We present nine epochs of Hubble Space Telescope optical imaging of the bipolar outflow from the pre-main sequence binary XZ Tauri. Our data monitors the system from 1995-2005 and includes emission line images of the flow. The northern lobe appears to be a succession of bubbles, the outermost of which expanded ballistically from 1995-1999 but in 2000 began to deform and decelerate along its forward edge. It reached an extent of 6" from the binary in 2005. A larger and fainter southern counterbubble was detected for the first time in deep ACS images from 2004. Traces of shocked emission are seen as far as 20" south of the binary. The bubble emission nebulosity has a low excitation overall, as traced by the [S II]/H-alpha line ratio, requiring a nearly comoving surrounding medium that has been accelerated by previous ejections or stellar winds.
Within the broad bubbles there are compact emission knots whose alignments and proper motions indicate that collimated jets are ejected from each binary component. The jet from the southern component, XZ Tau A, is aligned with the outflow axis of the bubbles and has tangential knot velocities of 70-200 km/s. Knots in the northern flow are seen to slow and brighten as they approach the forward edge of the outermost bubble. The knots in the jet from the other star, XZ Tau B, have lower velocities of ~100 km/s.
Comparing the properties AGN and Herbig-Haro jets can be a useful exercise for understanding the physical mechanisms at work in collimated outflows that propagate in such different environments. In the case of Herbig-Haro jets, the presence of emission lines in the spectra and the continuous evolution of the observation techniques greatly favor our knowledge of the physical parameters of the jets instead, for AGN jets, the process of constraining the jet parameters is hampered by the nature of the emission from these objects that is non-thermal. I will discuss how one cannot directly constrain…
Herbig-Haro jets often show some degree of curvature along their path, in many cases produced by the ram pressure of a side-wind. We present simulations of both laboratory and astrophysical curved jets and experimental results from laboratory experiments. We discuss the properties and similarities of the laboratory and astrophysical flow, which show the formation of internal shocks and working surfaces. In particular the results illustrate how the break-up of the bow-shock and clumps in the flow are produced without invoking jet variability; we also discuss how jet rotation reduces the growth …
The spectra of Herbig Haro objects are usually characteristic of ionization and excitation in shock-heated gas, whether an internal shock in an unsteady outflow or a bow shock interface with the interstellar medium. We examine the eastern-most shock -- the leading optically visible shock -- of a Herbig Haro outflow (HH 529) seen projected on the face of the Orion Nebula, using deep optical echelle spectroscopy, showing that the spectrum of this gas is consistent with photoionization by $θ^1$ Ori C. By modeling the emission lines, we determine a gas-phase abundance of Fe which is consistent wit…
Aims: We search for direct evidence of ongoing star formation by accretion in the Lagoon Nebula (M8), using optical wide-field narrow-band imaging obtained at La Silla Observatory. Methods: We examine [SII] and Halpha images for line-emission features that could be interpreted as signatures of outflow activity of the exciting sources. Results: We discover five new Herbig-Haro objects, study in detail their morphology and attempt to identify their potential driving sources among the population of T Tauri stars and embedded sources in the surroundings. Conclusions: The results reported here conc…
We report our new results from wide-field surveys of Herbig-Haro (HH) objects in the nearby star forming regions. The surveys covered approximately 56 degree in Perseus, Taurus, Orion, Monoceros, and other regions. Using refined techniques, we discovered in total 68 HH objects, of which 32 were in Perseus, 4 in Taurus, 13 in Orion, 18 in Monoceros, and 1 in S287 regions. The newly discovered HH objects demonstrate a great variety of morphological structures, including 5 jets, 7 arcs, 12 cirri or cirrus groups, 13 patches, and many knots. These objects provide a new comprehensive database for t…
Using Spitzer Space Telescope and Hubble Space Telescope observations of the superbubble N51D, we have identified three young stellar objects (YSOs) in dust globules, and made the first detection of a Herbig-Haro object outside the Galaxy. The spectral energy distributions of these YSOs suggest young massive stars with disk, envelope, and outflow cavities. The interstellar conditions are used to assess whether the star formation was spontaneous or induced by external pressure.
