The observation of oxygen(O)-and nitrogen(N)-bearing molecules gives an idea about the complex prebiotic chemistry in the interstellar medium.Recent millimeter and submillimeter wavelength observations have shown the ...The observation of oxygen(O)-and nitrogen(N)-bearing molecules gives an idea about the complex prebiotic chemistry in the interstellar medium.Recent millimeter and submillimeter wavelength observations have shown the presence of complex O-and N-bearing molecules in the star formation regions.So,the investigation of those molecules is crucial to understanding the chemical complexity in the star-forming regions.In this article,we present the identification of the rotational emission lines of N-bearing molecules ethyl cyanide(C_(2)H_(5)CN)and cyanoacetylene(HC_(3)N),and O-bearing molecule methyl formate(CH_(3)OCHO)toward high-mass protostar IRAS18089–1732 using the Atacama Compact Array.We also detected the emission lines of both the N-and O-bearing molecule formamide(NH_(2)CHO)in the envelope of IRAS 18089–1732.We have detected the v=0 and 1 state rotational emission lines of CH_(3)OCHO.We also detected the two vibrationally excited states of HC_(3)N(v7=1 and v7=2).The estimated fractional abundances of C_(2)H_(5)CN,HC_(3)N(v7=1),HC_(3)N(v7=2),and NH_(2)CHO toward IRAS 18089–1732 are(1.40±0.5)×10^(-10),(7.5±0.7)×10^(-11),(3.1±0.4)×10^(-11),and(6.25±0.82)×10^(-11)respectively.Similarly,the estimated fractional abundances of CH_(3)OCHO(v=0)and CH_(3)OCHO(v=1)are(1.90±0.9)×10^(-9)and(8.90±0.8)×10^(-10),respectively.We also created the integrated emission maps of the detected molecules,and the observed molecules may have originated from the extended envelope of the protostar.We show that C_(2)H_(5)CNand HC_(3)N are most probably formed via the subsequential hydrogenation of the CH_(2)CHCNand the reaction between C_(2)H_(2)and CN on the grain surface of IRAS 18089–1732.We found that NH_(2)CHO is probably produced due to the reaction between NH_(2)and H_(2)CO in the gas phase.Similarly,CH_(3)OCHO is possibly created via the reaction between radical CH_(3)O and radical HCO on the grain surface of IRAS 18089–1732.展开更多
We fit various color–magnitude diagrams(CMDs) of the high-latitude Galactic globular clusters NGC 5024(M53),NGC 5053,NGC 5272(M3),NGC 5466,and NGC 7099(M30) by isochrones from the Dartmouth Stellar Evolution Database...We fit various color–magnitude diagrams(CMDs) of the high-latitude Galactic globular clusters NGC 5024(M53),NGC 5053,NGC 5272(M3),NGC 5466,and NGC 7099(M30) by isochrones from the Dartmouth Stellar Evolution Database and Bag of Stellar Tracks and Isochrones for α–enrichment [α/Fe] = +0.4.For the CMDs,we use data sets from Hubble Space Telescope,Gaia,and other sources utilizing,at least,25 photometric filters for each cluster.We obtain the following characteristics with their statistical uncertainties for NGC 5024,NGC 5053,NGC 5272,NGC 5466,and NGC 7099,respectively:metallicities [Fe/H] =-1.93 ± 0.02,-2.08 ± 0.03,-1.60 ± 0.02,-1.95 ± 0.02,and-2.07 ± 0.04 dex with their systematic uncertainty 0.1 dex;ages 13.00 ± 0.11,12.70 ± 0.11,11.63 ± 0.07,12.15 ± 0.11,and 12.80 ± 0.17 Gyr with their systematic uncertainty 0.8 Gyr;distances(systematic uncertainty added) 18.22 ± 0.06 ± 0.60,16.99 ± 0.06 ± 0.56,10.08 ± 0.04 ± 0.33,15.59 ±0.03 ± 0.51,and 8.29 ± 0.03 ± 0.27 kpc;reddenings E(B-V) = 0.023 ± 0.004,0.017 ± 0.004,0.023 ± 0.004,0.023 ± 0.003,and 0.045 ± 0.002 mag with their systematic uncertainty 0.01 mag;extinctions AV= 0.08 ± 0.01,0.06 ± 0.01,0.08 ± 0.01,0.08 ± 0.01,and 0.16 ± 0.01 mag with their systematic uncertainty 0.03 mag,which suggest the total Galactic extinction AV= 0.08 across the whole Galactic dust to extragalactic objects at the North Galactic Pole.The horizontal branch morphology difference of these clusters is explained by their different metallicity,age,mass-loss efficiency,and loss of low-mass members in the evolution of the core-collapse cluster NGC 7099 and loose clusters NGC 5053 and NGC 5466.展开更多
