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1.
We map the dark molecular cloud core of L134 in the C18O (J = 1 - 0) emission line using the PMO 13.7m telescope, and present a contour map of integrated intensity of C18O (J = 1 - 0) emission. The C18O cloud is inside the distribution of extinction AB, the visual extinction of blue light, as well as inside the 13CO cloud in the L134 region. The depletion factors in this C18O cloud are generally greater than unity, which means there is gas depletion onto dust. Since only a minimum AB = 9.7 mag is available, and our observations measure both undepleted and depleted regions along the line of sight, the depletion factors could very likely be larger in the central core than the calculated value. So we conclude that depletion does occur in the bulk of the C18O cloud through a comparison between the C18O and blue extinction maps in the L134 region. There is no direct evidence as yet for star formation in L134, and so cores on the verge of collapse will not be visible in CO and other gas molecules.  相似文献   

2.
Previous observations have revealed an accretion disk and outflow motion in the high-mass starforming region G192.16–3.84, but collapse has not been reported before. Here we present molecular line and continuum observations toward the massive core G192.16–3.84 with the Submillimeter Array. C18 O(2–1) and HCO+(3–2) lines show pronounced blue profiles, indicating gas infalling in this region. This is the first time that infall motion has been reported in the G192.16–3.84 core. Two-layer model fitting gives infall velocities of 2.0±0.2 and 2.8±0.1 km s-1. Assuming that the cloud core follows a power-law density profile(ρ∝ r1.5), the corresponding mass infall rates are(4.7±1.7)×10-3 and(6.6±2.1)×10-3 M⊙yr-1 for C18 O(2–1) and HCO+(3–2), respectively. The derived infall rates are in agreement with the turbulent core model and those in other high-mass star-forming regions, suggesting that high accretion rate is a general requirement for forming a massive star.  相似文献   

3.
We present Caltech Submillimeter Observatory CO(2–1) and Spitzer IRAC observations toward IRAS 22506+5944, which is a 10~4 L_⊙massive star-forming region. The CO(2–1) maps show an east-west bipolar molecular outflow originating from the 3 mm dust continuum peak. The Spitzer IRAC color-composite image reveals a pair of bow-shaped tips which are prominent in excess 4.5 μm emission and are located at the leading fronts of the bipolar outflow, providing compelling evidence for the existence of bow-shocks as the driving agents of the molecular outflow. By comparing our CO(2–1) observations with previously published CO(1–0) data, we find that the CO(2–1)/(1–0) line ratio increases from low(~5 kms~(-1)) to moderate(~8–12 kms~(-1)) velocities, and then decreases at higher velocities. This is qualitatively consistent with the scenario that the molecular outflow is driven by multiple bow-shocks. We also revisit the position-velocity diagram of the CO(1–0) data, and find two spur structures along the outflow axis, which are further evidence for the presence of multiple jet bowshocks. Finally, power-law fittings to the mass spectrum of the outflow gives power law indexes more consistent with the jet bow-shock model than the wide-angle wind model.  相似文献   

4.
We present an exercise that intends to establish a relationship between the strength of nebular emission lines and optical stellar features in the spectrum of a galaxy. After accurately subtracting the stellar continuum and the underlying stellar absorption, we made reliable measurements of the emission lines of all the galaxies in the Sloan Digital Sky Survey Data Release 2 (SDSS DR2). More than 4000 star-forming galaxies with high S/N ratio of both the stellar spectrum and the emission lines are selected. These galaxy spectra are fitted with the 10 PCs of Yip et al., after all the emission line regions have been filtered out. We find that the flux of hydrogen Balmer emission lines, Hα and Hβ can be well recovered from the PCs, while the metal lines are not well reproduced. The fluxes of Hα and Hβ measured from the PC-reconstructed spectra and from the observed spectra agree well with an rms scatter of only - 0.1 dex. This result suggests that, with moderate spectral resolution and S/N ratio, the optical stellar spectrum of a galaxy can serve as an indicator of star formation rate.  相似文献   

