Search

Nitrogen-bearing complex organic molecules have been commonly detected in the gas phase but not yet in interstellar ices. This has led to the long-standing question of whether these molecules form in the gas phase or in ices. $\textit{James Webb}$ Space Telescope ($\textit{JWST}$) offers the sensitivity, spectral resolution, and wavelength coverage needed to detect them in ices and investigate whether their abundance ratios are similar in gas and ice. We report the first tentative detection of CH$_3$CN, C$_2$H$_5$CN, and the simple molecule, N$_2$O, based on the CN-stretch band in interstellar ices toward three (HOPS 153, HOPS 370, and IRAS 20126+4104) out of the five protostellar systems observed as part of the Investigating Protostellar Accretion (IPA) GO program with $\textit{JWST}$-NIRSpec. We also provide upper limits for the two other sources with smaller luminosities in the sample. We detect OCN$^-$ in the ices of all sources with typical CH$_3$CN/OCN$^-$ ratios of around 1. Ice and gas column density ratios of the nitrogen-bearing species with respect to each other are better matched than those with respect to methanol, which are a factor of ${\sim}5$ larger in the ices than the gas. We attribute the elevated ice column densities with respect to methanol to the difference in snowline locations of nitrogen-bearing molecules and of methanol, biasing the gas-phase observations toward fewer nitrogen-bearing molecules. Moreover, we find tentative evidence for enhancement of OCN$^-$, CH$_3$CN, and C$_2$H$_5$CN in warmer ices, although formation of these molecules likely starts along with methanol in the cold prestellar phase. Future surveys combining NIRSpec and MIRI, and additional laboratory spectroscopic measurements of C$_2$H$_5$CN ice, are necessary for robust detection and conclusions on the formation history of complex cyanides., Comment: Accepted for publication in A&A

We present a multi-wavelength study of the molecular gas properties of a sample of local Seyfert 2 galaxies to assess if, and to what extent, the presence of an active galactic nucleus (AGN) can affect the Interstellar Medium (ISM) properties in a sample of 33 local Seyfert 2 galaxies. We compare the molecular gas content (MH2), derived from new and archival low-J CO line measurements of a sample of AGN and a control sample of star-forming galaxies (SFGs). Both the AGN and the control sample are characterised in terms of host-galaxy properties (e.g., stellar and dust masses, Mstar and Mdust, respectively; and star formation rate, SFR). We also investigate the effect of AGN activity onto the emission of polycyclic aromatic hydrocarbon (PAH) molecules in the mid-infrared (MIR), a waveband where the dust-reprocessed emission from the obscured AGN contributes the most. The AGN hosted in less massive galaxies (i.e., log(Mstar/Msun)<10.5; log(Mdust/Msun)<7.5) show larger molecular gas content with respect to SFGs matched in stellar and dust mass. When comparing their depletion time(tdep~MH2/SFR), AGN show tdep~0.3-1.0 Gyr, similar to those observed in the control sample of SFGs. Seyfert 2 galaxies show fainter PAH luminosity at increasingly larger dominance of the nuclear activity in the MIR. We find no clear evidence for a systematic reduction of the molecular gas reservoir at galactic scale in Seyfert galaxies with respect to SFGs. This is in agreement with recent studies showing that molecular gas content only is reduced in regions of sub-kpc size, where the emission from the accreting supermassive black hole dominates. Nonetheless, we show that the impact of AGN activity on the ISM is clearly visible as suppression of the PAH luminosity., Comment: Accepted for publication by A&A. 22 pages, 9 figures, 3 tables. APEX spectra available through CDS archive