We present multi-wavelength imagery of the merger remnant galaxy NGC 1316 with an objective to study the dust content and its association with the other phases of the interstellar medium. Color-index maps as well as e...We present multi-wavelength imagery of the merger remnant galaxy NGC 1316 with an objective to study the dust content and its association with the other phases of the interstellar medium. Color-index maps as well as extinction maps derived for this galaxy reveal an intricate and complex dust morphology in NGC 1316, i.e. there is a prominent lane in the inner part, while at about 6-7 kpc it apparently takes the form of an arc-like pattern extending along the northeast direction. In addition to this, several other dust clumps and knots are also evident in this galaxy. The dust emission mapped using Spitzer data at 8 μm indicates even more complex morphological structures of the dust in NGC 1316. The extinction curve derived over the optical to near-IR bands closely follows the standard Galactic curve, suggesting similar properties of the dust grains. The dust content of NGC 1316, estimated from optical extinction, is ,- 2.13 × 10^5 M⊙. This is a lower limit compared to that estimated using the IRAS flux densities of ,-5.17× 10^6 M⊙ and the flux densities at 24, 70 and 160 p.m from MIPS ,-3.2× 10^7 M⊙. High resolution Chandra observations of this merger remnant system have provided an unprecedented view of the complex nature exhibited by the distribution of hot gas in NGC 1316, which closely matches the morphology of ionized gas and to some extent also the dust. X-ray color-color plots for the resolved sources within the optical D25 extent of NGC 1316 have enabled us to separate them into different classes.展开更多
A multiwavelength study of a nearby dust lane early-type galaxy IC 5063 is presented. The objectives are to investigate dust extinction properties and the association of interstellar dust with other phases of ISM. The...A multiwavelength study of a nearby dust lane early-type galaxy IC 5063 is presented. The objectives are to investigate dust extinction properties and the association of interstellar dust with other phases of ISM. The color-index maps as well as the extinction maps derived from the analysis of deep CCD observations in optical passbands revealed a prominent dust lane along its optical major axis in the inner region. In addition, two more fainter and extended dust patterns are apparent in the color index map as well as extinction maps. These features are also evident in the smooth model subtracted residual maps. The extinction curve derived for this galaxy revealed that dust grains in it are identical to the canonical grains in the Milky Way with the dust grains little larger than the canonical grains. The total extinction measured in the V band extinction map enabled us to quantify the dust content of this galaxy to be equal to , an order of magnitude shorter than that estimated using the IRAS flux densities at 60 and 100 μm. A Multiphase ISM study revealed a surprising similarity in the morphologies of the Hα emitting ionized gas distribution and X-ray emitting gas. Systematic analysis of high resolution X-ray observations using Chandra telescope enabled us to detect 18 discrete X-ray sources within optical D25 region of IC 5063, out of which 17 sources were separated out as the low mass X-ray binaries and one as the high mass X-ray binary source in the X-ray color-color plot.展开更多
I identify a point-symmetric structure in recently published VLT/MUSE velocity maps of different elements in a plane along the line of sight at the center of the supernova remnant SNR 0540-69.3,and argue that jitterin...I identify a point-symmetric structure in recently published VLT/MUSE velocity maps of different elements in a plane along the line of sight at the center of the supernova remnant SNR 0540-69.3,and argue that jittering jets that exploded this core collapse supernova shaped this point-symmetric structure.The four pairs of two opposite clumps that compose this point symmetric structure suggest that two to four pairs of jittering jets shaped the inner ejecta in this plane.In addition,intensity images of several spectral lines reveal a faint strip(the main jet-axis)that is part of this plane of jittering jets and its similarity to morphological features in a few other SNRs and in some planetary nebulae further suggests shaping by jets.My interpretation implies that in addition to instabilities,jets also mix elements in the ejecta of core collapse supernovae.Based on the point-symmetric structure and under the assumption that jittering jets exploded this supernova,I estimate the component of the neutron star natal kick velocity on the plane of the sky to be■235 km s^(-1),and at an angle of■47°to the direction of the main jet-axis.I analyze this natal kick direction together with 12 other SNRs in the frame of the jittering jets explosion mechanism.展开更多
