Local Standard Of Rest Velocity Research Articles

East Asian VLBI Network astrometry toward the extreme outer Galaxy: Kinematic distance with the proper motion of G034.84−00.95

Abstract We aim to reveal the structure and kinematics of the Outer Scutum–Centaurus (OSC) arm located on the far side of the Milky Way through very long baseline interferometry (VLBI) astrometry using KaVA, which is composed of KVN (the Korean VLBI Network) and VERA (VLBI Exploration of Radio Astrometry). We report the proper motion of a 22 GHz H2O maser source, which is associated with the star-forming region G034.84−00.95, to be (μαcos δ, μδ) = (−1.61 ± 0.18, −4.29 ± 0.16) mas yr−1 in equatorial coordinates (J2000.0). We estimate the 2D kinematic distance to the source to be 18.6 ± 1.0 kpc, which is derived from the variance weighted average of kinematic distances with local standard of rest velocity and the galactic-longitude component of the measured proper motion. Our result places the source in the OSC arm and implies that G034.84−00.95 is moving away from the Galactic plane with a vertical velocity of −38 ± 16 km s−1. Since the H i supershell GS033+06−49 is located at a kinematic distance roughly equal to that of G034.84−00.95, it is expected that gas circulation occurs between the outer Galactic disk around G034.84−00.95 with a Galactocentric distance of $12.8^{+1.0}_{-0.9}\:$kpc and the halo. We evaluate possible origins of the fast vertical motion of G034.84−00.95, which are (1) supernova explosions and (2) cloud collisions with the Galactic disk. However, neither of these possibilities are matched with the results of VLBI astrometry or the spatial distributions of H ii regions and H i gas.

Dents in the Veil: protostellar feedback in Orion

Context. Interest in stellar feedback has recently increased because new studies suggest that radiative and mechanical feedback from young massive stars significantly regulates the physical and chemical composition of the interstellar medium. Recent SOFIA [C ii] 158 μm observations of the Orion Veil have revealed that the expanding bubble is powered by stellar winds and influenced by previously active molecular outflows of ionizing massive stars. Aims. We aim to investigate the mechanical feedback on the whole Veil shell by searching for jets and outflows that interact with the Veil shell and by determining the driving mechanisms of these collisions. Methods. We make use of the [C ii] 158 μm map of the Orion Nebula taken with the upGREAT instrument on board SOFIA. We image the [C ii] emission of more extreme local standard of rest velocities (υLSR) between −3 and −20 km s−1 to pinpoint the high-velocity structures. Using position-velocity (PV) diagrams and high-velocity [C ii] emission, we search for spots of shock-accelerated [C ii]-emitting gas, so called dents. At these positions, we extract [C ii] line profiles to identify velocity components. We also compare the intensity distribution of the [C ii] emission with that of 8 μm PAH and 70 μm warm dust emission to see if there is a trend among these PDR tracers and to understand the origin of the dents. Results. We identify six dents on the Veil shell, with sizes between 0.3 and 1.35 pc and expansion velocities ranging from 4 to 14 km s−1, relative to the expanding Veil shell. The [C ii] line widths toward the dents vary from 4 to 16 km s−1 indicating that the dents are the result of interaction of the highly turbulent motions (e.g., shocked gas) with the Veil shell. Moreover, dents appear only in the [C ii] PV diagram, not in the 12CO or HI 21 cm diagrams. Furthermore, the intensity distribution of the [C ii] emission of the dents has a tight correlation with that of the 8 and 70 μm as long as the Orion Molecular Cloud or the Veil do not dominate its emission. Also, the observed dents do not have CO counterpart emission. These results indicate that the dents are made up of CO-dark H2 gas. In light of these findings, as well as the momenta of the dents and their dynamical timescales, we propose that the dents are created by the interaction of collimated jets and outflows from protostars in the Orion star-forming cloud with luminosities ranging from 103 to 104 L⊙, which indicates that they are B-type stars, with the surrounding Veil shell. However, it is challenging to pinpoint the driving stars as they may have moved from the original ejection points of the jets and outflows. Conclusions. We conclude that the dynamics of the expanding Veil shell is influenced not just by the O-type stars in the Trapezium cluster, but also by less massive stars, especially B-type stars, in the Orion Nebula. Mechanical feedback from protostars with a range of masses appears to play an important role in determining the morphology of H II regions and injecting turbulence into the medium.

