cygnus X South is a rare example of a free-floating globule (mass ~240 Msun, length ~1.5 pc) with an internal HII region created by the stellar feedback of embedded intermediate-mass stars, in particular, one Herbig Be star. Here, we present a Herschel/HIFI CII 158 mu map of the whole globule and a large set of other FIR lines (mid-to high-J CO lines observed with Herschel/PACS and SPIRE, the OI 63 mu line and the CO 16-15 line observed with upGREAT on SOFIA), covering the globule head and partly a position in the tail. The CII map revealed that the whole globule is probably…
The NGC 1333 IRAS 4A protobinary was observed in the ammonia (2, 2) and (3, 3) lines with an angular resolution of 0.3 arcsec. The ammonia emission source of IRAS 4A2 is elongated in the direction perpendicular to the bipolar jet and has a size of 0.55 arcsec or 130 AU. This emission structure was interpreted as a circumstellar disk around the IRAS 4A2 protostar, and the rotation kinematics of the disk was investigated by making a position-velocity diagram along the major axis. Assuming a Keplerian rotation, the disk has a rotation velocity of 1.8 km/s at a radius of 20 AU, which implies a cen…
Aims. The aim of this paper is to study deuterated water in the solar-type protostars NGC1333 IRAS4A and IRAS4B, to compare their HDO abundance distribution with other star-forming regions, and to constrain their HDO/H2O ratios. Methods. Using the Herschel/HIFI instrument as well as ground-based telescopes, we observed several HDO lines covering a large excitation range (Eup/k=22-168 K) towards these protostars and an outflow position. Non-LTE radiative transfer codes were then used to determine the HDO abundance profiles in these sources. Results. The HDO fundamental line profiles show a very…
There is evidence that the star formation process is linked to the intricate net of filaments in molecular clouds, which may be also due to gas compression from external triggers. We studied the southern region of the Perseus NGC 1333 molecular cloud, known to be heavily shaped by similar external triggers, to shed light on the process that perturbed the filament where the Class 0 IRAS4 protostars lie. We use new IRAM-NOEMA observations of SiO and CH3OH, both known to trace violent events as shocks, toward IRAS 4A as part of the Large Program Seeds Of Life in Space (SOLIS). We detected three p…
In molecular outflows from forming low-mass protostars, most oxygen is expected to be locked up in water. However, Herschel observations have shown that typically an order of magnitude or more of the oxygen is still unaccounted for. To test if the oxygen is instead in atomic form, SOFIA-GREAT observed the R1 position of the bright molecular outflow from NGC1333-IRAS4A. The [OI] 63 um line is detected and spectrally resolved. From an intensity peak at +15 km/s, the intensity decreases until +50 km/s. The profile is similar to that of high-velocity (HV) H2O and CO 16-15, the latter observed simu…
We present Submillimeter Array (SMA) polarization observations of the CO $J$ = 3--2 line toward the NGC1333 IRAS 4A. The CO Stokes $I$ maps at an angular resolution of $\sim$1$\arcsec$ reveal two bipolar outflows from the binary sources of the NGC 1333 IRAS 4A. The kinematic features of the CO emission can be modeled by wind-driven outflows at $\sim$ 20$\arcdeg$ inclined from the plane of the sky. Close to the protostars the CO polarization, at an angular resolution of $\sim$$2\farcs3$, has a position angle approximately parallel to the magnetic field direction inferred from the dust polarizat…
We report molecular line observations of the NGC 1333 IRAS 4C outflow in the Perseus Molecular Cloud with the Atacama Large Millimeter/Submillimeter Array. The CCH and CS emission reveal an outflow cavity structure with clear signatures of rotation with respect to the outflow axis. The rotation is detected from about 120 au up to about 1400 au above the envelope/disk mid-plane. As the distance to the central source increases, the rotation velocity of the outflow decreases while the outflow radius increases, which gives a flat specific angular momentum distribution along the outflow. The mean s…