Dust extinction law is crucial to recover the intrinsic energy distribution of celestial objects and infer the characteristics of interstellar dust.Based on the traditional pair method,an improved pair method is propo...Dust extinction law is crucial to recover the intrinsic energy distribution of celestial objects and infer the characteristics of interstellar dust.Based on the traditional pair method,an improved pair method is proposed to model the dust extinguished spectral energy distribution(SED)of an individual star.Instead of the mathematically parameterizing extinction curves,the extinction curves in this work are directly from the silicate-graphite dust model,so that the dust extinction law can be obtained and the dust properties can be analyzed simultaneously.The ATLAS9 stellar model atmosphere is adopted for the intrinsic SEDs in this work,while the silicate-graphite dust model with a dust size distribution of dn da~a^(-a)exp(-a a_(c)),0.005<a<5μmfor each component is adopted for the model extinction curves.One typical extinction tracer in the dense region(V410 Anon9)and one in the diffuse region(Cyg OB2#12)of the Milky Way are chosen to test the reliability and the practicability of the improved pair method in different stellar environments.The results are consistent with their interstellar environments and are in agreement with the previous observations and studies,which prove that the improved pair method is effective and applicable in different stellar environments.In addition to the reliable extinction results,the derived parameters in the dust model can be used to analyze the dust properties,which cannot be achieved by other methods with the mathematical extinction models.With the improved pair method,the stellar parameters can also be inferred and the extinction law beyond the wavelengths of observed data can be predicted based on the dust model as well.展开更多
We present high spatial resolution X-ray spectroscopy of the supernova remnant Cassiopeia A with the Chandra observations. The X-ray emitting region of this remnant was divided into 38 × 34 pixels of 10″× 1...We present high spatial resolution X-ray spectroscopy of the supernova remnant Cassiopeia A with the Chandra observations. The X-ray emitting region of this remnant was divided into 38 × 34 pixels of 10″× 10″ each. Spectra of 960 pixels were created and fitted with an absorbed two component non-equilibrium ionization model. From the results of the spectral analysis we obtained maps of absorbing column density, temperatures, ionization ages, and the abundances of Ne, Mg, Si, S, Ca and Fe. The Si, S and possibly Ca abundance maps show obvious jet structures, while Fe does not follow the jet but seems to be distributed perpendicular to it. The abundances of Si, S and Ca show tight correlations between one another over a range of about two dex. This suggests that they are ejecta from explosive O- burning and incomplete Si-burning. Meanwhile, the Ne abundance is well correlated with that of Mg, indicating them to be the ashes of explosive C/Ne burning. The Fe abundance is positively correlated with that of Si when the latter is lower than 3 times the solar value, and is negatively correlated when higher. We suggest that such a two phase correlation is due to the different ways in which Fe was synthesized.展开更多
Galactic transient black hole candidate(BHC)MAXI J1836–194 was discovered on 2011 Aug30,by MAXI/GSC and Swift/BAT.The source activity during this outburst continued for^3 months before entering into the quiescent sta...Galactic transient black hole candidate(BHC)MAXI J1836–194 was discovered on 2011 Aug30,by MAXI/GSC and Swift/BAT.The source activity during this outburst continued for^3 months before entering into the quiescent state.It again became active in March 2012 and continued for another^2 months.In this paper,3-25 keV RXTE/PCA spectra from the 2011 outburst and 0.5-10.0 keV Swift/XRT data during its 2012 outburst are analyzed with the two-component advective flow(TCAF)model based fits files in XSPEC.We calculate the X-ray contributions coming from jets/outflow using a newly developed method based on the deviation of the TCAF model normalization.We also study the correlation between observed radio and estimated jet X-ray fluxes.The correlation indices(b)are found to be 1.79 and 0.61,when the 7.45 GHz Very Large Array(VLA)radio flux is correlated with the total X-ray and jet X-ray fluxes in 3-25 keV range respectively.It has been found that the jet contributes in X-rays up to a maximum of 86%during its 2011 outburst.This makes the BHC MAXI J1836–194 strongly jet dominated during the initial rising phase.展开更多