The First Mid-infrared Detection of HNC in the Interstellar Medium: Probing the Extreme Environment toward the Orion Hot Core

Abstract We present the first mid-infrared (MIR) detections of HNC and in the interstellar medium, and numerous resolved HCN rovibrational transitions. Our observations span 12.8–22.9 μm toward the hot core Orion IRc2, obtained with the Echelon-Cross-Echelle Spectrograph aboard the Stratospheric Observatory for Infrared Astronomy (SOFIA). In particular, ∼5 km s−1 resolution distinguishes individual rovibrational transitions of the HNC and HCN P, Q, and R branches; and the R branch. This allows direct measurement of the species’ excitation temperatures, column densities, and relative abundances. HNC and exhibit a local standard of rest velocity of −7 km s−1 that may be associated with an outflow from nearby radio source I and an excitation temperature of about 100 K. We resolve two velocity components for HCN, the primary component also being at −7 km s−1 with a temperature of 165 K. The hottest component, which had never before been observed, is at 1 km s−1 with a temperature of 309 K. This is the closest component to the hot core’s center measured to date. The derived is below expectation for Orion’s Galactocentric distance, but the derived HCN/HNC = 72 ± 7 is expected for this extreme environment. Compared to previous sub-millimeter and millimeter observations, our SOFIA line survey of this region shows that the resolved MIR molecular transitions are probing a distinct physical component and isolating the chemistry closest to the hot core.

Revisiting the Distance, Environment, and Supernova Properties of SNR G57.2+0.8 that Hosts SGR 1935+2154

Abstract We have performed a multiwavelength study of supernova remnant (SNR) G57.2+0.8 and its environment. The SNR hosts the magnetar SGR 1935+2154, which emitted an extremely bright millisecond-duration radio burst on 2020 April 28. We used the 12CO and 13CO J = 1–0 data from the Milky Way Image Scroll Painting CO line survey to search for molecular gas associated with G57.2+0.8, in order to constrain the physical parameters (e.g., the distance) of the SNR and its magnetar. We report that SNR G57.2+0.8 is likely impacting the molecular clouds (MCs) at the local standard of rest (LSR) velocity and excites a weak 1720 MHz OH maser with a peak flux density of 47 mJy beam−1. The chance coincidence of a random OH spot falling in the SNR is ≤12%, and the OH–CO correspondence chance is 7% at the maser spot. This combines to give <1% false probability of the OH maser, suggesting a real maser detection. The LSR velocity of the MCs places the SNR and magnetar at a kinematic distance of 6.6 ± 0.7 kpc. The nondetection of thermal X-ray emission from the SNR and the relatively dense environment suggests G57.2+0.8 be an evolved SNR with an age . The explosion energy of G57.2+0.8 is lower than , which is not very energetic even assuming a high ambient density . This reinforces the opinion that magnetars do not necessarily result from very energetic supernova explosions.