By using the flux ratio [FeII]8617/[OI]6300, we demonstrate that most of the interstellar dust grains survive in shocks associated with supernova remnants and Herbig-Haro objects. The [FeII]/[OI] flux ratio is sensitive to the gas-phase Fe/O abundance ratio, but is insensitive to the ionization state, temperature, and density of the gas. We calculate the [FeII]/[OI] flux ratio in shocks, and compare the results with the observational data. When only 20% of iron is in the gas phase, the models reproduce most successfully the observations. This finding is in conflict with the current consensus t…
HH 110 and HH 262 are two Herbig-Haro jets with rather peculiar, chaotic morphology. In the two cases, no source suitable to power the jet has been detected along the outflow, at optical or radio wavelengths. Both, previous data and theoretical models, suggest that these objects are tracing an early stage of an HH jet/dense cloud interaction. We present the first results of the integral field spectroscopy observations made with the PMAS spectrophotometer (with the PPAK configuration) of these two turbulent jets. New data of the kinematics in several characteristic HH emission lines are shown. …
We report here the discovery of a 30"-chain of embedded Herbig-Haro (HH) objects in the rho Ophiuchi dark cloud. These HH objects were first detected during a deep K_S-band observation (completeness magnitude for point source~19) made with NTT/SOFI. We confirm their nature with follow-up observations made with H_2 v=1-0 S(1) narrow-band filter. We argue that they belong to two different jets emanating from two Class I protostars: the main component of the recently resolved subarcsecond radio binary YLW15 (also called IRS43), and IRS54. We propose also to identify the [S II] knot HH224NW1 (Gome…
Herbig-Haro objects (HHOs) are caused by outflows from young objects. Since the outflow relies on mass accretion from a circumstellar disk, it indicates ongoing growth. Recent results of infrared observations yielded evidence for disks around brown dwarfs. This suggests that at least a certain fraction of brown dwarfs forms like stars. Thus, young sub-stellar objects might cause HHOs as well. We present selected results of a general survey for HHOs based on DSS-II plates and CCD images taken with the Tautenburg Schmidt telescope. Numerous young objects could be identified due to their associat…
Infrared photometry and spectroscopy covering a time span of a quarter century are presented for HD 31648 (MWC 480) and HD 163296 (MWC 275). Both are isolated Herbig Ae stars that exhibit signs of active accretion, including driving bipolar flows with embedded Herbig-Haro (HH) objects. HD 163296 was found to be relatively quiescent photometrically in its inner disk region, with the exception of a major increase in emitted flux in a broad wavelength region centered near 3 microns in 2002. In contrast, HD 31648 has exhibited sporadic changes in the entire 3-13 micron region throughout this span …
We have carried out an extensive observational study (from BIMA data) and made a preliminary theoretical investigation of the molecular gas around HH2. The molecular maps show a very complex morphological, kinematical and chemical structure. The overall main conclusion of this work confirms the findings of Paper I and II, by demonstrating that in addition to the strong photochemical effects caused by penetration of the UV photons from HH2 into molecular cloud, a range of complex radiative and dynamical interactions occur. Thus, despite the apparent `quiescent' nature of the molecular cloud ahe…
We report on initial results of our Spitzer Cycle 2 program to observe the young massive star R Mon and its associated HH 39 Herbig-Haro object in the mid-infrared. Our program used all instruments on-board Spitzer to obtain deep images with IRAC of the HH 39 complex and of R Mon and its surroundings, a deep image of HH 39 at 24 and 70 $μ$m with MIPS, and mid-infrared spectra with the SH, LH, and LL modules of IRS. The aim of this program is to study the physical links in a young massive star between accretion disk, outflows and jets, and sh ocks in the associated HH object. Our preliminary an…