We present high spatial resolution X-ray spectroscopy of supernova rem- nant G292.0+1.8 made with Chandra observations. The X-ray emitting region of this remnant was divided into 25 × 25 pixels with a scale of 2...We present high spatial resolution X-ray spectroscopy of supernova rem- nant G292.0+1.8 made with Chandra observations. The X-ray emitting region of this remnant was divided into 25 × 25 pixels with a scale of 20" × 20" each. Spectra of 328 pixels were created and fitted with an absorbed one component non-equilibrium ionization model. With the spectral analysis results, we obtained maps of absorbing column density, temperature, ionization age and abundances for O, Ne, Mg, Si, S and Fe. The abundances of O, Ne and Mg show tight correlations between each other in the range of about two orders of magnitude, suggesting that they are all from explo- sive C/Ne burning. Meanwhile, the abundances of Si and S are also well correlated, indicating that they are the ashes of explosive O-burning or incomplete Si-burning. The Fe emission lines are not prominent in the whole remnant, and their abundance is significantly reduced, indicating that the reverse shock may not have propagated to the Fe-rich ejecta. Based on relative abundances of O, Ne, Mg, Si and Fe to Si, we suggest a progenitor mass of 25 - 30 M⊙ for this remnant.展开更多
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 obser...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.展开更多
We have conducted a large-field simultaneous survey of 12 CO,13 CO and C18O J=1-0 emission toward the Orion A giant molecular cloud(GMC)with a sky coverage of4.4 deg2 using the Purple Mountain Observatory(PMO)-13.7 m ...We have conducted a large-field simultaneous survey of 12 CO,13 CO and C18O J=1-0 emission toward the Orion A giant molecular cloud(GMC)with a sky coverage of4.4 deg2 using the Purple Mountain Observatory(PMO)-13.7 m millimeter-wavelength telescope.We use the probability distribution function of the column density(N-PDF)to investigate the distribution of molecular hydrogen in the Orion A GMC.The H2 column density,derived from the 13CO emission,of the GMC is dominated by a log-normal distribution in the range from4×1021 to1.5×1023 cm-2 with excesses both at the low-density and high-density ends.The excess of the low-density end is possibly caused by an extended and low-temperature(10 K)component with velocities in the range of 5-8 km s-1.Compared with the northern sub-regions,the southern sub-regions of the Orion A GMC contain less gas with column density in NH2>1.25×1022 cm-2.The dispersions of the N-PDFs of the sub-regions are found to correlate with the evolutionary stages of the clouds across the Orion A GMC.The structure hierarchy of Orion A GMC is explored with the DENDROGRAM algorithm,and it is found that the GMC is composed of two branches.All structures except one in the tree have virial parameters less than 2,indicating self-gravity is important on the spatial scales from0.3 to4 pc.Although power-laws and departures from lognormal distributions are found at the high-density end of N-PDFs for active star-forming regions,the N-PDFs of structures in the Orion A GMC are predominantly lognormal on scales from R0.4 to 4 pc.展开更多
We have carried out observations of 12CO J=2-1 and 12CO J=3-2 to- ward the high-mass protostellar candidate IRAS 20188+3928. Compared with previ- ous observations, the 12CO J=2-1 and 12CO J=3-2 lines both have asymme...We have carried out observations of 12CO J=2-1 and 12CO J=3-2 to- ward the high-mass protostellar candidate IRAS 20188+3928. Compared with previ- ous observations, the 12CO J=2-1 and 12CO J=3-2 lines both have asymmetric pro- files with an absorption dip. The velocity of the absorption dip is ~ 1.0 km s-1. The spectral shape may be caused by rotation. The velocity-integrated intensity map and position-velocity diagram of the 12CO J=2-1 line present an obvious bipolar com- ponent, further verifying that this region has an outflow motion. This region is also associated with an HII region, an IRAS source, and an H20 maser. The H20 maser has the velocity of 1.1 km s-1. Compared with the components of the outflow, we find that the H20 maser is not associated with the outflow. Using the large velocity gradi- ent model, we concluded that possible averaged gas densities of the blueshifted lobe and redshifted lobe are 1.0x 105 cm-3 and 2.0x 104 cm-a, while kinetic temperatures are 26.9 K and 52.9 K, respectively. Additionally, the outflow has a higher integrated intensity ratio (Ico J=3 - 2/Ico J=2 - 1).展开更多