Aims: A unique environment to study how interstellar Complex Organic Molecules (iCOMs) can be formed is the shocked gas along low-mass protostellar outflows, as the dust mantles composition is sputtered into the gas phase. The chemical richness in these environments has been so far studied only in the L1157 blue shifted outflow. Methods: To understand if the L1157-B1 case is unique, we imaged the NGC 1333 IRAS 4A outflows using the NOEMA (NOrthern Extended Millimeter Array) interferometer as part of the IRAM SOLIS (Seeds Of Life in Space) Large Program and compared the observations with the GR…
We present the first overview of the Herschel observations of the nearby high-mass star-forming region NGC 7538, taken as part of the Herschel imaging study of OB Young Stellar objects (HOBYS) Key Programme. These PACS and SPIRE maps cover an approximate area of one square degree at five submillimeter and far-infrared wavebands. We have identified 780 dense sources and classified 224 of those. With the intention of investigating the existence of cold massive starless or class 0-like clumps that would have the potential to form intermediate- to high-mass stars, we further isolate 13 clumps as t…
We present Herschel images from the HOBYS key program of the Eagle Nebula (M16) in the far-infrared and sub-millimetre, using the PACS and SPIRE cameras at 70μm, 160μm, 250μm, 350μm, 500μm. M16, home to the Pillars of Creation, is largely under the influence of the nearby NGC6611 high-mass star cluster. The Herschel images reveal a clear dust temperature gradient running away from the centre of the cavity carved by the OB cluster. We investigate the heating effect of NGC6611 on the entire M16 star-forming complex seen by Herschel including the diffuse cloud environment and the dense filamentar…
The bipolar jet of the NGC 1333 IRAS 4A2 protostar shows a velocity gradient in the direction perpendicular to the jet axis. This lateral velocity gradient can be seen throughout the jet imaged in a silicon monoxide line, 2500-8700 AU from the driving source, and is consistent with the rotation of the accretion disk. If this gradient is caused by the rotation of the jet around its axis, the average specific angular momentum is about 1.5 x 10^21 cm^2 s^-1. Comparison of the kinematics between the jet and the disk suggests that the jet-launching region on the disk has a radius of about 2 AU, whi…
There is significant scientific value to be gained from combining AKARI fluxes with data at other far-IR wavelengths from the IRAS and Herschel missions. To be able to do this we must ensure that there are no systematic differences between the datasets that need to be corrected before the fluxes are compatible with each other. One such systematic effect identified in the BSCv1 data is the issue of beam corrections. We determine these for the BSCv2 data by correlating ratios of appropriate IRAS and AKARI bands with the difference in 2MASS J band extended and point source magnitudes for sources …
We performed J- and R-band linear polarimetry with the 4.2 m William Herschel Telescope at the Observatorio del Roque de los Muchachos and with the 1.6 m telescope at the Observatório do Pico dos Dias, respectively, to derive the magnetic field geometry of the diffuse molecular cloud surrounding the embedded protostellar system NGC 1333 IRAS 4A. We obtained interstellar polarization data for about two dozen stars. The distribution of polarization position angles has low dispersion and suggests the existence of an ordered magnetic field component at physical scales larger than the protostar. So…
The ESA Herschel Spectral and Photometric Imaging Receiver (SPIRE) Fourier Transform Spectrometer (FTS) Spectral Feature Finder (FF) project is an automated spectral feature fitting routine developed within the SPIRE instrument team to extract all prominent spectral features from all publicly available SPIRE FTS observations. In this work, we demonstrate the use of the FF information extracted from three observations of the edge-on spiral galaxy NGC 891 to measure the rotation of NII and CI gas at Far-infrared frequencies in complement to radio observations of the HI 21cm line and the CO(1-0) …