Molecular globules in the Veil bubble of Orion

Strong winds and ultraviolet (UV) radiation from O-type stars disrupt and ionize their molecular core birthplaces, sweeping up material into parsec-size shells. Owing to dissociation by starlight, the thinnest shells are expected to host low molecular abundances and therefore little star formation. Here, we expand previous maps made with observations using the IRAM 30 m telescope (at 11″ ≃ 4500 AU resolution) and present square-degree12CO and13CO (J= 2–1) maps of the wind-driven “Veil bubble” that surrounds the Trapezium cluster and its natal Orion molecular core (OMC). Although widespread and extended CO emission is largely absent from the Veil, we show that several CO “globules” exist that are blueshifted in velocity with respect to OMC and are embedded in the [C II] 158μm-bright shell that confines the bubble. This includes the first detection of quiescent CO at negative local standard of rest velocities in Orion. Given the harsh UV irradiation conditions in this translucent material, the detection of CO globules is surprising. These globules are small (Rg= 7100 AU), not massive (Mg= 0.3M⊙), and are moderately dense:nH= 4 × 104cm−3(median values). They are confined by the external pressure of the shell,Pext∕k≳ 107cm−3K, and are likely magnetically supported. They are either transient objects formed by instabilities or have detached from pre-existing molecular structures, sculpted by the passing shock associated with the expanding shell and by UV radiation from the Trapezium. Some represent the first stages in the formation of small pillars, others of isolated small globules. Although their masses (Mg<MJeans) do not suggest they will form stars, one globule matches the position of a known young stellar object. The lack of extended CO in the “Veil shell” demonstrates that feedback from massive stars expels, agitates, and reprocesses most of the disrupted molecular cloud gas, thereby limiting the star-formation rate in the region. The presence of molecular globules is a result of this feedback.

Astrometry of H2O masers in the W 48 A (G35.20−01.74) H ii region with VERA: A compact disk outflow inside core H-2a

Abstract W 48 A core H-2a is one of the young massive protostellar objects in the W 48 region. We conducted multi-epoch astrometric observations of the water (H2O) masers associated with the W 48 A core H-2a with VLBI Exploration of Radio Astrometry (VERA). The trigonometric annual parallax of W 48 A core H-2a was measured to be 0.433 ± 0.026 mas, corresponding to a distance of $2.31^{+0.15}_{-0.13}$ kpc. This agrees with the revised parallax of 0.412 ± 0.014 mas by Wu et al. (2019, ApJ, 874, 94). We obtained the systemic proper motion and local standard of rest velocity to be (μαcos δ, μδ) = (0.26 ± 0.73, −3.87 ± 0.33) mas yr−1 and vLSR = 41.9 ± 0.9 km s−1, respectively. The distribution of the H2O masers covers an area of 70 mas × 80 mas, corresponding to 160 au × 180 au at the distance of 2.31 kpc. The internal proper motions of the H2O masers trace an east–west bipolar outflow. With the recent absolute position measurement of the 6.7 GHz methanol (CH3OH) masers and their elliptical distribution, whose major axis is perpendicular to the axis of the bipolar outflow, we suggest the presence of a disk outflow system in core H-2a. The spectral energy distribution (SED) of the driving source of core H-2a was previously reported to yield a luminosity and envelope mass of 8000 ± 1000 $W_{\odot}$ and 170 ± 30 $M_{\odot}$, respectively. Refitting the SED with the new distance, we obtained the luminosity to be 3100 ± 388 $L_{\odot}$ and derived the zero age main sequence (ZAMS) stellar mass to be 9 ± 1 $M_{\odot}$. Using our distance measurement, we derived the peculiar motion of W 48 A to be (Us, Vs, Ws) = (1 ± 4, 5 ± 6, −15 ± 5) km s−1.

A Small-scale Investigation of Molecular Emission toward the Tip of the Western Lobe of W50/SS 433

Abstract We perform a molecular (CO and CN) line observation using the IRAM 30 m telescope toward two small regions near the western edge of supernova remnant (SNR) W50/SS 433. CO observation reveals spatial correspondence of two molecular clumps at the local-standard-of-rest (LSR) velocity around +53 , with multiwavelength local features of the W50/SS 433 system. One of the two clumps appears to be embedded in a void of diffuse radio and X-ray emission. Toward the two clumps, asymmetric broad-line profiles of the 12CO lines are obtained, which provide kinematic evidence of the association between the clumps and the jet-related gas. The 12CO J = 2–1/J = 1–0 line ratios (≳0.9) and the kinetic temperatures (∼30 K) of the clumps are distinctively higher than all those of the clumps at other LSR velocities along the same line of sight, which may be physical signatures of the association. We show that the clump coincident with the void can survive the thermal heating if it is surrounded by hot gas, with an evaporation timescale much larger than the age of SNR W50. We also show that the thermal equilibrium in the high-temperature clumps can be maintained by the heating of the penetrating environmental cosmic rays. CN (J = 3/1–1/2) line emission is detected in the two clumps, and the CN abundances derived are much higher than that in the interstellar molecular clouds (MCs) and that in the SNR-interacting MCs.