We have carried out CO J=2 - 1 and CO J = 3 - 2 observations toward Tycho's supernova remnant (SNR) using the KOSMA 3m-telescope. From these observations, we identified three molecular clouds (MCs) around the SNR...We have carried out CO J=2 - 1 and CO J = 3 - 2 observations toward Tycho's supernova remnant (SNR) using the KOSMA 3m-telescope. From these observations, we identified three molecular clouds (MCs) around the SNR. The small cloud in the southwest was discovered for the first time. In the north and east, two MCs (Cloud A and Cloud B) adjacent in space display a bow-shaped morphology, and have broad emission lines, which provide some direct evidences of the SNR-MCs interaction. The MCs are revealed at-69∽-59 km s-1, coincident with Tycho's SNR. The MCs associated with Tycho's SNR have a mass of-2.13 x 10^3 Mo. Position- velocity diagrams show the two clouds to be adjacent in velocity, which means cloud- cloud collision could occur in this region. The maximum value (0.66±0.10) of the integrated CO line intensity ratio (IcoJ=3-2/Icoj=2-1) for the three MCs agrees well with the previous measurement of individual Galactic MCs, implying that the SNR shock drove into the MCs. The two MCs have a line intensity ratio gradient. The distribution of the ratio appears to indicate that the shock propagates from the southwest to the northeast.展开更多
基金the Swami Vivekananda Merit-cum-Means Scholarship(SVMCM)for financial support for this research。
文摘The observation of oxygen(O)-and nitrogen(N)-bearing molecules gives an idea about the complex prebiotic chemistry in the interstellar medium.Recent millimeter and submillimeter wavelength observations have shown the presence of complex O-and N-bearing molecules in the star formation regions.So,the investigation of those molecules is crucial to understanding the chemical complexity in the star-forming regions.In this article,we present the identification of the rotational emission lines of N-bearing molecules ethyl cyanide(C_(2)H_(5)CN)and cyanoacetylene(HC_(3)N),and O-bearing molecule methyl formate(CH_(3)OCHO)toward high-mass protostar IRAS18089–1732 using the Atacama Compact Array.We also detected the emission lines of both the N-and O-bearing molecule formamide(NH_(2)CHO)in the envelope of IRAS 18089–1732.We have detected the v=0 and 1 state rotational emission lines of CH_(3)OCHO.We also detected the two vibrationally excited states of HC_(3)N(v7=1 and v7=2).The estimated fractional abundances of C_(2)H_(5)CN,HC_(3)N(v7=1),HC_(3)N(v7=2),and NH_(2)CHO toward IRAS 18089–1732 are(1.40±0.5)×10^(-10),(7.5±0.7)×10^(-11),(3.1±0.4)×10^(-11),and(6.25±0.82)×10^(-11)respectively.Similarly,the estimated fractional abundances of CH_(3)OCHO(v=0)and CH_(3)OCHO(v=1)are(1.90±0.9)×10^(-9)and(8.90±0.8)×10^(-10),respectively.We also created the integrated emission maps of the detected molecules,and the observed molecules may have originated from the extended envelope of the protostar.We show that C_(2)H_(5)CNand HC_(3)N are most probably formed via the subsequential hydrogenation of the CH_(2)CHCNand the reaction between C_(2)H_(2)and CN on the grain surface of IRAS 18089–1732.We found that NH_(2)CHO is probably produced due to the reaction between NH_(2)and H_(2)CO in the gas phase.Similarly,CH_(3)OCHO is possibly created via the reaction between radical CH_(3)O and radical HCO on the grain surface of IRAS 18089–1732.
基金financial support from the Russian Science Foundation (grant No.20-72-10052)。
文摘We fit various color–magnitude diagrams(CMDs) of the high-latitude Galactic globular clusters NGC 5024(M53),NGC 5053,NGC 5272(M3),NGC 5466,and NGC 7099(M30) by isochrones from the Dartmouth Stellar Evolution Database and Bag of Stellar Tracks and Isochrones for α–enrichment [α/Fe] = +0.4.For the CMDs,we use data sets from Hubble Space Telescope,Gaia,and other sources utilizing,at least,25 photometric filters for each cluster.We obtain the following characteristics with their statistical uncertainties for NGC 5024,NGC 5053,NGC 5272,NGC 5466,and NGC 7099,respectively:metallicities [Fe/H] =-1.93 ± 0.02,-2.08 ± 0.03,-1.60 ± 0.02,-1.95 ± 0.02,and-2.07 ± 0.04 dex with their systematic uncertainty 0.1 dex;ages 13.00 ± 0.11,12.70 ± 0.11,11.63 ± 0.07,12.15 ± 0.11,and 12.80 ± 0.17 Gyr with their systematic uncertainty 0.8 Gyr;distances(systematic uncertainty added) 18.22 ± 0.06 ± 0.60,16.99 ± 0.06 ± 0.56,10.08 ± 0.04 ± 0.33,15.59 ±0.03 ± 0.51,and 8.29 ± 0.03 ± 0.27 kpc;reddenings E(B-V) = 0.023 ± 0.004,0.017 ± 0.004,0.023 ± 0.004,0.023 ± 0.003,and 0.045 ± 0.002 mag with their systematic uncertainty 0.01 mag;extinctions AV= 0.08 ± 0.01,0.06 ± 0.01,0.08 ± 0.01,0.08 ± 0.01,and 0.16 ± 0.01 mag with their systematic uncertainty 0.03 mag,which suggest the total Galactic extinction AV= 0.08 across the whole Galactic dust to extragalactic objects at the North Galactic Pole.The horizontal branch morphology difference of these clusters is explained by their different metallicity,age,mass-loss efficiency,and loss of low-mass members in the evolution of the core-collapse cluster NGC 7099 and loose clusters NGC 5053 and NGC 5466.