5.
Ellerman bombs(EBs) are small brightening events in the solar lower atmosphere.By their original definition,the main characteristic of EBs is the two emission bumps in both wings of chromospheric lines,such as Hα and CaII 8542  lines.Up to now,most authors have found that the temperature increase of EBs around the temperature minimum region is in the range of 600–3000 K.However,with recent IRIS observations,some authors proposed that the temperature increase of EBs could be more than 10000 K.Using non-LTE semi-empirical modeling,we investigate the line profiles,continuum emission and radiative losses for EB models with different temperature increases,and compare them with observations.Our result indicates that if the EB maximum temperature reaches more than 10000 K around the temperature minimum region,then the resulting Hα and CaII 8542  line profiles and the continuum emission would be much stronger than those of EB observations.Moreover,due to the high radiative losses,a high temperature EB would have a very short lifetime,which is not compatible with observations.Thus,our study does not support the proposal that EB temperatures are higher than 10000 K.  相似文献   

6.
Variations of the Hα line in the spectra of the star HD14134 are investigated using observations carried out in 2013–2014 and in 2016 with the 2-m telescope at Shamakhy Astrophysical Observatory.In the spectra of this star,the absorption and emission components of Hα are found to disappear and an inverse P Cyg profile of Hα is seen on some observational epochs.Our observations showed that when the Hα line disappeared or an inversion of the P-Cyg-type profile is observed in the spectra,the Hβ line is redshifted.When these events appeared,no synchronous variabilities were observed in the spectral parameters of other spectral lines formed in deeper atmospheric layers.In addition,the structures of Hα,CII(6578.05 ,6582.88 ),SiII(6347.1 ,6371.36 ) and Hβ lines are variable on a timescale of hours,but we did not detect significant variations in the other photospheric lines,as well as in the HeI(5875.72 ) line.It is suggested that observational evidence for the non-stationary atmosphere of HD14134 can be associated in part with non-spherical stellar wind.  相似文献   

7.
The excitation of H2O masers usually needs very high density gas, hence it can serve as a marker of dense gas in HII region. We selected a sample of H2O maser sources from Plume et al. (four with, and four without detected CS(J = 7-6) emission), and observed them in 13CO(J=1-0) and C18O (J=1-0). C18O (J=1-0) emission was detected only in three of the sources with detected CS(J=7-6) emission. An analysis combined with some data in the literature suggests that these dense cores may be located at different evolutionary stages. Multi-line observation study may provide us clues on the evolution of massive star forming regions and the massive stars themselves.  相似文献   

8.
We present a catalog including 11 204 spectra of 10 436 early-type emission-line stars from LAMOST DR2, among which 9752 early-type emission-line spectra are newly discovered. For these earlytype emission-line stars, we discuss the morphological and physical properties of their low-resolution spectra. In this spectral sample, the Hα emission profiles display a wide variety of shapes. Based on the Hα line profiles, these spectra are categorized into five distinct classes: single-peak emission, single-peak emission in absorption, double-peak emission, double-peak emission in absorption, and P-Cygni profiles. To better understand what causes the Hα line profiles, we divide these objects into four types from the perspective of physical classification, which include classical Be stars, Herbig Ae/Be stars, close binaries and spectra contaminated by H II regions. The majority of Herbig Ae/Be stars and classical Be stars are identified and separated using a(H-K, K-W1) color-color diagram. We also discuss 31 binary systems that are listed in the SIMBAD on-line catalog and identify 3600 spectra contaminated by H II regions after cross-matching with positions in the Dubout-Crillon catalog. A statistical analysis of line profiles versus classifications is then conducted in order to understand the distribution of Hα profiles for each type in our sample. Finally, we also provide a table of 172 spectra with Fe II emission lines and roughly calculate stellar wind velocities for seven spectra with P-Cygni profiles.  相似文献   

9.
We report the FCRAO observations that mapped HCN(1–0), CS(2–1), HNC(1–0) and HCO+(1–0) in ten high-mass star forming cores associated with water masers. We present velocity integrated intensity maps of the four lines for these dense cores, compare their line profiles, and derive physical properties of these cores. We find that these four tracers identify areas with similar properties in these massive dense cores, and in most cases, the emissions of HCN and HCO+are stronger than those of HNC and CS. We also use the line ratios of HCO+/HCN, HNC/HCN and HNC/HCO+as the diagnostics to explore the environment of these high-mass star forming regions, and find that most of the cores agree with the model that photodominated regions dominate the radiation field, except for W44, for which the radiation field is similar to an X-ray dominated region.  相似文献   