Galaxy evolution scenarios predict that the feedback of star formation and nuclear activity (AGN) can drive the transformation of gas-rich spiral mergers into ULIRGs, and, eventually, lead to the build-up of QSO/elliptical hosts. We study the role that star formation and AGN feedback have in launching and maintaining the molecular outflows in two starburst-dominated advanced mergers, NGC1614 and IRAS17208-0014, by analyzing the distribution and kinematics of their molecular gas reservoirs. We have used the PdBI array to image with high spatial resolution (0.5"-1.2") the CO(1-0) and CO(2-1) lin…
Photodissociation regions (PDRs) contain a large fraction of all of the interstellar matter in galaxies. Classical examples include the boundaries between ionized regions and molecular clouds in regions of massive star formation, marking the point where all of the photons energetic enough to ionize hydrogen have been absorbed. In this paper we determine the physical properties of the PDRs associated with the star forming regions IRAS 23133+6050 and S 106 and present them in the context of other Galactic PDRs associated with massive star forming regions. We employ Herschel PACS and SPIRE spectr…
It is not well known what drives the chemistry of a protostellar envelope, in particular the role of the stellar mass and the outflows on its chemical enrichment. We study the chemical structure of NGC 1333 IRAS 4A in order to (i) investigate the influence of the outflows on the chemistry, (ii) constrain the age of our object, (iii) compare it with a typical high-mass protostellar envelope. In our analysis we use JCMT line mapping and HIFI pointed spectra. To study the influence of the outflow on the degree of deuteration, we compare JCMT maps of HCO+ and DCO+ with non-LTE (RADEX) models in a …
The mass segregation of stellar clusters could be primordial rather than dynamical. Despite the abundance of studies of mass segregation for stellar clusters, those for stellar progenitors are still scarce, so the question on the origin and evolution of mass segregation is still open. Our goal is to characterize the structure of the NGC 2264 molecular cloud and compare the populations of clumps and young stellar objects (YSOs) in this region whose rich YSO population has shown evidence of sequential star formation. We separated the Herschel column density map of NGC 2264 in three subregions an…
Aims: In this paper we focus on the occurrence of glycolaldehyde (HCOCH2OH) in young solar analogs by performing the first homogeneous and unbiased study of this molecule in the Class 0 protostars of the nearby Perseus star forming region. Methods: We obtained sub-arcsec angular resolution maps at 1.3mm and 1.4mm of glycolaldehyde emission lines using the IRAM Plateau de Bure (PdB) interferometer in the framework of the CALYPSO IRAM large program. Results: Glycolaldehyde has been detected towards 3 Class 0 and 1 Class I protostars out of the 13 continuum sources targeted in Perseus: NGC1333-IR…
We present the results of unbiased 22 GHz H2O water and 44 GHz class I CH3OH methanol maser surveys in the central 7x10 arcmin area of NGC 1333 and two additional mapping observations of a 22 GHz water maser in a ~3x3arcmin area of the IRAS4A region. In the 22 GHz water maser survey of NGC 1333 with sensitivity of sigma~0.3Jy, we confirmed masers toward H2O(B) in the region of HH 7-11 and IRAS4B. We also detected new water masers at ~20arcsec away in the western direction of IRAS4B or ~25arcsec away in the southern direction of IRAS4A. We could not however find young stellar objects or molecul…
Observations of dust polarized emission toward star forming regions trace the magnetic field component in the plane of the sky and provide constraints to theoretical models of cloud collapse. We compare high-angular resolution observations of the submillimeter polarized emission of the low-mass protostellar source NGC 1333 IRAS 4A with the predictions of three different models of collapse of magnetized molecular cloud cores. We compute the Stokes parameters for the dust emission for the three models. We then convolve the results with the instrumental response of the Submillimeter Array observa…