基金supported by UGC, New Delhi under the major research project F.No. (36-240/2008-SR)the use of the High Performance Computing Facility developed under the DST- FIST scheme sanction No. SR/FST/PSI-145
文摘We present multi-wavelength imagery of the merger remnant galaxy NGC 1316 with an objective to study the dust content and its association with the other phases of the interstellar medium. Color-index maps as well as extinction maps derived for this galaxy reveal an intricate and complex dust morphology in NGC 1316, i.e. there is a prominent lane in the inner part, while at about 6-7 kpc it apparently takes the form of an arc-like pattern extending along the northeast direction. In addition to this, several other dust clumps and knots are also evident in this galaxy. The dust emission mapped using Spitzer data at 8 μm indicates even more complex morphological structures of the dust in NGC 1316. The extinction curve derived over the optical to near-IR bands closely follows the standard Galactic curve, suggesting similar properties of the dust grains. The dust content of NGC 1316, estimated from optical extinction, is ,- 2.13 × 10^5 M⊙. This is a lower limit compared to that estimated using the IRAS flux densities of ,-5.17× 10^6 M⊙ and the flux densities at 24, 70 and 160 p.m from MIPS ,-3.2× 10^7 M⊙. High resolution Chandra observations of this merger remnant system have provided an unprecedented view of the complex nature exhibited by the distribution of hot gas in NGC 1316, which closely matches the morphology of ionized gas and to some extent also the dust. X-ray color-color plots for the resolved sources within the optical D25 extent of NGC 1316 have enabled us to separate them into different classes.
文摘A multiwavelength study of a nearby dust lane early-type galaxy IC 5063 is presented. The objectives are to investigate dust extinction properties and the association of interstellar dust with other phases of ISM. The color-index maps as well as the extinction maps derived from the analysis of deep CCD observations in optical passbands revealed a prominent dust lane along its optical major axis in the inner region. In addition, two more fainter and extended dust patterns are apparent in the color index map as well as extinction maps. These features are also evident in the smooth model subtracted residual maps. The extinction curve derived for this galaxy revealed that dust grains in it are identical to the canonical grains in the Milky Way with the dust grains little larger than the canonical grains. The total extinction measured in the V band extinction map enabled us to quantify the dust content of this galaxy to be equal to , an order of magnitude shorter than that estimated using the IRAS flux densities at 60 and 100 μm. A Multiphase ISM study revealed a surprising similarity in the morphologies of the Hα emitting ionized gas distribution and X-ray emitting gas. Systematic analysis of high resolution X-ray observations using Chandra telescope enabled us to detect 18 discrete X-ray sources within optical D25 region of IC 5063, out of which 17 sources were separated out as the low mass X-ray binaries and one as the high mass X-ray binary source in the X-ray color-color plot.
基金supported by a grant from the Israel Science Foundation(769/20)。
文摘I identify a point-symmetric structure in recently published VLT/MUSE velocity maps of different elements in a plane along the line of sight at the center of the supernova remnant SNR 0540-69.3,and argue that jittering jets that exploded this core collapse supernova shaped this point-symmetric structure.The four pairs of two opposite clumps that compose this point symmetric structure suggest that two to four pairs of jittering jets shaped the inner ejecta in this plane.In addition,intensity images of several spectral lines reveal a faint strip(the main jet-axis)that is part of this plane of jittering jets and its similarity to morphological features in a few other SNRs and in some planetary nebulae further suggests shaping by jets.My interpretation implies that in addition to instabilities,jets also mix elements in the ejecta of core collapse supernovae.Based on the point-symmetric structure and under the assumption that jittering jets exploded this supernova,I estimate the component of the neutron star natal kick velocity on the plane of the sky to be■235 km s^(-1),and at an angle of■47°to the direction of the main jet-axis.I analyze this natal kick direction together with 12 other SNRs in the frame of the jittering jets explosion mechanism.