We aim to characterize the outflow properties of a sample of early Class 0 phase low-mass protostars in Orion first identified by the Herschel Space Observatory. We also look for signatures of infall in key molecular lines. CO $J$=3-2 and $J$=4-3 maps toward 16 very young Class 0 protostars were obtained using the Atacama Pathfinder EXperiment (APEX) telescope. We search the data for line wings indicative of outflows and calculate masses, velocities, and dynamical times for the outflows. We use additional HCO$^+$, H$^{13}$CO$^+$, and NH$_3$ lines to look for infall signatures toward the protostars. We estimate the outflow masses, forces, and mass-loss rates based on the CO $J$=3-2 and $J$=4-3 line intensities for 8 sources with detected outflows. We derive upper limits for the outflow masses and forces of sources without clear outflow detections. The total outflow masses for the sources with clear outflow detections are in the range between 0.03 and 0.16 $M_\odot$ for CO $J$=3-2, and in the range between 0.02 and 0.10 $M_\odot$ for CO $J$=4-3. The outflow forces are in the range between $1.57\times10^{-4}$ and $1.16\times10^{-3}$ $M_\odot$ km s$^{-1}$ yr$^{-1}$ for CO $J$=3-2 and in the range between $1.14\times10^{-4}$ and $6.92\times10^{-4}$ $M_\odot$ km s$^{-1}$ yr$^{-1}$ for CO $J$=4-3. Nine protostars in our sample show asymmetric line profiles indicative of infall in HCO$^+$, compared to H$^{13}$CO$^+$ or NH$_3$. The outflow forces of the protostars in our sample show no correlation with the bolometric luminosity, unlike those found by some earlier studies for other Class 0 protostars. The derived outflow forces for the sources with detected outflows are similar to those found for other - more evolved - Class 0 protostars, suggesting that outflows develop quickly in the Class 0 phase., Comment: Accepted for publication in A&A

G351.776-0.527 is among the most massive, closest, and youngest filaments in the inner Galactic plane and therefore it is an ideal laboratory to study the kinematics of dense gas and mass replenishment on a large scale. In this paper, we present far-infrared (FIR) and submillimetre wavelength continuum observations combined with spectroscopic C$^{18}$O (2-1) data of the entire region to study its temperature, mass distribution, and kinematics. The structure is composed of a main elongated region with an aspect ratio of $\sim 23$, which is associated with a network of filamentary structures. The main filament has a remarkably constant width of 0.2 pc. The total mass of the network (including the main filament) is $\geq 2600$ M$_\odot$, while we estimate a mass of $\sim 2000$ M$_\odot$ for the main structure. Therefore, the network harbours a large reservoir of gas and dust that could still be accreted onto the main structure. From the analysis of the gas kinematics, we detect two velocity components in the northern part of the main filament. The data also reveal velocity oscillations in C$^{18}$O along the spine in the main filament and in at least one of the branches. Considering the region as a single structure, we find that it is globally close to virial equilibrium indicating that the entire structure is approximately in a stable state., Comment: 18 pages, 19 figures, accepted for publication in A&A

The nature of the far-IR source HOPS 108 has been a matter of debate in the last years. Previous radio observations detected a 3.6 cm source (VLA 12), coincident with HOPS 108, that was interpreted as a radio jet from this protostar. We present new multi-wavelength (0.7-5 cm), multi-configuration VLA observations as well as archive data (3.6 cm) that reveal VLA 12 as three knots of non-thermal emission, with HOPS 108 close to the central knot. We show that these knots have not been ejected by HOPS 108. We propose that the VLA 12 knots are actually part of a radio jet driven by VLA 11 (HOPS 370), a strong nearby source clearly elongated in the direction of the knots. The position of HOPS 108 in the path of the VLA 11-VLA 12 jet suggests an appealing new scenario: the triggered formation of HOPS 108 by the interaction of the jet with the surrounding medium., Comment: Proceedings of the Star Formation in Different Environments, ICISE, Quy Nhon, Vietnam, 2016, (eds. D. Johnstone, T. Hoang, F. Nakamura, Q. Nguyen-Luong, and J. T. Tranh Van)