The environment of supernova remnant VRO 42.05.01 as probed with IRAM 30m molecular line observations

Context. The environment of supernova remnants (SNRs) is a key factor in their evolution, particularly at later stages of their existence. Mixed-morphology (MM) SNRs have a peculiar centre-filled X-ray shape that remains enigmatic. It is often assumed that they evolve in very dense environments, and that the X-ray morphology is due to interactions between the SNRs and their surroundings. Aims. We aim to determine whether VRO 42.05.01 is embedded in, and interacting with, a dense molecular environment. We also aim to understand the multi-wavelength emission from the environment of this SNR, and whether the interstellar material can be responsible for the the MM nature of the source, and for its strange radio and optical shape. Methods. We used the IRAM telescope in Pico Veleta, Spain, to search for signs of interaction between the SNR and neighbouring molecular clouds. We observed a region of 26′ × 14′ towards the west of VRO 42.05.01 and a region of 8′ × 4′ towards the north of the remnant in the 12CO J = 1−0, 13CO J = 1−0, and 12CO J = 2−1 transitions with the EMIR receiver. We made maps of the properties of the observed molecular clouds (peak temperatures, central velocities, velocity dispersions), as well as maps of column density along the line of sight, and ratio of the 12CO J = 2−1 to 12CO J = 1−0 transitions. We also analyse archival optical, infrared, and radio spectroscopic data for other hints on the nature of the medium. Results. We do not find conclusive physical proof that the SNR is interacting with the few, clumpy molecular clouds that surround it in the region of our observations, although there is some suggestion of such interaction (in a region outside our map) from infrared emission. We find that there is a velocity gradient in one of the molecular clouds that is consistent with a stellar wind blown by a 12−14 M⊙ progenitor star. We reassess the literature distance to VRO 42.05.01, and propose that it has a local standard of rest velocity of − 6 km s−1, and that it is located 1.0 ± 0.4 kpc away (the earlier distance value was 4.5 ± 1.5 kpc). We find that a dust sheet intersects VRO 42.05.01 and is possibly related to its double shell-shaped morphology.

A 6.7 GHz Methanol Maser Survey. II. Low Galactic Latitudes

Abstract We report the results of our systematic survey for Galactic 6.7 GHz Class II CH3OH maser emission toward a sample of young stellar objects. The survey was conducted with the Shanghai Tianma Radio Telescope (TMRT). The sample consists of 3348 sources selected from the all-sky Wide-field Infrared Survey Explorer (WISE) point-source catalog. We discussed the selection criteria in detail and the detection results of those at high Galactic latitudes (i.e., ) in a previous paper (Yang et al. 2017). Here, we present the results from the survey of those at low Galactic latitudes, i.e., . Of 1875 selected WISE point sources, 291 positions that were actually associated with 224 sources that were detected with CH3OH maser emission. Among them, 32 are newly detected. A majority of the newly detected sources are associated with bright WISE sources. The majority of the detected sources (209/224 = 93.3%) are quite close to the Galactic Plane ( ) and lie on the inner spiral arms with positive local standard of rest velocities. The detection rate and the color–color distribution of our detection are all matched with our anticipation. Combining with detections from previous surveys, we compile a catalog of 1085 sources with 6.7 GHz CH3OH maser emission in our Galaxy.