We investigate the origin of complex organic molecules (COMs) in the gas phase around the low-mass Class~0 protostar NGC1333-IRAS2A, to determine if the COM emission lines trace an embedded disk, shocks from the protostellar jet, or the warm inner parts of the protostellar envelope. In the framework of the CALYPSO (Continuum And Lines in Young ProtoStellar Objects) IRAM Plateau de Bure survey, we obtained large bandwidth spectra at sub-arcsecond resolution towards NGC 1333-IRAS2A. We identify the emission lines towards the central protostar and perform Gaussian fits to constrain the size of th…
We present Herschel/HIFI observations (WISH KP) of 14 water lines in a small sample of galactic massive protostellar objects: NGC6334I(N), DR21(OH), IRAS16272-4837, and IRAS05358+3543. We analyze the gas dynamics from the line profiles. Through modeling of the observations using RATRAN, we estimate outflow, infall, turbulent velocities, molecular abundances, and investigate any correlation with the evolutionary status of each source. The molecular line profiles exhibit a broad component coming from the shocks along the cavity walls associated with the protostars, and an infalling (or expansion…
We report ALMA observations of NGC 1333 IRAS 4A, a young low-mass protostellar binary, referred as 4A1 and 4A2. With multiple H$_2$CO transitions and HNC (4$-$3) observed at a resolution of 0.25" ($\sim$70 au), we investigate the gas kinematics of 4A1 and 4A2. Our results show that, on the large angular scale ($\sim$10"), 4A1 and 4A2 each display a well-collimated outflow along the N-S direction, and an S-shaped morphology is discerned in the outflow powered by 4A2. On the small scale ($\sim$0.3"), 4A1 and 4A2 exhibit distinct spectral features toward the continuum centroid, with 4A1 showing s…
Dust polarization in millimeter (and centimeter) has been mapped in disks around an increasing number of young stellar objects. It is usually thought to come from emission by magnetically aligned (non-spherical) grains, but can also be produced by dust scattering. We present a semi-analytic theory of disk polarization that includes both the direction emission and scattering, with an emphasis on their relative importance and how they are affected by the disk inclination. For face-on disks, both emission and scattering tend to produce polarization in the radial direction, making them difficult t…
The determination of the physical conditions in molecular clouds is a key step towards our understanding of their formation and evolution of associated star formation. We investigate the density, temperature, and column density of both dust and gas in the photodissociation regions (PDRs) located at the interface between the atomic and cold molecular gas of the NGC 7023 reflection nebula. We study how young stars affect the gas and dust in their environment. Our approach combining both dust and gas delivers strong constraints on the physical conditions of the PDRs. We find dense and warm molecu…
To constrain models of high-mass star formation, the Herschel/HOBYS KP aims at discovering massive dense cores (MDCs) able to host the high-mass analogs of low-mass prestellar cores, which have been searched for over the past decade. We here focus on NGC6334, one of the best-studied HOBYS molecular cloud complexes. We used Herschel PACS and SPIRE 70-500mu images of the NGC6334 complex complemented with (sub)millimeter and mid-infrared data. We built a complete procedure to extract ~0.1 pc dense cores with the getsources software, which simultaneously measures their far-infrared to millimeter f…
Large spatial-spectral surveys are more and more common in astronomy. This calls for the need of new methods to analyze such mega- to giga-pixel data-cubes. In this paper we present a method to decompose such observations into a limited and comprehensive set of components. The original data can then be interpreted in terms of linear combinations of these components. The method uses non-negative matrix factorization (NMF) to extract latent spectral end-members in the data. The number of needed end-members is estimated based on the level of noise in the data. A Monte-Carlo scheme is adopted to e…
The NGC 1333 IRAS 4A protobinary was observed in the 1.3 cm and 6.9 mm continuum and the ammonia and SiO lines, with an angular resolution of about 0.4 arcseconds. The continuum maps show the circumstellar structures of the two protostars, A1 and A2. The A1 system is brighter and more massive than the A2 system. The ratio of mass, including dense gas and protostar, is about 6. The properties of the circumstellar disks and outflows suggest that A1 may be younger than A2. The deflected part of the northeastern jet of A2 is bright in the SiO line, and the distance between the brightest peak and d…