We present key results from the Herschel Orion Protostar Survey (HOPS): spectral energy distributions (SEDs) and model fits of 330 young stellar objects, predominantly protostars, in the Orion molecular clouds. This is the largest sample of protostars studied in a single, nearby star-formation complex. With near-infrared photometry from 2MASS, mid- and far-infrared data from Spitzer and Herschel, and sub-millimeter photometry from APEX, our SEDs cover 1.2-870 $\mu$m and sample the peak of the protostellar envelope emission at ~100 $\mu$m. Using mid-IR spectral indices and bolometric temperatures, we classify our sample into 92 Class 0 protostars, 125 Class I protostars, 102 flat-spectrum sources, and 11 Class II pre-main-sequence stars. We implement a simple protostellar model (including a disk in an infalling envelope with outflow cavities) to generate a grid of 30400 model SEDs and use it to determine the best-fit model parameters for each protostar. We argue that far-IR data are essential for accurate constraints on protostellar envelope properties. We find that most protostars, and in particular the flat-spectrum sources, are well-fit. The median envelope density and median inclination angle decrease from Class 0 to Class I to flat-spectrum protostars, despite the broad range in best-fit parameters in each of the three categories. We also discuss degeneracies in our model parameters. Our results confirm that the different protostellar classes generally correspond to an evolutionary sequence with a decreasing envelope infall rate, but the inclination angle also plays a role in the appearance, and thus interpretation, of the SEDs., Comment: Accepted by ApJS; 87 pages; 2 online-only figure sets; corrected typos and other minor fixes

The formation of massive stars and their arrival on the zero-age main-sequence occurs hidden behind dense clouds of gas and dust. In the giant Hii region NGC 3603, the radiation of a young cluster of OB stars has dispersed dust and gas in its vicinity. At a projected distance of 2:5 pc from the cluster, a bright mid-infrared (mid-IR) source (IRS 9A) had been identified as a massive young stellar object (MYSO), located on the side of a molecular clump (MM2) of gas facing the cluster. We investigated the physical conditions in MM2, based on APEX sub-mm observations using the SABOCA and SHFI instruments, and archival ATCA 3 mm continuum and CS spectral line data. We resolved MM2 into several compact cores, one of them closely associated with IRS 9A. These are likely infrared dark clouds as they do not show the typical hot-core emission lines and are mostly opaque against the mid-IR background. The compact cores have masses of up to several hundred times the solar mass and gas temperatures of about 50 K, without evidence of internal ionizing sources. We speculate that IRS 9A is younger than the cluster stars, but is in an evolutionary state after that of the compact cores.

The Orion cloud complex presents a variety of star formation mechanisms and properties and it is still one of the most intriguing targets for star formation studies. We present VISTA/VIRCAM near-infrared observations of the L1630N star forming region, including the stellar clusters NGC 2068 and NGC 2071, in the Orion molecular cloud B and discuss them in combination with Spitzer data. We select 186 young stellar object (YSO) candidates in the region on the basis of multi-colour criteria, confirm the YSO nature of the majority of them using published spectroscopy from the literature, and use this sample to investigate the overall star formation properties in L1630N. The K-band luminosity function of L1630N is remarkably similar to that of the Trapezium cluster, i.e., it presents a broad peak in the range 0.3-0.7 M$_\odot$ and a fraction of sub-stellar objects of $\sim$20%. The fraction of YSOs still surrounded by disk/envelopes is very high ($\sim$85%) compared to other star forming regions of similar age (1-2 Myr), but includes some uncertain corrections for diskless YSOs. Yet, a possibly high disk fraction together with the fact that 1/3 of the cloud mass has a gas surface density above the threshold for star formation ($\sim$129 M$_\odot$ pc$^{-2}$), points towards a still on-going star formation activity in L1630N. The star formation efficiency (SFE), star formation rate (SFR) and density of star formation of L1630N are within the ranges estimated for galactic star forming regions by the Spitzer "core to disk" and "Gould's Belt" surveys. However, the SFE and SFR are lower than the average value measured in the Orion A cloud and, in particular, lower than that in the southern regions of L1630. This might suggest different star formation mechanisms within the L1630 cloud complex., Comment: 22 pages, 9 figures