Constraining the Solar Galactic Reflex Velocity using Gaia Observations of the Sagittarius Stream

Abstract Because of its particular orientation around the Galaxy—i.e., in a plane nearly perpendicular to the Galactic plane and containing both the Sun and Galactic center—the Sagittarius (Sgr) stream provides a powerful means by which to measure the solar reflex velocity, and thereby infer the velocity of the Local Standard of Rest (LSR), in a way that is independent of assumptions about the solar Galactocentric distance. Moreover, the solar reflex velocity with respect to the stream is projected almost entirely into the proper motion component of Sgr stream stars perpendicular to the Sgr plane, which makes the inferred velocity relatively immune to most Sgr model assumptions. Using Gaia Data Release 2 proper motions of ∼2000 stars identified to be Sgr stream candidates in concert with the Law & Majewski Sgr N-body models (which provide a good match to the Gaia observations), we constrain the solar reflex velocity induced by its orbital motion around the Galaxy to be Θ⊙ = 253 ± 6 km s−1. Assuming a solar peculiar motion in the direction of orbital rotation of 12 km s−1, and an LSR velocity of 12 km s−1 with respect to the local circular speed, the implied circular speed of the Milky Way at the solar circle is 229 ± 6 km s−1.

Blowing in the Milky Way Wind: Neutral Hydrogen Clouds Tracing the Galactic Nuclear Outflow

Abstract We present the results of a new sensitive survey of neutral hydrogen above and below the Galactic Center with the Green Bank Telescope. The observations extend up to Galactic latitude with an effective angular resolution of 9.′5 and an average rms brightness temperature noise of 40 mK in a 1 channel. The survey reveals the existence of a population of anomalous high-velocity clouds extending up to heights of about 1.5 kpc from the Galactic plane and showing no signature of Galactic rotation. These clouds have local standard of rest velocities , and assuming a Galactic Center origin, they have sizes of a few tens of parsec and neutral hydrogen masses spanning . Accounting for selection effects, the cloud population is symmetric in longitude, latitude, and V LSR. We model the cloud kinematics in terms of an outflow expanding from the Galactic Center and find the population consistent with being material moving with radial velocity distributed throughout a bicone with opening angle . This simple model implies an outflow luminosity erg s−1 over the past 10 Myr, consistent with star formation feedback in the inner region of the Milky Way, with a cold gas mass-loss rate . These clouds may represent the cold gas component accelerated in the nuclear wind driven by our Galaxy, although some of the derived properties challenge current theoretical models of the entrainment process.

Galactic Hα emission line studies using DEFPOS at the TÜBİTAK National Observatory

H$\alpha $ spectral line (6563 Å) profiles of eight northern H II regions in our galaxy (Sh2-25, Sh2-131, Sh2-237, IC 434, IC 1318, NGC 1982, NGC 6543, and NGC 6611) have been obtained using the Dual Etalon Fabry-Pérot Optical spectrometer (DEFPOS) with a 4' field of view, located at the coudé focus of the 150 cm RTT150 telescope at the TÜBİTAK National Observatory (TUG, Antalya, Turkey). Observations were carried out during the nights of 25-27 December 2015 and 6-7 June 2017 with different long exposure times ranging from 900 s to 3600 s. These spectra provide information about the local standard of rest (LSR) velocities, the full width at half maximum (FWHM), and densities of the sources. The LSR velocities and the FWHM of the H$\alpha $ emission lines were found to be in the range of -50.31 km/s to 27.57 km/s and 34.88 km/s to 44.54 km/s (mean FWHM: 37.19 km/s), respectively. The NGC 6543 (Cat's Eye Nebula) is the faintest one (75.06 R), while the NGC 1982 H II region is brightest source (38,477.3 R). The LSR velocity and the FWHM results of the DEFPOS/RTT150 system were compared with the data by several authors given in the literature and the results of DEFPOS data were found to be in good agreement with data given in the literature. Since there is not enough information on LSR velocities and intensities of such galactic sources with low angular size in the literature, we believe that this spectrometer will provide a powerful tool for the study of diffuse ionized gas and these new results may have significant contributions to the literature. In the future, we are planning to prepare H$\alpha $ maps with the 4' field of view of some diffuse ionized emission sources selected from VTSS and WHAM H$\alpha $ maps with large fields of view.