The total infra-red (IR) luminosity (L_IR) can be used as a robust measure of a galaxy's star formation rate (SFR), even in the presence of an active galactic nucleus (AGN), or when optical emission lines are weak. Unfortunately, existing all sky far-IR surveys, such as the Infra-red Astronomical Satellite (IRAS) and AKARI, are relatively shallow and are biased towards the highest SFR galaxies and lowest redshifts. More sensitive surveys with the Herschel Space Observatory are limited to much smaller areas. In order to construct a large sample of L_IR measurements for galaxies in the nearby un…
We present Herschel dust continuum, James Clerk Maxwell Telescope CO(3-2) observations and a search for [CII] 158 micron and [OI] 63 micron spectral line emission for the brightest early-type dwarf satellite of Andromeda, NGC 205. While direct gas measurements (Mgas ~ 1.5e+6 Msun, HI + CO(1-0)) have proven to be inconsistent with theoretical predictions of the current gas reservoir in NGC 205 (> 1e+7 Msun), we revise the missing interstellar medium mass problem based on new gas mass estimates (CO(3-2), [CII], [OI]) and indirect measurements of the interstellar medium content through dust conti…
We present deep far-infrared observations of the nearby edge-on galaxy NGC 891 obtained with the Herschel Space Observatory and the Spitzer Space Telescope. The maps confirm the detection of thermal emission from the inner circumgalactic medium (halo) and spatially resolve a dusty superbubble and a dust spur (filament). The dust temperature of the halo component is lower than that of the disk but increases across a region of diameter ~8.0 kpc extending at least 7.7 kpc vertically from one side of the disk, a region we call a superbubble because of its association with thermal X-ray emission an…
A multi-wavelength investigation of the star forming complex IRAS 20286+4105, located in the Cygnus-X region, is presented here. Near-infrared K-band data is used to revisit the cluster / stellar group identified in previous studies. The radio continuum observations, at 610 and 1280 MHz show the presence of a HII region possibly powered by a star of spectral type B0 - B0.5. The cometary morphology of the ionized region is explained by invoking the bow-shock model where the likely association with a nearby supernova remnant is also explored. A compact radio knot with non-thermal spectral index …
Large scale spectral maps of star forming regions enable the comparative study of the gas excitation around an ensemble of sources at a common frame of reference, providing direct insights in the multitude of processes involved. In this paper we employ spectral-line maps to decipher the excitation, the kinematical and dynamical processes in NGC 1333 as revealed by a number of different emission lines, aiming to set a reference for the applicability of tracers in constraining diverse physical processes. We reconstruct line maps for H$_2$ , CO, H$_2$O and C$^+$ using data obtained with the Spitz…
NGC 1333 IRAS 4A and IRAS 4B sources are among the best studied Stage 0 low-mass protostars which are driving prominent bipolar outflows. Most studies have so far concentrated on the colder parts (T<30K) of these regions. The aim is to characterize the warmer parts of the protostellar envelope in order to quantify the feedback of the protostars on their surroundings in terms of shocks, UV heating, photodissociation and outflow dispersal. Fully sampled large scale maps of the region were obtained; APEX-CHAMP+ was used for 12CO 6-5, 13CO 6-5 and [CI] 2-1, and JCMT-HARP-B for 12CO 3-2 emissions. …
We use both new and archival ALMA data of three energy lines each of CN and HCN to explore intensity ratios in dense gas in NGC 3256, NGC 7469, and IRAS 13120-5453. The HCN (3-2)/HCN (1-0) intensity ratio varies in NGC 3256 and NGC 7469, with superlinear trends of 1.53$\pm$0.07 and 1.55$\pm$0.05, respectively. We find an offset to higher HCN (3-2)/HCN (1-0) intensity ratios (~0.8) in IRAS 13120-5453 compared to NGC 3256 (~0.3-0.4) and NGC 7469 (~0.3-0.5). The HCN (4-3)/HCN (3-2) intensity ratio in NGC 7469 has a slope of 1.34$\pm$0.05. We attribute the variation within NGC 3256 to excitation a…