A major goal of the Atacama Large Millimeter/submillimeter Array (ALMA) is to make accurate images with resolutions of tens of milliarcseconds, which at submillimeter (submm) wavelengths requires baselines up to ~15 km. To develop and test this capability, a Long Baseline Campaign (LBC) was carried out from September to late November 2014, culminating in end-to-end observations, calibrations, and imaging of selected Science Verification (SV) targets. This paper presents an overview of the campaign and its main results, including an investigation of the short-term coherence properties and systematic phase errors over the long baselines at the ALMA site, a summary of the SV targets and observations, and recommendations for science observing strategies at long baselines. Deep ALMA images of the quasar 3C138 at 97 and 241 GHz are also compared to VLA 43 GHz results, demonstrating an agreement at a level of a few percent. As a result of the extensive program of LBC testing, the highly successful SV imaging at long baselines achieved angular resolutions as fine as 19 mas at ~350 GHz. Observing with ALMA on baselines of up to 15 km is now possible, and opens up new parameter space for submm astronomy., Comment: 11 pages, 7 figures, 2 tables; accepted for publication in the Astrophysical Journal Letters; this version with small changes to affiliations

Contemporary theory holds that massive stars gather mass during their initial phases via accreting disk-like structures. However, conclusive evidence for disks has remained elusive for the most massive young objects. This is mainly due to significant observational challenges. Incisive studies, even targeting individual objects, are therefore relevant to the progression of the field. NGC 3603 IRS 9A* is a young massive stellar object still surrounded by an envelope of molecular gas. Previous mid-infrared observations with long-baseline interferometry provided evidence for a disk of 50 mas diameter at its core. This work aims at a comprehensive study of the physics and morphology of IRS 9A at near-infrared wavelengths. New sparse aperture masking interferometry data taken with NACO/VLT at Ks and Lp filters were obtained and analysed together with archival CRIRES spectra of the H2 and BrG lines. The calibrated visibilities recorded at Ks and Lp bands suggest the presence of a partially resolved compact object of 30 mas at the core of IRS 9A, together with the presence of over-resolved flux. The spectroastrometric signal of the H2 line shows that this spectral feature proceeds from the large scale extended emission (300 mas) of IRS 9A, while the BrG line appears to be formed at the core of the object (20 mas). This scenario is consistent with the brightness distribution of the source for near- and mid-infrared wavelengths at various spatial scales. However, our model suffers from remaining inconsistencies between SED modelling and the interferometric data. Moreover, the BrG spectroastrometric signal indicates that the core of IRS 9A exhibits some form of complexity such as asymmetries in the disk. Future high-resolution observations are required to confirm the disk/envelope model and to flesh out the details of the physical form of the inner regions of IRS 9A., Comment: Accepted to be published in Astronomy & Astrophysics, 13 pages, 14 figures

The present study aims at characterizing the massive star forming region G35.20N, which is found associated with at least one massive outflow and contains multiple dense cores, one of them recently found associated with a Keplerian rotating disk. We used ALMA to observe the G35.20N region in the continuum and line emission at 350 GHz. The observed frequency range covers tracers of dense gas (e.g. H13CO+, C17O), molecular outflows (e.g. SiO), and hot cores (e.g. CH3CN, CH3OH). The ALMA 870 um continuum emission map reveals an elongated dust structure (0.15 pc long and 0.013 pc wide) perpendicular to the large-scale molecular outflow detected in the region, and fragmented into a number of cores with masses 1-10 Msun and sizes 1600 AU. The cores appear regularly spaced with a separation of 0.023 pc. The emission of dense gas tracers such as H13CO+ or C17O is extended and coincident with the dust elongated structure. The three strongest dust cores show emission of complex organic molecules characteristic of hot cores, with temperatures around 200 K, and relative abundances 0.2-2x10^(-8) for CH3CN and 0.6-5x10^(-6) for CH3OH. The two cores with highest mass (cores A and B) show coherent velocity fields, with gradients almost aligned with the dust elongated structure. Those velocity gradients are consistent with Keplerian disks rotating about central masses of 4-18 Msun. Perpendicular to the velocity gradients we have identified a large-scale precessing jet/outflow associated with core B, and hints of an east-west jet/outflow associated with core A. The elongated dust structure in G35.20N is fragmented into a number of dense cores that may form massive stars. Based on the velocity field of the dense gas, the orientation of the magnetic field, and the regularly spaced fragmentation, we interpret this elongated structure as the densest part of a 1D filament fragmenting and forming massive stars., Comment: 24 pages, 26 figures, accepted for publication in Astronomy and Astrophysics (abstract modified to fit arXiv restrictions)