SiS in the Circumstellar Envelope of IRC +10216: Maser and Quasi-thermal Emission

Abstract We present new Effelsberg 100-m, Australia Telescope Compact Array (ATCA), and Very Large Array observations of rotational SiS transitions in the circumstellar envelope (CSE) of IRC +10216. Thanks to the high angular resolution achieved by the ATCA observations, we unambiguously confirm that the molecule’s transition exhibits maser action in this CSE, as first suggested more than 30 years ago. The maser emission’s radial velocity, peaking at a local standard of rest velocity of −39.862 ± 0.065 km s−1, indicates that it arises from an almost fully accelerated shell. Monitoring observations show time variability of the SiS ( ) maser. The two lowest-J SiS quasi-thermal emission lines trace a much more extended emitting region than previous high-J SiS observations. Their distributions show that the SiS quasi-thermal emission consists of two components: one is very compact ( , corresponding to cm), and the other extends out to a radius >11″. An incomplete shell-like structure is found in the northeast, which is indicative of existing SiS shells. Clumpy structures are also revealed in this CSE. The gain of the SiS ( ) maser (optical depths of about −5 at the blueshifted side and, assuming inversion throughout the entire line’s velocity range, about −2 at the redshifted side) suggests that it is unsaturated. The SiS ( ) maser can be explained in terms of ro-vibrational excitation caused by infrared pumping, and we propose that infrared continuum emission is the main pumping source.

MULTI-WAVELENGTH STUDY OF THE SUPERNOVA REMNANT KES 79 (G33.6+0.1): ON ITS SUPERNOVA PROPERTIES AND EXPANSION INTO A MOLECULAR ENVIRONMENT

ABSTRACT Kes 79 (G33.6+0.1) is an aspherical thermal composite supernova remnant (SNR) observed across the electromagnetic spectrum and showing an unusual highly structured morphology, in addition to harboring a central compact object (CCO). Using the CO J = 1–0, J = 2–1, and J = 3–2 data, we provide the first direct evidence and new morphological evidence to support the physical interaction between the SNR and the molecular cloud in the local standard of rest velocity . We revisit the 380 ks XMM-Newton observations and perform a dedicated spatially resolved X-ray spectroscopic study with careful background subtraction. The overall X-ray-emitting gas is characterized by an under-ionized ( ) cool ( keV) plasma with solar abundances, plus an under-ionized ( ) hot ( keV) plasma with elevated Ne, Mg, Si, S, and Ar abundances. The X-ray filaments, spatially correlated with the 24 IR filaments, are suggested to be due to the SNR shock interaction with dense gas, while the halo forms from SNR breaking out into a tenuous medium. Kes 79 appears to have a double-hemisphere morphology viewed along the symmetric axis. Projection effect can explain the multiple-shell structures and the thermal composite morphology. The high-velocity, hot ( keV) ejecta patch with high metal abundances, together with the non-uniform metal distribution across the SNR, indicate an asymmetric SN explosion of Kes 79. We refine the Sedov age to 4.4–6.7 kyr and the mean shock velocity to 730 . Our multi-wavelength study suggests a progenitor mass of ∼15–20 solar masses for the core-collapse explosion that formed Kes 79 and its CCO, PSR J1852+0040.

EXPANDING MOLECULAR BUBBLE SURROUNDING TYCHO’S SUPERNOVA REMNANT (SN 1572) OBSERVED WITH THE IRAM 30 m TELESCOPE: EVIDENCE FOR A SINGLE-DEGENERATE PROGENITOR