10.
We obtained new high-resolution spectra using the Lijiang 1.8-m and 2.4-m telescopes to investigate the chromospheric activities of VI355 Ori as indicated in the behaviors of Ca Ⅱ HK,Hδ,Hγ,Hβ,Na Ⅰ D_1,D_2,Hα and Ca Ⅱ infrared triplet(IRT) lines.The observed spectra show obvious emissions above the continuum in Ca II HK lines,absorptions in the Hδ,Hγ,Hβ and Na Ⅰ D_1,D_2 lines,variable behavior(filled-in absorption,partial emission with a core absorption component or emission above the continuum)in the Hα line,and weak self-reversal emissions in the strong filled-in absorptions of the Ca Ⅱ IRT lines.We used a spectral subtraction technique to analyze our data.The results show no excess emission in the Hδ and Hγ lines,very weak excess emissions in the Na Ⅰ D_1,D_2 lines,excess emission in the Hβ line,clear excess emission in the Hα line,and excess emissions in the Ca Ⅱ IRT lines.The value of the ratio of EW_(8542)/EW_(8498) is in the range 0.9 to 1.7,which implies that chromospheric activity might have been caused by plage events.The value of the ratio E_(Hα)/E_(Hβ) is above 3,indicating that the Balmer lines would arise from prominence-like material.We also found time variations in light curves associated with equivalent widths of chromospheric activity lines in the Na Ⅰ D_1,D_2,Ca Ⅱ IRT and Hα lines in particular.These phenomena can be explained by plage events,which are consistent with the behavior of chromospheric activity indicators.  相似文献   

11.
We present simultaneous observations of 12CO,13CO and C18O J=1-0 emission in 11 nearby(cz<1000 km s-1) bright infrared galaxies.Both 12CO and 13CO are detected in the centers of all the galaxies,except for 13CO in NGC 3031. We have also detected C18O,CSJ=2-1 and HCO+J=1-0 emission in the nuclear regions of M82 and M51.These are the first systematical extragalactic detections of 12CO and its isotopes from the PMO 14 m telescope.We have conducted half-beam-spaced mapping of M82 over an area of 4×2.5 and major...  相似文献   

12.
We analyze oscillation behaviours in chromospheric internetwork regions using spectral observations of the CⅡ1334 A line obtained with the Solar Ultraviolet Measurements of Emitted Radiation spectrograph (SUMER) aboard Solar and Heliospheric Observatory (SOHO). Three areas, 26 ×120arcsec2 each, at the various latitudes from the disk center to the north polar coronal hole, were rastered with a cadence of about 40-60 s in the solar minimum year. We obtained the time evolution of two-dimensional (2D) line intensity, continuum and line core shift. The continuum and the line shift show -3 min chromospheric oscillations in the internetwork regions underlying the coronal hole as well as at the disk center. We find that the CⅡ1334A line shift oscillates with an average speed of -1.7 km s-1, independent of the latitude, while its coherent scale decreases with latitude. On the other hand, the oscillation amplitude of the continuum around the 1334 A and the phase delay between the Doppler shift and continuum sli  相似文献   

13.
We present a multi-transition study to investigate the physical properties of dust and molecular gas in the archetypical merger Arp 299 by using data including James Clerk Maxwell Telescope(JCMT)850 and 450 μm observations, Herschel 500, 350, 250, 160 and 70 μm continuum maps, as well as the CO(3–2), CO(4–3) low-J CO lines and CO(11–10), CO(13–12), CO(14–13) high-J CO lines. The CO(3–2) and CO(4–3) lines are observed by JCMT, and the CO(11–10), CO(13–12), CO(14–13) lines are available on the Herschel Science Archive. The resolution of the Herschel Spectral and Photometric Imaging Receiver(SPIRE) Fourier transform spectrometer(FTS) CO(11–10) data is similar to that of the JCMT CO(3–2) line, while the resolution of the SPIRE/FTS CO(13–12) and Photodetector Array Camera and Spectrometer(PACS) CO(14–13) data is similar to that of JCMT CO(4–3), allowing us to obtain accurate line ratios of I_(CO(11-10))/I_(CO(3-2)), I_(CO(13-12))/I_(CO(4-3))and I_(CO(14-13))/I_(CO(4-3)).By modeling the spectral energy distribution of the continuum data, we conclude that two components(cold and warm) exist in the dust, with the warm component occupying a small percent of the total dust mass. We further use a radiative transfer analysis code, RADEX, to calculate the density, temperature and column density of warm gas in the central region, which shows that the kinetic temperature Tkinis in the range 110 to 150 K and hydrogen density n(H_2) is in the range 10~(4.7)-10~(5.5)cm~(-3). We show that the hot dust is located in the central region of IC 694 with a radius of ~ 4′′and estimate that the warm gas mass is in the range 3.8 × 10~7M_⊙ to 7.7 × 10~7M_⊙, which contains 5.0%–15.0% of the total H_2 mass for the region of IC 694. We also calculate the star formation rate of the galaxy in particular,which is much higher than that of the Milky Way.  相似文献   