It has been recently discovered that spatially separated Herbig-Haro objects, once considered unrelated, are linked within a chain that may extend for parsecs in either direction of the embedded protostar forming a "giant Herbig-Haro jet". Presently, several dozen of these giant flows have been detected and the best documented example, the HH~34 system, shows a systematic velocity decrease with distance on either side of the source. In this paper, we have modeled giant jets by performing fully three-dimensional simulations of overdense, radiatively cooling jets modulated with long-period (P $\…
Context. A molecular survey recently performed ahead of HH~2 supports the idea that the observed molecular enhancement is due to UV radiation from the HH object. Aims. The aim of the present work is to determine whether all HH objects with enhanced HCO$^+$ emission ahead of them also exhibit the same enhanced chemistry as HH~2. We thus observed several molecular lines at several positions ahead of five Herbig-Haro objects where enhanced HCO$^+$ emission was previously observed. Methods. We mapped the five Herbig-Haro objects using the IRAM-30 m. For each position we searched for more than one …
We present the results of a photographic and CCD imaging survey for Herbig-Haro (HH) objects in the L1630 and L1641 giant molecular clouds in Orion. The new HH flows were initially identified from a deep H-alpha film from the recently commissioned AAO/UKST H-alpha Survey of the southern sky. Our scanned H-alpha and broad band R images highlight both the improved resolution of the H-alpha survey and the excellent contrast of the H-alpha flux with respect to the broad band R. Comparative IVN survey images allow us to distinguish between emission and reflection nebulosity. Our CCD H-alpha, [SII],…
We have surveyed the inner 5' of the Orion Nebula by means of Halpha and [NII] Fabry-Perot imaging spectroscopy to present a kinematical study of the Herbig-Haro objects in the nebula. The objects studied in this work are HH 202, 203, 204, 529, 269 and other associated features. For HH 202 we find new features that, because of their high velocities (up to 100 km/seg) indicate the presence of an outflow that probably is a HH flow not catalogued previously. HH 202 could be only a part of this larger outflow. Large internal motions are found in the fainter regions of HH 203-204, as well as eviden…
We present high angular resolution (12"-24") and high sensitivity 12CO and 13CO J=2-1 and J=1-0 observations of the HH 1-2 outflow. The observations show the molecular counterpart, moving with a velocity of approx. 30 km/s, of the optical bipolar system driven by the VLA 1 embedded source. Along the optical jet there are certain regions where the molecular gas reaches deprojected velocities of 100-200 km/s, and that we interpret as the molecular jet. The bipolar CO outflow has a length of approx. 260" with a curved morphology towards the North where it extends beyond the HH 1 object (approx. 1…
[abridged] We present high resolution optical spectra of stars in Taurus-Auriga whose circumstellar environment suggests that they are less evolved than optically revealed T Tauri stars. Many of the stars are seen only via scattered light. These spectra are used to search for differences between stars which power Herbig-Haro flows and stars which do not, and to reassess the evolutionary state of so-called protostars (Class I stars) relative to optically revealed T Tauri stars (Class II stars). The stellar mass distribution of Class I stars is similar to that of Class II stars and includes 3 Cl…
We report high spectral resolution (R=20,000) measurements of the H2 1-0 S(1) line in Herbig-Haro Objects 38, 46/47, and 120. The long-slit spectra reveal complex velocity structure with evidence for bow-shock structures as well as prompt entrainment and shock heating of ambient molecular gas. Individual knots within HH 38 show distinct double peaked velocity stucture, consistent with that expected from spatially unresolved bow shocks. A portion of the HH 47A bow shock is resolved in our measurements, and the kinematics of the H2 trace closely that found for H-alpha emission. The evidence indi…
We report the discovery of a pair of large Herbig-Haro type structures roughly 10 arcminutes (1.3 pc) north-east and south-west of the source driving the well-known HH 46/47 Herbig-Haro jet in new deep emission-line images made using the Wide Field Imager on the ESO/MPG La Silla 2.2-m telescope. These new images suggest that the HH 46/47 outflow is much more extensive than previously assumed, extending over a total of 2.6 pc on the sky, or over 3 pc in space, when deprojected. HH 46/47 thus also belongs to the recently-discovered class of giant Herbig-Haro flows.