We have performed observations of water maser emission towards a sample of low-mass protostars, in order to investigate the properties of jets associated with the earliest stages of star formation and their interaction with the surrounding medium. The main aim is to measure the absolute positions and proper motions of the H_2O spots in order to investigate the kinematics of the region from where the jet is launched. We imaged the protostars in the nearby region NGC 1333-IRAS 4 in the water maser line at 22.2 GHz by using the VLBA in phase-reference mode at the milliarcsecond scale over four ep…
We present a multi-wavelength data analysis of IRAS 05463+2652 (hereafter I05463+2652) to study star formation mechanisms. A shell-like structure around I05463+2652 is evident in the Herschel column density map, which is not associated with any ionized emission. Based on the Herschel sub-millimeter images, several parsec-scale filaments (including two elongated filaments, "s-fl" and "nw-fl" having lengths of ~6.4 pc and ~8.8 pc, respectively) are investigated in I05463+2652 site. Herschel temperature map depicts all these features in a temperature range of ~11-13 K. 39 clumps are identified an…
Although deuterium enrichment of water may provide an essential piece of information in the understanding of the formation of comets and protoplanetary systems, only a few studies up to now have aimed at deriving the HDO/H2O ratio in low-mass star forming regions. Previous studies of the molecular deuteration toward the solar-type class 0 protostar, IRAS 16293-2422, have shown that the D/H ratio of water is significantly lower than other grain-surface-formed molecules. It is not clear if this property is general or particular to this source. In order to see if the results toward IRAS 16293-242…
The Helix Nebula (NGC 7293) is the closest planetary nebulae. Therefore, it is an ideal template for photochemical studies at small spatial scales in planetary nebulae. We aim to study the spatial distribution of the atomic and the molecular gas, and the structure of the photodissociation region along the western rims of the Helix Nebula as seen in the submillimeter range with Herschel. We use 5 SPIRE FTS pointing observations to make atomic and molecular spectral maps. We analyze the molecular gas by modeling the CO rotational lines using a non-local thermodynamic equilibrium (non-LTE) radiat…
We present the analysis of the physical properties of the interstellar medium (ISM) in the nearby early-type galaxy NGC 3665, based on the far-infrared (FIR) photometric and spectroscopic data as observed by the Herschel Space Observatory. The fit to the spectral energy distribution reveals a high dust content in the galaxy, with the dust-to-stellar mass ratio of $M_{\rm dust}$/$M_\ast$ $\sim$ 1.1 $\times$ 10$^{-4}$ that is nearly three times larger than the mean value of local S0+S0a galaxies. For the ionized regions (H~\textsc{ii} regions), the electron density (n$_e$) is around 49.5 $\pm$ 1…
NGC1569 has some of the most vigorous star formation among nearby galaxies. It hosts two super star clusters (SSCs) and has a higher star formation rate (SFR) per unit area than other starburst dwarf galaxies. Extended emission beyond the galaxy's optical body is observed in warm and hot ionised and atomic hydrogen gas; a cavity surrounds the SSCs. We aim to understand the impact of the massive star formation on the surrounding interstellar medium in NGC1569 through a study of its stellar and dust properties. We use Herschel and ancillary multiwavelength observations, from the ultraviolet to t…
The Odin satellite is now into its twentieth year of operation, much surpassing its design life of two years. One of its major pursuits was the search for and study of H2O in the Solar System and the Milky Way galaxy. Herschel has observed the central region of NGC 1365 in two positions, and both its SPIRE and PACS observations are available in the Herschel Science Archive. Herschel PACS images have been produced of the 70 and 160 micron infrared emission from the whole galaxy, and also of the cold dust distribution as obtained from the ratio of the 160 to 70 micron images. The Herschel SPIRE …