14.
We present the results obtained from detailed timing and spectral studies of the Be/X-ray binary pulsar KS 1947+300 during its 2013 giant outburst. We used data from Suzaku observations of the pulsar at two epochs, i.e. on 2013 October 22(close to the peak of the outburst) and 2013 November 22. Xray pulsations at ~18.81 s were clearly detected in the light curves obtained from both observations. Pulse periods estimated during the outburst showed that the pulsar was spinning up. The pulse profile was found to be single-peaked up to ~10 ke V beyond which a sharp peak followed by a dip-like feature appeared at hard X-rays. The dip-like feature has been observed up to ~70 keV. The 1–110 ke V broad-band spectroscopy of both observations revealed that the best-fit model was comprised of a partially absorbed Negative and Positive power law with EXponential cutoff(NPEX) continuum model along with a blackbody component for the soft X-ray excess and two Gaussian functions at 6.4 and 6.7 ke V for emission lines. Both the lines were identified as emission from neutral and He-like iron atoms. To fit the spectra, we included the previously reported cyclotron absorption line at 12.2 keV. From the spin-up rate, the magnetic field of the pulsar was estimated to be ~1.2×10~(12)G and found to be comparable to that obtained from the detection of the cyclotron absorption feature. Pulse-phase resolved spectroscopy revealed the pulsating nature of the soft X-ray excess component in phase with the continuum flux. This confirms that the accretion column and/or accretion stream are the most probable regions of the soft X-ray excess emission in KS1947+300.The presence of the pulsating soft X-ray excess in phase with continuum emission may be the possible reason for not observing the dip at soft X-rays.  相似文献   

15.
NGC 1266 is a lenticular galaxy(S0) hosting an active galactic nucleus(AGN), and known to contain a large amount of shocked gas. We compare the luminosity ratio of mid-J CO lines to IR continuum with star-forming galaxies(SFGs), and then model the CO spectral line energy distribution(SLED). We confirm that in the mid-and high-J regions(Jup= 4–13), the C-type shock(vs= 25 km s-1, nH= 5 × 104cm-3) can reproduce the CO observations w...  相似文献   

16.
One of the popular models for the low/hard state of black hole binaries is that the standard accretion disk is truncated and the hot inner region produces, via Comptonization, hard X-ray flux.This is supported by the value of the high energy photon index, which is often found to be small,～ 1.7( 2), implying that the hot medium is starved of seed photons. On the other hand, the suggestive presence of a broad relativistic Fe line during the hard state would suggest that the accretion disk is not truncated but extends all the way to the innermost stable circular orbit. In such a case, it is a puzzle why the hot medium would remain photon starved. The broad Fe line should be accompanied by a broad smeared reflection hump at ～ 30 ke V and it may be that this additional component makes the spectrum hard and the intrinsic photon index is larger, i.e. 2. This would mean that the medium is not photon deficient, reconciling the presence of a broad Fe line in the observed hard state. To test this hypothesis,we have analyzed the RXTE observations of GX 339–4 from the four outbursts during 2002–2011 and identify observations when the system was in the hard state and showed a broad Fe line. We have then attempted to fit these observations with models, which include smeared reflection, to understand whether the intrinsic photon index can indeed be large. We find that, while for some observations the inclusion of reflection does increase the photon index, there are hard state observations with a broad Fe line that have photon indices less than 2.  相似文献   