We present a CSO and BIMA molecular line survey of the dense, quiescent molecular environment ahead of HH2. The molecular gas is cold, 13 K, and moderately dense, 3x10^5 cm^-3. A total of 14 species has been detected (including different isotopes and deuterated species). The relative abundances of the clump are compared with other dense molecular environments, including quiescent dark clouds, and active low and high mass star forming regions. This comparison confirms the peculiar chemical composition of the quiescent gas irradiated by the HH objects. Thus, from this comparison, we found that t…
We present results from a study of molecular gas and dust in the vicinity of the Herbig Haro object HH2. Emission from the sub-mm continuum, 12CO and HCO+ was mapped with angular resolutions ranging from 14 arcsec to 5 arcsec (or 0.01pc at the distance of HH2). The continuum shows an extended dust clump of mass 3.8Msun and temperature 22K, located downstream of the bright optical HH knots. However, a compact emission peak lies within ~0.01pc of the low-excitation H2-prominent shocks, with a luminosity consistent with local heating by the outflow. The HCO+ emission shows two velocity components…
While there are many parsec-scale Herbig-Haro (HH) outflows known to be driven by low-mass young stars, few are associated with their intermediate mass counterparts. Here we present the discovery of five such bipolar outflows. Of these, LkHalpha 198, 1548C27 IRS1, LkHalpha 233 and LkHalpha 234 were previously known to possess small-scale HH flows, while no such activity was observed before near IRAS 19395+2313. The largest of the newly discovered outflows are seen in the vicinity of LkHalpha 234 and 1548C27 IRS1, and stretch (in projection) 8pc and 7.5pc respectively. LkHalpha 233 which was pr…
We present Halpha spectropolarimetry observations of a sample of 10 bright T Tauri stars, supplemented with new Herbig Ae/Be star data. A change in the linear polarisation across Halpha is detected in most of the T Tauri (9/10) and Herbig Ae (9/11) objects, which we interpret in terms of a compact source of line photons that is scattered off a rotating accretion disk. We find consistency between the position angle (PA) of the polarisation and those of imaged disk PAs from infrared and millimetre imaging and interferometry studies, probing much larger scales. For the Herbig Ae stars AB Aur, MWC…
(modified for brevity) It is important to determine whether the observed bow shocks in the working surfaces of Herbig-Haro outflows has lead to a destruction of dust grains and consequently to a change in the gas phase metal abundances (say of Fe) in the cooling regions of HH bow shocks. Detailed studies are currently available for only 5 HH outflows (Beck-Winchatz et al.\ 1996), due to the large observational and theoretical effort required to determine metal abundances in HH objects. Information about metal abundances in more HH objects is badly needed. We therefore use a very approximate me…
We report the discovery of a dozen Herbig-Haro jets illuminated by the Lyman continuum and/or softer far-ultraviolet radiation fields of nearby high mass stars. Five irradiated outflows lie in the outer parts of the Orion Nebula and seven lie near the reflection nebula NGC 1333 in the Perseus molecular cloud. We propose that the UV radiation field has eroded residual material left over from the formation of these young source stars. Many of the irradiated jets exhibit unusual C-shaped bending. In the outskirts of the Orion Nebula, most irradiated jets bend away from the core of the nebula. On …
Intermediate dispersion spectroscopic observations of 37 Herbig Ae/Be stars reveal that the equivalent widths of their [OI] 6300A and Halpha emission lines, are related to their near-infrared colours in the same fashion as the T-Tauri stars. Such a correlation strongly supports the idea that the winds from Herbig Ae/Be stars arise in the same manner as those from T-Tauri stars, i.e. through accretion driven mass-loss. We also find that the [OI] 6300A line luminosity correlates better with excess infrared luminosity than with stellar luminosities, again supporting the idea that Herbig Ae/Be win…
We present an infrared imaging study of the low-mass pre-main sequence binary system Haro 6-10. This system is one of a handful in which the optically-visible primary has the characteristics of a normal T Tauri star, while the secondary is a so-called "infrared companion" (IRC), a strongly extincted object which emits most of its luminosity in the infrared. A speckle holographic technique was used to produce nearly diffraction-limited images on three nights over a one-year period starting in late 1997. The images show that the IRC is obscured and surrounded by a compact, irregular, and variabl…