基金supported by the National Natural Science Foundation of China(NSFC)through grant Nos.12133002,U2031209 and 12203025Shandong Provincial Natural Science Foundation through project ZR2022QA064the CSST Milky Way and Nearby Galaxies Survey on Dust and Extinction Project CMS-CSST2021-A09。
文摘Dust extinction law is crucial to recover the intrinsic energy distribution of celestial objects and infer the characteristics of interstellar dust.Based on the traditional pair method,an improved pair method is proposed to model the dust extinguished spectral energy distribution(SED)of an individual star.Instead of the mathematically parameterizing extinction curves,the extinction curves in this work are directly from the silicate-graphite dust model,so that the dust extinction law can be obtained and the dust properties can be analyzed simultaneously.The ATLAS9 stellar model atmosphere is adopted for the intrinsic SEDs in this work,while the silicate-graphite dust model with a dust size distribution of dn da~a^(-a)exp(-a a_(c)),0.005<a<5μmfor each component is adopted for the model extinction curves.One typical extinction tracer in the dense region(V410 Anon9)and one in the diffuse region(Cyg OB2#12)of the Milky Way are chosen to test the reliability and the practicability of the improved pair method in different stellar environments.The results are consistent with their interstellar environments and are in agreement with the previous observations and studies,which prove that the improved pair method is effective and applicable in different stellar environments.In addition to the reliable extinction results,the derived parameters in the dust model can be used to analyze the dust properties,which cannot be achieved by other methods with the mathematical extinction models.With the improved pair method,the stellar parameters can also be inferred and the extinction law beyond the wavelengths of observed data can be predicted based on the dust model as well.
基金the National Natural Science Foundation of China through Grants 10533020 and 10573017
文摘We present high spatial resolution X-ray spectroscopy of the supernova remnant Cassiopeia A with the Chandra observations. The X-ray emitting region of this remnant was divided into 38 × 34 pixels of 10″× 10″ each. Spectra of 960 pixels were created and fitted with an absorbed two component non-equilibrium ionization model. From the results of the spectral analysis we obtained maps of absorbing column density, temperatures, ionization ages, and the abundances of Ne, Mg, Si, S, Ca and Fe. The Si, S and possibly Ca abundance maps show obvious jet structures, while Fe does not follow the jet but seems to be distributed perpendicular to it. The abundances of Si, S and Ca show tight correlations between one another over a range of about two dex. This suggests that they are ejecta from explosive O- burning and incomplete Si-burning. Meanwhile, the Ne abundance is well correlated with that of Mg, indicating them to be the ashes of explosive C/Ne burning. The Fe abundance is positively correlated with that of Si when the latter is lower than 3 times the solar value, and is negatively correlated when higher. We suggest that such a two phase correlation is due to the different ways in which Fe was synthesized.
基金support from DST/GITA sponsored by the India-Taiwan collaborative project fund(GITA/DST/TWN/P-76/2017)support from DST/SERB sponsored by the Extra Mural Research project(EMR/2016/003918)+1 种基金supported in part by the Higher Education Dept.of the Govt.of West Bengal,Indiasupport from the ISRO sponsored RESPOND project(ISRO/RES/2/418/17-18)fund.
文摘Galactic transient black hole candidate(BHC)MAXI J1836–194 was discovered on 2011 Aug30,by MAXI/GSC and Swift/BAT.The source activity during this outburst continued for^3 months before entering into the quiescent state.It again became active in March 2012 and continued for another^2 months.In this paper,3-25 keV RXTE/PCA spectra from the 2011 outburst and 0.5-10.0 keV Swift/XRT data during its 2012 outburst are analyzed with the two-component advective flow(TCAF)model based fits files in XSPEC.We calculate the X-ray contributions coming from jets/outflow using a newly developed method based on the deviation of the TCAF model normalization.We also study the correlation between observed radio and estimated jet X-ray fluxes.The correlation indices(b)are found to be 1.79 and 0.61,when the 7.45 GHz Very Large Array(VLA)radio flux is correlated with the total X-ray and jet X-ray fluxes in 3-25 keV range respectively.It has been found that the jet contributes in X-rays up to a maximum of 86%during its 2011 outburst.This makes the BHC MAXI J1836–194 strongly jet dominated during the initial rising phase.
基金Supported by the National Natural Science Foundation of China
文摘We present high spatial resolution X-ray spectroscopy of supernova rem- nant G292.0+1.8 made with Chandra observations. The X-ray emitting region of this remnant was divided into 25 × 25 pixels with a scale of 20" × 20" each. Spectra of 328 pixels were created and fitted with an absorbed one component non-equilibrium ionization model. With the spectral analysis results, we obtained maps of absorbing column density, temperature, ionization age and abundances for O, Ne, Mg, Si, S and Fe. The abundances of O, Ne and Mg show tight correlations between each other in the range of about two orders of magnitude, suggesting that they are all from explo- sive C/Ne burning. Meanwhile, the abundances of Si and S are also well correlated, indicating that they are the ashes of explosive O-burning or incomplete Si-burning. The Fe emission lines are not prominent in the whole remnant, and their abundance is significantly reduced, indicating that the reverse shock may not have propagated to the Fe-rich ejecta. Based on relative abundances of O, Ne, Mg, Si and Fe to Si, we suggest a progenitor mass of 25 - 30 M⊙ for this remnant.