ABSTRACT Whether the progenitors of SNe Ia are single-degenerate or double-degenerate white dwarf (WD) systems is a highly debated topic. To address the origin of Tycho’s Type Ia supernova remnant (SNR), SN 1572, we have carried out a 12CO J = 2–1 mapping and a 3 mm line survey toward the remnant using the IRAM 30 m telescope. We show that Tycho is surrounded by a clumpy molecular bubble at a local standard of rest velocity of , which expands at a speed of and has a mass of (at the distance of 2.5 kpc). Enhanced 12CO J = 2–1 line emission relative to 12CO J = 1–0 emission and possible line broadenings (in velocity range −64 to −60 km s−1) are found at the northeastern boundary of the SNR, where the shell is deformed and decelerated. These features, combined with the morphological correspondence between the expanding molecular bubble and Tycho, suggest that the SNR is associated with the bubble at the velocity range −66 to −57 km s−1. The most plausible origin for the expanding bubble is the fast outflow (with velocity of hundreds km s−1) driven from the vicinity of a WD as it accreted matter from a nondegenerate companion star. The SNR has been expanding in the low-density wind-blown bubble, and the shock wave has just reached the molecular cavity wall. This is the first unambiguous detection of an expanding bubble driven by the progenitor of a Type Ia SNR, which constitutes evidence for a single-degenerate progenitor for this SN Ia.

THE METAL-ENRICHED THERMAL COMPOSITE SUPERNOVA REMNANT KESTEVEN 41 (G337.8-0.1) IN A MOLECULAR ENVIRONMENT

The physical nature of thermal composite supernova remnants (SNRs) remains controversial. We have revisited the archival XMM-Newton and Chandra data of the thermal composite SNR Kesteven 41 (Kes 41 or G337.8-0.1) and performed a millimeter observation toward this source in the $^{12}$CO, $^{13}$CO, and C$^{18}$O lines. The X-ray emission, mainly concentrated toward the southwestern part of the SNR, is characterized by distinct S and Ar He-like lines in the spectra. The X-ray spectra can be fitted with an absorbed nonequilibrium ionization collisional plasma model at a temperature of 1.3-2.6 keV and an ionization timescale of 0.1-1.2$\times$10$^{12}$ cm$^{-3}$ s. The metal species S and Ar are overabundant, with 1.2-2.7 and 1.3-3.8 solar abundances, respectively, which strongly indicate the presence of a substantial ejecta component in the X-ray-emitting plasma of this SNR. Kes 41 is found to be associated with a giant molecular cloud (MC) at a systemic local standard of rest velocity of -50 km s$^{-1}$ and confined in a cavity delineated by a northern molecular shell, a western concave MC that features a discernible shell, and an HI cloud seen toward the southeast of the SNR. The birth of the SNR in a preexisting molecular cavity implies a mass of $\gtrsim$18 M$_{\odot}$ for the progenitor if it was not in a binary system. Thermal conduction and cloudlet evaporation seem to be feasible mechanisms to interpret the X-ray thermal composite morphology, and the scenario of gas reheating by the shock reflected from the cavity wall is quantitatively consistent with the observations. An updated list of thermal composite SNRs is also presented in this paper.

DEFPOS Hα observations of the W80 Complex

We present Hα emission line measurements of the W80 nebula complex. A total of 26 regions have been observed inside the nebula with the Dual Etalon Fabry-Perot Optical Spectrometer system at the f/48 Coudé focus of the 150 cm RTT150 telescope located at TUBITAK National Observatory in Antalya, Turkey. The intensities, local standard of rest velocities, heliocentric radial velocities and linewidths for full width at half maximum of the Hα emission lines have been determined from these observations. They lie in the range of 259 to 1159 Rayleigh (R; 1R = 106/4π photons cm−2 sr−1 s−1 = 2.41 × 10−7 erg cm−2 sr−1 s−1 at Hα), 4 to 12 km s−1, −3 to −11 km s−1 and 44 to 55 km s−1, respectively. The radial velocity measurements show that there are several maxima and minima inside W80. The new results confirm findings in the literature that the complex seems to be rather uniform in terms of radial velocity and no turbulent motion is seen inside the complex. The average value of the calculated emission measure for the region is 3.1 pc cm−6.