We present infrared echelle spectroscopy of three Herbig-Haro (HH) driving sources (SVS 13, B5-IRS 1 and HH 34 IRS) using Subaru-IRCS. The large diameter of the telescope and wide spectral coverage of the spectrograph allowed us to detect several H_2 and [Fe II] lines in the H- and K-bands. These include H_2 lines arising from v=1-3 and J=1-11, and [Fe II] lines with upper level energies of E/k=1.1-2.7x10^4 K. For all objects the outflow is found to have two velocity components: (1) a high-velocity (-70 to -130 km s^-1) component (HVC), seen in [Fe II] or H_2 emission and associated with a col…
In this paper we present detailed models of the vertical structure (temperature and density) of passive irradiated circumstellar disks around T Tauri and Herbig Ae/Be stars. In contrast to earlier work, we use full frequency- and angle-dependent radiative transfer instead of the usual moment equations. We find that this improvement of the radiative transfer has strong influence on the resulting vertical structure of the disk, with differences in temperature as large as 70 %. However, the spectral energy distribution (SED) is only mildly affected by this change. In fact, the SED compares reason…
We present VLT-FORS2 optical (5700 - 9400 A) spectroscopy of close (r < 1.5'') companions to three nearby (d < 200 pc) Herbig Ae/Be stars (HD 144432, HD 150193, KK Oph) and one T Tauri star (S CrA). We report the detection of Li I (6707 A) in absorption and emission lines (Halpha, Ca II triplet) in the spectra of the companions. Our observations strongly suggest that the companions are physically associated pre-main-sequence stars. The spectral type derived for the companions is K5Ve for HD 144432 B, F9Ve for HD 150193 B, and G6Ve for KK Oph B. S CrA A and B were observed simultaneously. The s…
We have used the 2.56m Nordic Optical Telescope (NOT) to observe two deep fields in L1641N, selected on the basis of previous shock studies, using the 2.12 micron transition of H2 (and a Ks filter to sample the continuum) for a total exposure time of 4.6 h (72 min Ks) in the overlapping region. The resulting high-resolution mosaic shows numerous new shocks and resolves many known shocks into multiple components. Using previous observations taken 9 years earlier we calculate a proper motion map and combine this with Spitzer 24 micron observations of the embedded young stars. The combined H2 mos…
We present spatially resolved near-IR spectroscopic observations of 15 young stars. Using a grism spectrometer behind the Keck Interferometer, we obtained an angular resolution of a few milli-arcseconds and a spectral resolution of 230, enabling probes of both gas and dust in the inner disks surrounding the target stars. We find that the angular size of the near-IR emission typically increases with wavelength, indicating hot, presumably gaseous material within the dust sublimation radius. Our data also clearly indicate Brackett-gamma emission arising from hot hydrogen gas, and suggest the pres…
We improve upon the radiative, hydrostatic equilibrium models of passive circumstellar disks constructed by Chiang & Goldreich (1997). New features include (1) account for a range of particle sizes, (2) employment of laboratory-based optical constants of representative grain materials, and (3) numerical solution of the equations of radiative and hydrostatic equilibrium within the original 2-layer (disk surface + disk interior) approximation. We explore how the spectral energy distribution (SED) of a face-on disk depends on grain size distributions, disk geometries and surface densities, and st…
We have used widely spaced in time Hubble Space Telescope images to determine tangential velocities of features associated with outflows from young stars. These observations were supplemented by groundbased telescope spectroscopy and from the resultant radial velocities, space velocities were determined for many outflows. Numerous new moving features were found and grouped into known and newly assigned Herbig Haro objects. It was found that stellar outflow is highly discontinuous, as frequently is the case, with long-term gaps of a few hundred years and that these outflow periods are marked by…
We have observed optical (Halpha and [SII]) and near-IR (S(1) line of H2) deep fields and taken optical spectra using the 2.56m NOT, as well as a near-UV deep field (U band) using the 3.58m NTT. In addition we present new SPITZER (IRAC and MIPS) mid-IR observations. We use previous Halpha and S(1) observations taken 15 and 9 years earlier to make proper motion maps. We then investigate the shock physics by matching our spectra with planar shock models. We discover six new HH objects in B335. From proper motions we find an optically bright, roughly E-W oriented group with high space velocities …