We use mid-infrared to submillimeter data from the Spitzer, Herschel, and APEX telescopes to study the bright sub-mm source OMC-2 FIR 4. We find a point source at 8, 24, and 70 $\mu$m, and a compact, but extended source at 160, 350, and 870 $\mu$m. The peak of the emission from 8 to 70 $\mu$m, attributed to the protostar associated with FIR 4, is displaced relative to the peak of the extended emission; the latter represents the large molecular core the protostar is embedded within. We determine that the protostar has a bolometric luminosity of 37 Lsun, although including more extended emission surrounding the point source raises this value to 86 Lsun. Radiative transfer models of the protostellar system fit the observed SED well and yield a total luminosity of most likely less than 100 Lsun. Our models suggest that the bolometric luminosity of the protostar could be just 12-14 Lsun, while the luminosity of the colder (~ 20 K) extended core could be around 100 Lsun, with a mass of about 27 Msun. Our derived luminosities for the protostar OMC-2 FIR 4 are in direct contradiction with previous claims of a total luminosity of 1000 Lsun (Crimier et al 2009). Furthermore, we find evidence from far-infrared molecular spectra (Kama et al. 2013, Manoj et al. 2013) and 3.6 cm emission (Reipurth et al 1999) that FIR 4 drives an outflow. The final stellar mass the protostar will ultimately achieve is uncertain due to its association with the large reservoir of mass found in the cold core., Comment: Accpeted by ApJ, 17 pages, 11 figures

We report on ALMA observations of continuum and molecular line emission with 0.4" resolution towards the high-mass star forming region G35.20-0.74 N. Two dense cores are detected in typical hot-core tracers, such as CH3CN, which reveal velocity gradients. In one of these cores, the velocity field can be fitted with an almost edge-on Keplerian disk rotating about a central mass of 18 Msun. This finding is consistent with the results of a recent study of the CO first overtone bandhead emission at 2.3mum towards G35.20-0.74 N. The disk radius and mass are >2500 au and 3 Msun. To reconcile the observed bolometric luminosity (3x10^4 Lsun) with the estimated stellar mass of 18 Msun, we propose that the latter is the total mass of a binary system., Comment: 5 pages, 4 figures, accepted for publication in Astronomy and Astrophysics Letters

We used the Atacama Pathfinder Experiment (APEX) 12 m telescope to observe the J_KaKc=3_03-2_02, 3_22-2_21, and 3_21-2_20 transitions of para-H_2CO at 218 GHz simultaneously to determine kinetic temperatures of the dense gas in the central molecular zone (CMZ) of our Galaxy. The map extends over approximately 40 arcmin x 8 arcmin (~100x20 pc^2) along the Galactic plane with a linear resolution of 1.2 pc. The strongest of the three lines, the H_2CO (3_03-2_02) transition, is found to be widespread, and its emission shows a spatial distribution similar to ammonia. The relative abundance of para-H_2CO is 0.5-1.2 10^{-9}, which is consistent with results from lower frequency H_2CO absorption lines. Derived gas kinetic temperatures for individual molecular clouds range from 50 K to values in excess of 100 K. While a systematic trend toward (decreasing) kinetic temperature versus (increasing) angular distance from the Galactic center (GC) is not found, the clouds with highest temperature (T_kin > 100 K) are all located near the nucleus. For the molecular gas outside the dense clouds, the average kinetic temperature is 65+/-10 K. The high temperatures of molecular clouds on large scales in the GC region may be driven by turbulent energy dissipation and/or cosmic-rays instead of photons. Such a non-photon-driven thermal state of the molecular gas provides an excellent template for the more distant vigorous starbursts found in ultraluminous infrared galaxies (ULIRGs)., Comment: 23 pages, 11 figures, A&A in press