We present the first extragalactic detections of several CH rotational transitions in the far-infrared (FIR) in four nearby galaxies: NGC 1068, Arp 220, M 82 and NGC 253 using the \textit{Herschel Space Observatory}. The CH lines in all four galaxies are a factor of 2 - 4 brighter than the adjacent HCN and HCO+ J = 6-5 lines (also detected in the same spectra). In the star formation dominated galaxies, M 82, NGC 253 and Arp 220, the CH/CO abundance ratio is low (1e-5), implying that the CH is primarily arising in diffuse and translucent gas where the chemistry is driven by UV radiation as foun…
We investigate the physics and chemistry of the gas and dust in dense photon-dominated regions (PDRs), along with their dependence on the illuminating UV field. Using Herschel-HIFI observations, we study the gas energetics in NGC 7023 in relation to the morphology of this nebula. NGC 7023 is the prototype of a PDR illuminated by a B2V star and is one of the key targets of Herschel. Our approach consists in determining the energetics of the region by combining the information carried by the mid-IR spectrum (extinction by classical grains, emission from very small dust particles) with that of th…
We perform a comprehensive analysis of the planetary nebula (PN) NGC6781 to investigate the physical conditions of each of its ionized, atomic, and molecular gas and dust components and the object's evolution, based on panchromatic observational data ranging from UV to radio. Empirical nebular elemental abundances, compared with theoretical predictions via nucleosynthesis models of asymptotic giant branch (AGB) stars, indicate that the progenitor is a solar-metallicity, 2.25-3.0 Msun initial-mass star. We derive the best-fit distance of 0.46 kpc by fitting the stellar luminosity (as a function…
We present a detailed analysis of deep far-infrared observations of the nearby edge-on star-forming galaxy NGC 4631 obtained with the Herschel Space Observatory. Our PACS images at 70 and 160 um show a rich complex of filaments and chimney-like features that extends up to a projected distance of 6 kpc above the plane of the galaxy. The PACS features often match extraplanar Halpha, radio-continuum, and soft X-ray features observed in this galaxy, pointing to a tight disk-halo connection regulated by star formation. On the other hand, the morphology of the colder dust component detected on large…
We aim at deriving the molecular abundances and temperatures of the hot molecular cores in the high-mass star-forming region NGC 6334I and consequently deriving their physical and astrochemical conditions. In the framework of the Herschel guaranteed time key program CHESS, NGC 6334I is investigated by using HIFI aboard the Herschel Space Observatory. A spectral line survey is carried out in the frequency range 480-1907 GHz, and auxiliary interferometric data from the SMA in the 230 GHz band provide spatial information for disentangling the different physical components contributing to the HIFI…
Emission from high-J CO lines in galaxies has long been proposed as a tracer of X-ray dominated regions (XDRs) produced by AGN. Of particular interest is the question of whether the obscuring torus, which is required by AGN unification models, can be observed via high-J CO cooling lines. Here we report on the analysis of a deep Herschel-PACS observation of an extremely high J CO transition (40-39) in the Seyfert 2 galaxy NGC 1068. The line was not detected, with a derived 3$σ$ upper limit of $2 \times 10^{-17}\,\text{W}\,\text{m}^{-2}$. We apply an XDR model in order to investigate whether the…
Analysis of all-sky Planck submillimetre observations and the IRAS 100um data has led to the detection of a population of Galactic cold clumps. The clumps can be used to study star formation and dust properties in a wide range of Galactic environments. Our aim is to measure dust spectral energy distribution (SED) variations as a function of the spatial scale and the wavelength. We examine the SEDs at large scales using IRAS, Planck, and Herschel data. At smaller scales, we compare with JCMT/SCUBA-2 850um maps with Herschel data that are filtered using the SCUBA-2 pipeline. Clumps are extracted…