Aims: We search for PAH features towards T Tauri stars and compare them with surveys of Herbig Ae/Be stars. The presence and strength of the PAH features are interpreted with disk radiative transfer models exploring the PAH feature dependence on the incident UV radiation, PAH abundance and disk parameters. Methods: Spitzer Space Telescope 5-35 micron spectra of 54 pre-main sequence stars with disks were obtained, consisting of 38 T Tauri, 7 Herbig Ae/Be and 9 stars with unknown spectral type. Results: Compact PAH emission is detected towards at least 8 sources of which 5 are Herbig Ae/Be stars…
Our aim is to determine the presence and location of the emission from polycyclic aromatic hydrocarbons (PAHs) towards low and intermediate mass young stars with disks using large aperture telescopes. VLT-VISIR N-band spectra and VLT-ISAAC and VLT-NACO L-band spectra of 29 sources are presented, spectrally resolving the 3.3, 8.6, 11.2, and 12.6 micron PAH features. Spatial-extent profiles of the features and the continuum emission are derived and used to associate the PAH emission with the disks. The results are discussed in the context of recent PAH-emission disk models. The 3.3, 8.6, and 11.…
We present the results of HST/STIS and WFPC2 observations of LkHa 233 and its environment. LkHa233 is a Herbig Ae/Be star with a collimated bipolar jet. We investigate optical forbidden lines along the LkHa 233 jet to determine physical parameters of this jet (electron density n_e, hydrogen ionisation fraction x_e, electron temperature T_e, and mass density n_H). The knowledge of these parameters allows us a direct comparison of a jet from a Herbig star with those from T Tauri stars. The WFPC2 images in broad-band filters clearly show a dark lane caused either by a circumstellar disk or a dust…
We present new X-ray observations of the nearby Herbig Ae star HD 104237 (= DX Cha) with XMM-Newton, whose objective is to clarify the origin of the emission. Several X-ray emission lines are clearly visible in the CCD spectra, including the high-temperature Fe K-alpha complex. The emission can be accurately modeled as a multi-temperature thermal plasma with cool (kT < 1 keV) and hot (kT > 3 keV) components. The presence of a hot component is compelling evidence that the X-rays originate in magnetically confined plasma, either in the Herbig star itself or in the corona of an as yet unseen late…
We present Chandra-HETGS observations of the Herbig Ae star HD 104237 and the associated young stars comprising lower mass stars, in the 0.15-1.75\msol mass range, in their pre-main sequence phase. The brightest X-ray source in the association is the central system harboring the Herbig Ae primary, and a K3 companion. Its X-ray variability indicates modulation possibly on time scales of the rotation period of the Herbig Ae star, and this would imply that the primary significantly contributes to the overall emission. The spectrum of the Herbig Ae+K3 system shows a soft component significantly mo…
New AAT near-infrared and SEST 12CO J=2-1 observations are combined with existing ISO mid-infrared and ATCA cm radio continuum observations to examine the protostellar content of the Bok globule BHR 71. Together with observations of Herbig-Haro objects, these data show: (1) Two protostellar sources, IRS1 and IRS2, with a separation of ~17 arcsec (3400 AU) are located within BHR 71. (2) Each protostar is driving its own molecular outflow. The outflow from IRS1 is much larger in extent, is more massive, and dominates the CO emission. (3) Both protostars are associated with Herbig-Haro objects an…
We report on results of near-infrared and optical observations of the mm disk embedded in the Bok globule CB 26 (Launhardt & Sargent 2001). The near-infrared images show a bipolar reflection nebula with a central extinction lane which coincides with the mm disk. Imaging polarimetry of this object yielded a polarization pattern which is typical for a young stellar object surrounded by a large circumstellar disk and an envelope, seen almost edge-on. The strong linear polarization in the bipolar lobes is caused by single scattering at dust grains and allowed to locate the illuminating source whic…