Infrared dark clouds are massive, dense clouds seen in extinction against the IR Galactic background. Many of these objects appear to be on the verge of star and star cluster formation. Our aim is to understand the physical properties of IRDCs in very early evolutionary phases. We selected the filamentary IRDC G351.77 - 0.51, which is remarkably IR quiet at 8{\mu}m. As a first step, we observed mm dust continuum emission and rotational lines of moderate and dense gas tracers to characterise different condensations along the IRDC and study the velocity field of the filament. Our initial study confirms coherent velocity distribution along the infrared dark cloud ruling out any coincidental projection effects. Excellent correlation between MIR extinction, mm continuum emission and gas distribution is found. Large-scale turbulence and line profiles throughout the filament is indicative of a shock in this cloud. Excellent correlation between line width, and MIR brightness indicates turbulence driven by local star formation., Comment: accepted for publication in A&A

The NGC 1999 reflection nebula features a dark patch with a size of ~10,000 AU, which has been interpreted as a small, dense foreground globule and possible site of imminent star formation. We present Herschel PACS far-infrared 70 and 160mum maps, which reveal a flux deficit at the location of the globule. We estimate the globule mass needed to produce such an absorption feature to be a few tenths to a few Msun. Inspired by this Herschel observation, we obtained APEX LABOCA and SABOCA submillimeter continuum maps, and Magellan PANIC near-infrared images of the region. We do not detect a submillimer source at the location of the Herschel flux decrement; furthermore our observations place an upper limit on the mass of the globule of ~2.4x10^-2 Msun. Indeed, the submillimeter maps appear to show a flux depression as well. Furthermore, the near-infrared images detect faint background stars that are less affected by extinction inside the dark patch than in its surroundings. We suggest that the dark patch is in fact a hole or cavity in the material producing the NGC 1999 reflection nebula, excavated by protostellar jets from the V 380 Ori multiple system., Comment: accepted for the A&A Herschel issue; 7 pages

We present 70 and 160 micron Herschel science demonstration images of a field in the Orion A molecular cloud that contains the prototypical Herbig-Haro objects HH 1 and 2, obtained with the Photodetector Array Camera and Spectrometer (PACS). These observations demonstrate Herschel's unprecedented ability to study the rich population of protostars in the Orion molecular clouds at the wavelengths where they emit most of their luminosity. The four protostars previously identified by Spitzer 3.6-40 micron imaging and spectroscopy are detected in the 70 micron band, and three are clearly detected at 160 microns. We measure photometry of the protostars in the PACS bands and assemble their spectral energy distributions (SEDs) from 1 to 870 microns with these data, Spitzer spectra and photometry, 2MASS data, and APEX sub-mm data. The SEDs are fit to models generated with radiative transfer codes. From these fits we can constrain the fundamental properties of the protostars. We find luminosities in the range 12-84 L_sun and envelope densities spanning over two orders of magnitude. This implies that the four protostars have a wide range of envelope infall rates and evolutionary states: two have dense, infalling envelopes, while the other two have only residual envelopes. We also show the highly irregular and filamentary structure of the cold dust and gas surrounding the protostars as traced at 160 microns., Comment: 6 pages, 4 figures, accepted for publication in the A&A Herschel special issue