基金supportedby the National Key R&D Program of China (No.2017YFA0402701)by the National Natural Science Foundation of China (Grant Nos. 11373026 and11433004)+2 种基金the Joint Research Fund in Astronomy(U1631237) under cooperative agreement between the National Natural Science Foundation of China and Chinese Academy of Sciencesby the Top TalentsProgram of Yunnan Province (2015HA030)by Yunnan University’s Research Innovation Fund for Graduate Students
文摘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.
基金supported by National Key R&D Program of China(2017YFA0402701)Key Research Program of Frontier Sciences of CAS(QYZDJSSW-SLH047)supports by the National Natural Science Foundation of China(Grant Nos.11503086 and 11503087)。
文摘We have conducted a large-field simultaneous survey of 12 CO,13 CO and C18O J=1-0 emission toward the Orion A giant molecular cloud(GMC)with a sky coverage of4.4 deg2 using the Purple Mountain Observatory(PMO)-13.7 m millimeter-wavelength telescope.We use the probability distribution function of the column density(N-PDF)to investigate the distribution of molecular hydrogen in the Orion A GMC.The H2 column density,derived from the 13CO emission,of the GMC is dominated by a log-normal distribution in the range from4×1021 to1.5×1023 cm-2 with excesses both at the low-density and high-density ends.The excess of the low-density end is possibly caused by an extended and low-temperature(10 K)component with velocities in the range of 5-8 km s-1.Compared with the northern sub-regions,the southern sub-regions of the Orion A GMC contain less gas with column density in NH2>1.25×1022 cm-2.The dispersions of the N-PDFs of the sub-regions are found to correlate with the evolutionary stages of the clouds across the Orion A GMC.The structure hierarchy of Orion A GMC is explored with the DENDROGRAM algorithm,and it is found that the GMC is composed of two branches.All structures except one in the tree have virial parameters less than 2,indicating self-gravity is important on the spatial scales from0.3 to4 pc.Although power-laws and departures from lognormal distributions are found at the high-density end of N-PDFs for active star-forming regions,the N-PDFs of structures in the Orion A GMC are predominantly lognormal on scales from R0.4 to 4 pc.
基金supported by the 2011 Ministry of Education doctoral academic prizesupported by the young researcher grant of National Astronomical Observatories,Chinese Academy of Sciences
文摘We have carried out observations of 12CO J=2-1 and 12CO J=3-2 to- ward the high-mass protostellar candidate IRAS 20188+3928. Compared with previ- ous observations, the 12CO J=2-1 and 12CO J=3-2 lines both have asymmetric pro- files with an absorption dip. The velocity of the absorption dip is ~ 1.0 km s-1. The spectral shape may be caused by rotation. The velocity-integrated intensity map and position-velocity diagram of the 12CO J=2-1 line present an obvious bipolar com- ponent, further verifying that this region has an outflow motion. This region is also associated with an HII region, an IRAS source, and an H20 maser. The H20 maser has the velocity of 1.1 km s-1. Compared with the components of the outflow, we find that the H20 maser is not associated with the outflow. Using the large velocity gradi- ent model, we concluded that possible averaged gas densities of the blueshifted lobe and redshifted lobe are 1.0x 105 cm-3 and 2.0x 104 cm-a, while kinetic temperatures are 26.9 K and 52.9 K, respectively. Additionally, the outflow has a higher integrated intensity ratio (Ico J=3 - 2/Ico J=2 - 1).
基金supported by the National Natural Science Foundation of China(Grant No. 10473014)
文摘We have carried out CO J=2 - 1 and CO J = 3 - 2 observations toward Tycho's supernova remnant (SNR) using the KOSMA 3m-telescope. From these observations, we identified three molecular clouds (MCs) around the SNR. The small cloud in the southwest was discovered for the first time. In the north and east, two MCs (Cloud A and Cloud B) adjacent in space display a bow-shaped morphology, and have broad emission lines, which provide some direct evidences of the SNR-MCs interaction. The MCs are revealed at-69∽-59 km s-1, coincident with Tycho's SNR. The MCs associated with Tycho's SNR have a mass of-2.13 x 10^3 Mo. Position- velocity diagrams show the two clouds to be adjacent in velocity, which means cloud- cloud collision could occur in this region. The maximum value (0.66±0.10) of the integrated CO line intensity ratio (IcoJ=3-2/Icoj=2-1) for the three MCs agrees well with the previous measurement of individual Galactic MCs, implying that the SNR shock drove into the MCs. The two MCs have a line intensity ratio gradient. The distribution of the ratio appears to indicate that the shock propagates from the southwest to the northeast.