We present high sensitivity 12CO and 13CO (1-0) molecular line maps covering the full extent of the parsec scale Haro~6-10 Herbig-Haro (HH) flow. We report the discovery of a molecular CO outflow along the axis of parsec-scale HH flow. Previous molecular studies missed the identification of the outflow probably due to their smaller mapping area and the confusing spectral features present towards the object. Our detailed molecular line study of the full 1.6 pc extent of the optical flow shows evidence for both blueshifted and redshifted gas set in motion by Haro~6-10 activity. The molecular out…
We present linear spectropolarimetric data for eight Herbig Be and four Herbig Ae stars at H alpha, H beta and H gamma. Changes in the linear polarisation are detected across all Balmer lines for a large fraction of the observed objects, confirming that the small-scale regions surrounding these objects are flattened (i.e. disk-like). Furthermore, all objects with detections show similar characteristics at the three spectral lines, despite differences in transition probability and optical depth going from H alpha to H gamma. A large fraction of early Herbig Be stars (B0-B3) observed show line d…
Adaptive optics imaging of the bright visual T Tauri binary AS 353 with the Subaru Telescope shows that it is a hierarchical triple system. The secondary component, located 5.6" south of AS 353A, is resolved into a subarcsecond binary, AS 353Ba and Bb, separated by 0.24". Resolved spectroscopy of the two close components shows that both have nearly identical spectral types of about M1.5. Whereas AS 353A and Ba show clear evidence for an infrared excess, AS 353Bb does not. We discuss the possible role of multiplicity in launching the large Herbig-Haro flow associated with AS 353A.
Using UBVRI Halpha CCD photometric observations and the archival NIR and X-ray data, we have carried out a multi-wavelength study of a young star cluster NGC 7419. An age of 22.5+/-3.0 Myr and a distance of 3230^{+330}_{-430} pc are derived for the cluster with a higher value of color excess ratio E(U-B)/E(B-V) than the normal one. There is an evidence for mass segregation in this dynamically relaxed cluster with mass function slope is in agreement with the Salpeter value. NIR and Halpha excess support the existence of a young (< 2 Myr) stellar population of Herbig Ae/Be stars (> 3.0 M_sun) in…
Chandra X-ray imaging spectroscopy of the nearby Herbig Ae star HD 163296 at 100 AU angular resolution is reported. A point-like, soft (kT~0.5 keV), emission-line source is detected at the location of the star with an X-ray luminosity of 4.0e29 erg/s. In addition, faint emission along the direction of a previously-detected Ly-alpha-emitting jet and Herbig-Haro outflow may be present. The relatively low luminosity, lack of a hard spectral component, and absence of strong X-ray variability in HD 163296 can be explained as originating from optically-thin shock-heated gas accreting onto the stella…
We present a statistical study of the X-Ray emission toward 22 Herbig AeBe stars using the Chandra archive. We probe the origin of the X-Rays toward Herbig stars: are they intrinsic? This question is addressed by correlations between the physical stellar properties and the X-Ray emission. There is a weak correlation between the continuum radio emission at lambda = 3.6cm and Lx, which suggests that the X-Ray emission depends upon the source. On the other hand, no correlation was found with the stellar rotational period, but that only excludes solar-like magnetic activity as the origin of the X-…
We present Submillimeter Array observations of the Herbig Ae star HD169142 in 1.3 millimeter continuum emission and 12CO J=2-1 line emission at 1.5 arcsecond resolution that reveal a circumstellar disk. The continuum emission is centered on the star position and resolved, and provides a mass estimate of about 0.02 solar masses for the disk. The CO images show patterns in position and velocity that are well matched by a disk in Keplerian rotation with low inclination to the line-of-sight. We use radiative transfer calculations based on a flared, passive disk model to constrain the disk paramete…
The results of spectroscopic study of Ae Herbig star RR Tau are reported. The observations were carried out with a moderate resolution. In accordance with the presented data the Halpha line exhibits a double-peaked emission profile. The blue component is weaker than or equal to the red one. Variations of the Halpha equivalent width by a factor of 4 - 5 were found. The structure of this line also varies. On JD 2447148 a red absorption reversal of the Halpha profile was observed. The Hbeta spectral line exhibited both emission and absorption. On JD 2449664 the single-peak emission shifted to the…