Molecular outflows from high-mass young stellar objects provide an excellent way to study the star formation process, and investigate if they are scaled-up versions of their low-mass counterparts. We selected the nearby massive star forming region IRAS 17233-3606 in order to study the kinematics and physics along the molecular outflow(s) originating from this source. We observed IRAS 17233-3606 in CO, a typical tracer of gas associated with molecular outflow, with the Submillimeter Array in the (2-1) transition, and with the APEX telescope in the higher excitation (6-5) line. Additional infrared H2 observations were performed with the UKIRT telescope. The CO data were analysed using a LVG approach. Our data resolve the previously detected molecular outflow in at least three different components, one of them with a high collimation factor ~4, and characterised by emission at extremely high velocities (|v-v_{LSR}|>120 km s^{-1}). The estimate of the kinematical outflow parameters are typical of massive YSOs, and in agreement with the measured bolometric luminosity of the source. The kinematic ages of the flows are in the range 10^2-10^3 yr, and therefore point to young objects that still did not reach the main sequence., Comment: accepted for publication in A&A

We present wide-field near-IR images of Orion A. K and H2 1-0S(1) images of a contiguous 8 sqr degree region are compared to photometry from Spitzer and dust-continuum maps obtained with MAMBO and SCUBA. We also measure proper motions for H2 features in 33 outflows. We increase the number of known H2 outflows in Orion A to 116. A total of 111 H2 flows were observed with Spitzer; outflow sources are identified for at least 72 of them. The MAMBO 1200 micron maps cover 97 H2 flows; 57 of them are associated with Spitzer sources and dust cores or extended emission. The H2 jets are widely distributed and randomly orientated; the jets do not appear to be orthogonal to large-scale filaments or even to the small-scale cores. Moreover, H2 jet lengths and opening angles are not obviously correlated with indicators of outflow source age - source spectral index or (sub)millimetre core flux. We demonstrate that H2 jet sources are predominantly protostellar with flat or positive spectral indices, rather than disk-excess (or T Tauri) stars. Most protostars in molecular cores drive H2 outflows. However, not all molecular cores are associated with protostars or H2 jets. On statistical grounds, the H2 jet phase may be marginally shorter than the protostellar phase, though must be considerably shorter than the prestellar phase. In terms of their spectral index, H2 jet sources are indistinguishable from protostars. The few true protostars without H2 jets are almost certainly more evolved than their H2-jet-driving counterparts. We also find that protostars that power molecular outflows are no more (nor no less) clustered than protostars that do not. The H2 emission regions in outflows from young stars clearly weaken and fade very quickly, before the source evolves from protostar to pre-main-sequence star., Comment: Avccepted by A&A. Appendix figures (and high-res. version of paper) available from http://www.jach.hawaii.edu/~cdavis/

PdBI high-spatial resolution CO observations combined with near-infrared H2 data disentangle at least 7 (maybe even 9) molecular outflows in the massive star-forming region IRAS19410+2336. Position-velocity diagrams of the outflows reveal Hubble-like relationships similar to outflows driven by low-mass objects. Estimated accretion rates are of the order 10^-4 Msun/yr, sufficiently high to overcome the radiation pressure and form massive stars via disk-mediated accretion processes. The single-dish large-scale mm continuum cores fragment into several compact condensations at the higher spatial resolution of the PdBI which is expected due to the clustering in massive star formation. While single-dish data give a simplified picture of the source, sufficiently high spatial resolution resolves the structures into outflows resembling those of low-mass star-forming cores. We interpret this as further support for the hypothesis that massive stars do form via disk-accretion processes similar to low-mass stars., Comment: 10 pages, 4 figures, higher resolution version of images at http://cfa-www.harvard.edu/~hbeuther/. A&A, accepted