MOLECULAR ENVIRONMENT AND AN X-RAY SPECTROSCOPY OF SUPERNOVA REMNANT KESTEVEN 78

We investigate the molecular environment of the Galactic supernova remnant (SNR) Kesteven 78 and perform an XMM-Newton X-ray spectroscopic study for the northeastern edge of the remnant. SNR Kes78 is found to interact with the molecular clouds (MCs) at a systemic local standard of rest velocity of 81km/s. At around this velocity, the SNR appears to contact a long molecular strip in the northeast and a large cloud in the east as revealed in the 13CO line, which may be responsible for the radio brightness peak and the OH maser, respectively. The 12CO-line bright region morphologically matches the eastern bright radio shell in general, and the SNR is consistent in extent with a CO cavity. Broadened 12CO line profiles discerned in the eastern maser region and the western clumpy molecular arc and the elevated 12CO J=2-1/J=1-0 ratios along the SNR boundary may be signatures of shock perturbation in the molecular gas. The SNR-MC association places the SNR at a kinematic distance of 4.8 kpc. The X-rays arising from the northeastern radio shell are emitted by underionized hot (~1.5 keV), low-density (~0.1 cm^{-3}) plasma with solar abundance, and the plasma may be of intercloud origin. The age of the remnant is inferred to be about 6 kyr. The size of the molecular cavity in Kes78 implies an initial mass around 22Msun for the progenitor.

HERSCHEL /HIFI OBSERVATIONS OF HYDROGEN FLUORIDE TOWARD SAGITTARIUS B2(M)

Herschel/HIFI observations have revealed the presence of widespread absorption by hydrogen fluoride (HF) J = 1-0 rotational transition, toward a number of Galactic sources. We present observations of HF J = 1-0 toward the high-mass star-forming region Sagittarius B2(M). The spectrum obtained shows a complex pattern of absorption, with numerous features covering a wide range of local standard of rest velocities (-130 to 100 km -1). An analysis of this absorption yields HF abundances relative to H2 of ~1.3 {\times}10-8, in most velocity intervals. This result is in good agreement with estimates from chemical models, which predict that HF should be the main reservoir of gas-phase fluorine under a wide variety of interstellar conditions. Interestingly, we also find velocity intervals in which the HF spectrum shows strong absorption features that are not present, or are very weak, in spectra of other molecules, such as 13CO (1-0) and CS (2-1). HF absorption reveals components of diffuse clouds with small extinction that can be studied for the first time. Another interesting observation is that water is significantly more abundant than hydrogen fluoride over a wide range of velocities toward Sagittarius B2(M), in contrast to the remarkably constant H2O/HF abundance ratio with average value close to unity measured toward other Galactic sources.

DEFPOS H α observations of H ii regions

We present H α emission line measurements of northern bright H ii regions selected from the Sharpless (1959) catalog near the Galactic plane ( b ⩽ ± 6°). A total of 10 H ii regions were observed with DEFPOS (Dual Etalon Fabry–Perot Optical Spectrometer) system at the f/48 Coude focus of 150 cm RTT150 telescope located at TUBITAK National Observatory (TUG) in Antalya/Turkey. The intensities, the local standard of rest (LSR) velocities ( V LSR ), and the linewidths (Full Width Half Maximum: FWHM) of the H α emission line from our observations were in the range of 84 to 745 Rayleigh ( R [one Rayleigh ( R) is 10 6/4 π photons cm −2 sr −1 s −1 = 2.4110 −7 erg cm −2 sr −1 s −1 at H α and corresponds to an emission measure ( EM = ∫ n e 2 dl ) of 2.3 pc cm −6 for a gas temperature of 8000 K, where n e is the averaged electron density within an emitting region in the interstellar medium; dl is distance element to the source region ( Haffner et al., 2003; Reynolds et al., 2005), 3 to −43 km s −1 and 30 to 73 km s −1, respectively. The LSR velocities and the linewidths from the data were obtained and compared with early results. We found that our results are in close agreement with them. Moreover, associated stars of some of the H ii regions were updated by analyzing their location, velocities, and brightness.