We present new results on the nature of the Herbig-Haro-like object 73 (HHL73, also known as [G84b] 11) based on narrow-band CCD H_alpha and [SII] images of the HHL73 field, and Integral Field Spectroscopy and radio continuum observations at 3.6 cm covering the emission of the HHL 73 object. The CCD images allow us to resolve the HHL 73 comet-shaped morphology into two components and a collimated emission feature of ~4" long, reminiscent of a microjet. The IFS spectra of HHL 73 showed emission lines characteristic of the spectra of Herbig--Haro objects. The kinematics derived for HHL~73 are co…
Aims. The chemistry of, and infrared (IR) emission from, polycyclic aromatic hydrocarbons (PAHs) in disks around Herbig Ae/Be and T Tauri stars are investigated. The equilibrium distribution of the PAHs over all accessible charge/hydrogenation states depends on the size and shape of the PAHs and on the physical properties of the star and surrounding disk. Methods. A chemistry model is created to calculate this equilibrium distribution. Destruction of PAHs by ultraviolet (UV) photons, possibly in multi-photon absorption events, is taken into account. The chemistry model is coupled to a radiativ…
We performed a systematic search for Chandra archival observations of Herbig Ae/Be stars. These stars are fully radiative and not expected to support dynamo action analogous to their convective lower-mass counterparts, the T Tauri stars. Their X-ray emission has remained unexplained. The superior spatial resolution of Chandra with respect to previous X-ray instrumentation has allowed us to examine the possible role of late-type companions in generating the observed X-rays. In the total sample of 17 Herbig Ae/Be stars, 8 are resolved from X-ray emitting faint companions or other unrelated X-ray…
Recently X-ray emission from protostellar jets has been detected with both XMM-Newton and Chandra satellites, but the physical mechanism which can give rise to this emission is still unclear. We performed an extensive exploration of a wide space of the main parameters influencing the jet/ambient interaction. Aims include: 1) to constrain the jet/ambient interaction regimes leading to the X-ray emission observed in Herbig-Haro objects in terms of the emission by a shock forming at the interaction front between a continuous supersonic jet and the surrounding medium; 2) to derive detailed predict…
A survey for candidate Herbig-Haro objects was performed to search for evidence of star formation in Galactic dark clouds. For this aim true colour images were created from blue, red, and infrared DSS2 plates and inspected. Follow-up I-band, Halpha, and [SII] CCD imaging and long-slit spectroscopy using the Tautenburg 2-m telescope was carried out to verify candidate objects. In the case of LDN 1415, the presence of a Herbig-Haro flow could be revealed which is henceforth named HH 892. In addition, an arcuate nebula was found which is barely seen on the DSS2 infrared plate (epoch 1996) and not…
VLBA observations of water masers toward the region of NGC1333 near SVS13, the driving source for the well-known Herbig-Haro objects HH7-11, are reported. Maser emission was observed over four epochs spaced by three weeks during late 1998. SVS13 is associated with the millimeter continuum SED Class I source SSV13A1. High resolution CO observations have secured the association of the flow with the continuum object on arc-second scales. A 1998 Aug 12 VLA observation places the blueshifted masers within 80 AU (0''.2) of the 2.7 mm position for A1 reported from BIMA. We report observations of two …
A general theoretical framework is developed for interpreting spectropolarimetric observations of optically thin emission line scattering from small dust particles. Spatially integrated and spatially resolved line profiles of both scattered intensity and polarization are calculated analytically from a variety of simple kinematic models. These calculations will provide a foundation for further studies of emission line scattering from dust and electrons in such diverse astrophysical environments as Herbig-Haro objects, symbiotic stars, starburst galaxies and active galactic nuclei.
We present 2.0-2.4micron integral field spectroscopy at adaptive optics spatial resolution (~0.''1) obtained with the Near-infrared Integral Field Spectrograph (NIFS) at Gemini North Observatory of six Classical T Tauri stars: T Tau, DG Tau, XZ Tau, HL Tau, RW Aur and HV Tau C. In all cases, the v=1-0 S(1) (2.12 micron) emission is detected at spatially extended distances from the central stars. The bulk of the H_2 emission is typically not spatially coincident with the location of continuum flux. Multiple transitions detected in the K-band spectra show that H_2 level populations are typical o…