17.
Key Properties of Solar Chromospheric Line Formation Process   总被引：1，自引：0，他引：1  
The distribution or wavelength-dependence of the formation regions of frequently used solar lines, Hα，Hβ，CaIIH and CaII8542,in quiet Sun,faint and bright flares is explored in the unpolarized case.We stress four aspects characterising the property of line formation process:1) width of line formation core;2) line formation region;3)influence of the temperature minimum region; and 4) wavelength ranges within which one can obtain pure chromospheric and photospheric filtergrams.It is shown that the above four aspects depend strongly on the atmospheric physical condition and the lines used. The formation regions of all the wavelength points within a line may be continuously distributed over one depth domain or discretely distributed because of no contribution coming from the temperature minimum region, an important domain in the solar atmosphere that determines the distribution pattern of escape photons. On the other hand, the formation region of one wavelength point may cover only one height range or spread over two domains which are separated again by the temperature minimum region. Different lines may form in different regions in the quiet Sun. However, these line formation regions become closer in solar flaring regions. Finally, though the stratification of line-of-sight velocity can alter the position of the line formation core within the line band and result in the asymmetry of the line formation core about the shifted line center, it can only lead to negligible changes in the line formation region or the line formation core width. All these results can be instructive to solar filtering observations.  相似文献   

18.
We performed time resolved spectroscopy of 1H0707–495 and IRAS 13224–3809 using long XMM-Newton observations. These are strongly variable narrow line Seyfert 1 galaxies and show broad features around 1 ke V that have been interpreted as relativistically broad Fe Lα lines. Such features are not clearly observed in other active galactic nuclei despite sometimes having high iron abundance required by the best fitted blurred reflection models. Given the importance of these lines, we explore whether the rapid variability of spectral parameters may introduce broad bumps/dips artificially in the time averaged spectrum, which may then be mistaken as broadened lines. We tested this hypothesis by performing time resolved spectroscopy using long(100 ks) XMM-Newton observations and by dividing them into segments with typical exposures of a few ks. We extracted spectra from each such segment and modeled them using a two component phenomenological model consisting of a power law to represent the hard component and a black body to represent the soft emission. As expected, both the sources showed variations in the spectral parameters. Using these variation trends, we simulated model spectra for each segment and then co-added to get a combined simulated spectrum. In the simulated spectra, we found no broad features below 1 ke V and in particular no deviation near 0.9 ke V as seen in the real averaged spectra. This implies that the broad Fe Lα line that is seen in the spectra of these sources is not an artifact of the variation of spectral components and, hence, provides evidence that the line is indeed genuine.  相似文献   

19.
Many galaxies are thought to contain massive black holes, with masses in excess of ten million solar masses, at their centres and warped circumnu-clear toruses. The best evidence comes from observing gas or masers rotating rapidly within a circumnuclear torus surrounding a central body. Here we report on the first MERLIN observations of line emission from the OH megamaser toward IRAS 10173+0828. The position of peak flux contours of the OH megamaser is consistent with that of the continuum in IRAS 10173+0828. This means that the OH megamaser is a diffuse unsaturated maser which could amplify the diffuse 18 cm continuum emission with an amplification factor of order unity.  相似文献   

20.
Planetary nebulae(PNe) are an important tool for studying the dynamics and chemical evolution of galaxies in the Local Universe, given their characteristic bright emission line spectra. The Andromeda Galaxy(M31) provides a unique laboratory for studying PNe in the circumnuclear region,thanks to its proximity and almost uniformly low line-of-sight extinction that ensures observations with high resolution and sensitivity. Using the WIYN/Hydra multi-fiber spectrograph, we have obtained optical(4119–6882 A?) spectra of 77 PN candidates selected from Hubble Space Telescope narrow-band imaging, which are located within the central ~500 pc region of M31. Among these candidates, 49(64%) are spectroscopically observed for the first time. The spectra of 300 previously known PNe and H Ⅱ regions, which primarily reside in the disk, are also taken for comparison. All 77 circumnuclear PN candidates exhibit prominent emission lines, including [O Ⅲ]λ5007, [N Ⅱ]λ6583, Hα and Hβ,strongly suggesting that they are genuine PNe. We measured the line fluxes, radial velocities and line widths for all objects, and found that the radial velocities of the circumnuclear PNe generally trace rotation of the inner bulge. We also estimated a dynamical mass of ~6.4±0.5×10~9 M_⊙ enclosed within an effective galactocentric radius of 340 pc, which is compatible with the previously estimated total stellar mass in this region.  相似文献   

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