We present a wide-field survey of the young open cluster IC348 for molecular H2 outflows. Outflow activity is only found at its south-western limit, where a new subcluster of embedded sources is in an early phase of its formation. If the IC348 cluster had been built up by such subclusters forming at different times, this could explain the large age-spread that Herbig (1998) found for the IC348 member stars. In addition to several compact groups of H2 knots, our survey reveals a large north-south oriented outflow, and we identify the newly discovered far-infrared and mm-object IC348MMS as its source. New deep images in the 1-0 S(1) line of molecular hydrogen trace the HH211 jet and counterjet as highly-collimated chains of knots, resembling the interferometric CO and SiO jets. This jet system appears rotated counter-clockwise by about 3 degrees with respect to the prominent H2 bow shocks. Furthermore, we resolve HH211-mm as a double point-like source in the mm-continuum., Comment: 10 pages, 9 figures, accepted for publication in ApJ

We report the detection of hard X-ray emission (>2 keV) from a number of point sources associated with the very young massive star-forming region IRAS 19410+2336. The X-ray emission is detected from several sources located around the central and most deeply embedded mm continuum source, which remains undetected in the X-ray regime. All X-ray sources have K-band counterparts, and those likely belonging to the evolving massive cluster show near-infrared colors in the 2MASS data indicative of pre-main-sequence stages. The X-ray luminosities around 10^{31} erg/s are at the upper end of luminosities known for low-mass pre-main-sequence sources, and mass estimates based on the infrared data indicate that at least some of the X-ray detected sources are intermediate-mass objects. Therefore, we conclude that the X-ray emission is due to intermediate-mass pre-main-sequence Herbig Ae/Be stars or their precursors. The emission process is possibly due to magnetic star-disk interaction as proposed for their low-mass counterparts., Comment: 10 pages, 5 figures, A&A accepted

We describe in this paper the ROSAT Ultra Deep Survey (UDS), an extension of the ROSAT Deep Survey (RDS) in the Lockman Hole. The UDS reaches a flux level of 1.2 x 10E-15 erg/cm2/s in 0.5-2.0 keV energy band, a level ~4.6 times fainter than the RDS. We present nearly complete spectroscopic identifications (90%) of the sample of 94 X-ray sources based on low-resolution Keck spectra. The majority of the sources (57) are broad emission line AGNs (type I), whereas a further 13 AGNs show only narrow emission lines or broad Balmer emission lines with a large Balmer decrement (type II AGNs) indicating significant optical absorption. The second most abundant class of objects (10) are groups and clusters of galaxies (~11%). Further we found five galactic stars and one ''normal'' emission line galaxy. Eight X-ray sources remain spectroscopically unidentified. The photometric redshift determination indicates in three out of the eight sources the presence of an obscured AGN in the range of 1.2 < z < 2.7. These objects could belong to the long-sought population of type 2 QSOs, which are predicted by the AGN synthesis models of the X-ray background. Finally, we discuss the optical and soft X-ray properties of the type I AGN, type II AGN, and groups and clusters of galaxies, and the implications to the X-ray backround., Comment: 26 pages, 8 figures (finding charts and spectra in JPEG), accepted for publication by A & A

We have identified twenty-seven candidate very low mass members of the relatively young Alpha Persei open cluster from a six square degree CCD imaging survey. Based on their I magnitudes and the nominal age and distance to the cluster, these objects should have masses less than 0.1 Msunif they are cluster members. We have subsequently obtained intermediate resolution spectra of seventeen of these objects using the Keck II telescope and LRIS spectrograph. We have also obtained near-IR photometry for many of the stars. Our primary goal was to determine the location of the "lithium depletion boundary" and hence to derive a precise age for the cluster. We detect lithium with equivalent widths greater than or equal to 0.4 \AA in five of the program objects. We have constructed a color-magnitude diagram for the faint end of the Alpha Persei main sequence. These data allow us to accurately determine the Alpha Persei single-star lithium depletion boundary at M(I$_C$) = 11.47, M(Bol) = 11.42, (R-I)$_{C0}$ = 2.12, spectral type M6.0. By reference to theoretical evolutionary models, this converts fairly directly into an age for the Alpha Persei cluster of 90 $\pm$ 10 Myr. At this age, the two faintest of our spectroscopically confirmed members should be sub-stellar (i.e., brown dwarfs) according to theoretical models., Comment: Accepted ApJ