arXiv: Astrophysics of Galaxies最新文献_第10页

Ammonia observations towards the Aquila Rift cloud complex 对天鹰座裂谷云复合体的氨观测

arXiv: Astrophysics of Galaxies Pub Date : 2020-09-25 DOI: 10.1051/0004-6361/202037659

K. Tursun, J. Esimbek, C. Henkel, Xindi Tang, Gang Wu, Da-lei Li, Jianjun Zhou, Yuxin He, T. Komesh, S. Sailanbek

{"title":"Ammonia observations towards the Aquila Rift cloud complex","authors":"K. Tursun, J. Esimbek, C. Henkel, Xindi Tang, Gang Wu, Da-lei Li, Jianjun Zhou, Yuxin He, T. Komesh, S. Sailanbek","doi":"10.1051/0004-6361/202037659","DOIUrl":"https://doi.org/10.1051/0004-6361/202037659","url":null,"abstract":"We surveyed the Aquila Rift complex including the Serpens South and W40 region in the NH$_3$(1,1) and (2,2) transitions making use of the Nanshan 26-m telescope. The kinetic temperatures of the dense gas in the Aquila Rift complex range from 8.9 to 35.0K with an average of 15.3$pm$6.1K. Low gas temperatures associate with Serpens South ranging from 8.9 to 16.8K with an average 12.3$pm$1.7K, while dense gas in the W40 region shows higher temperatures ranging from 17.7 to 35.0K with an average of 25.1$pm$4.9 K. A comparison of kinetic temperatures against HiGal dust temperatures indicates that the gas and dust temperatures are in agreement in the low mass star formation region of Serpens South. In the high mass star formation region W40, the measured gas kinetic temperatures are higher than those of the dust. The turbulent component of the velocity dispersion of NH$_3$(1,1) is found to be positively correlated with the gas kinetic temperature, which indicates that the dense gas may be heated by dissipation of turbulent energy. For the fractional total-NH3 abundance obtained by a comparison with Herschel infrared continuum data representing dust emission we find values from 0.1 to 21$times 10^{-8}$ with an average of 6.9$(pm 4.5)times 10^{-8}$. Serpens South also shows a fractional total-NH3 abundance ranging from 0.2 to 21$times 10^{-8}$ with an average of 8.6($pm 3.8)times 10^{-8}$. In W40, values are lower, between 0.1 and 4.3$times 10^{-8}$ with an average of 1.6($pm 1.4)times 10^{-8}$. Weak velocity gradients demonstrate that the rotational energy is a negligible fraction of the gravitational energy. In W40, gas and dust temperatures are not strongly dependent on the projected distance to the recently formed massive stars. Overall, the morphology of the mapped region is ring-like, with strong emission at lower and weak emission at higher Galactic longitudes.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79434506","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Spatially Resolved Kinematics of gas and stars in hidden type 1 AGNs 隐藏型agn中气体和恒星的空间分辨运动学

arXiv: Astrophysics of Galaxies Pub Date : 2020-09-24 DOI: 10.5303/JKAS.2020.53.5.103

D. Son, J. Woo, Da-in Eun, Hojin Cho, M. Karouzos, S. Park

{"title":"Spatially Resolved Kinematics of gas and stars in hidden type 1 AGNs","authors":"D. Son, J. Woo, Da-in Eun, Hojin Cho, M. Karouzos, S. Park","doi":"10.5303/JKAS.2020.53.5.103","DOIUrl":"https://doi.org/10.5303/JKAS.2020.53.5.103","url":null,"abstract":"We present the spatially resolved gas and stellar kinematics of a sample of ten hidden type 1 AGNs in order to investigate the true nature of the central source and the scaling relation with host galaxy stellar velocity dispersion. The sample is selected from a large number of hidden type 1 AGN, which are identified based on the presence of a broad component in the ha line profile (i.e., full-width-at-half-maximum $>$ $sim$1000 kms), while they are often mis-classified as type 2 AGN because AGN continuum and broad emission lines are weak or obscured in the optical spectral range. We used the Blue Channel Spectrograph at the 6.5-m MMT (Multiple Mirror Telescope) to obtain long-slit data. We detected a broad hb for only two targets, however, the presence of a strong broad ha indicates that these AGNs are low-luminosity type 1 AGNs. We measured the velocity, velocity dispersion and flux of stellar continuum and gas emission lines (i.e., hb and oiii) as a function of distance from the center with a spatial scale of 0.3 arcsec pixel$^{-1}$. Spatially resolved gas kinematics traced by hb or oiii are generally similar to stellar kinematics except for the very center, where signatures of gas outflows are detected. We compare the luminosity-weighted effective stellar velocity dispersion with black hole mass, finding that these hidden type 1 AGN with relatively low back hole mass follow the scaling relation of the reverberation-mapped type 1 AGN and more massive inactive galaxies. }","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91444685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Decoding Starlight with Big Survey Data, Machine Learning, and Cosmological Simulations 解码星光与大调查数据，机器学习和宇宙模拟

arXiv: Astrophysics of Galaxies Pub Date : 2020-09-22 DOI: 10.7916/D8-BWAR-S896

K. Blancato

{"title":"Decoding Starlight with Big Survey Data, Machine Learning, and Cosmological Simulations","authors":"K. Blancato","doi":"10.7916/D8-BWAR-S896","DOIUrl":"https://doi.org/10.7916/D8-BWAR-S896","url":null,"abstract":"Stars, and collections of stars, encode rich signatures of stellar physics and galaxy evolution. With properties influenced by both their environment and intrinsic nature, stars retain information about astrophysical phenomena that are not otherwise directly observable. In the time-domain, the observed brightness variability of a star can be used to investigate physical processes occurring at the stellar surface and in the stellar interior. On a galactic scale, the properties of stars, including chemical abundances and stellar ages, serve as a multi-dimensional record of the origin of the galaxy. In the Milky Way, together with orbital properties, this informs the details of the evolution of our Galaxy since its formation. Extending beyond the Local Group, the attributes of unresolved stellar populations allow us to study the diversity of galaxies in the Universe. \u0000By examining the properties of stars, and how they vary across a range of spatial and temporal scales, this Dissertation connects the information residing within stars to global processes in galactic formation and evolution. We develop new approaches to determine stellar properties, including rotation and surface gravity, from the variability that we directly observe. We offer new insight into the chemical enrichment history of the Milky Way, tracing different stellar explosions that capture billions of years of evolution. We advance knowledge and understanding of how stars and galaxies are linked, by examining differences in the initial stellar mass distributions comprising galaxies, as they form. In building up this knowledge, we highlight current tensions between data and theory. By synthesizing numerical simulations, large observational data sets, and machine learning techniques, this work makes valuable methodological contributions to maximize insights from diverse ensembles of current and future stellar observations.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86076907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Tango for three: Sagittarius, LMC, and the Milky Way 三人探戈:人马座、LMC和银河系

arXiv: Astrophysics of Galaxies Pub Date : 2020-09-22 DOI: 10.1093/mnras/staa3673

E. Vasiliev, V. Belokurov, D. Erkal

{"title":"Tango for three: Sagittarius, LMC, and the Milky Way","authors":"E. Vasiliev, V. Belokurov, D. Erkal","doi":"10.1093/mnras/staa3673","DOIUrl":"https://doi.org/10.1093/mnras/staa3673","url":null,"abstract":"We assemble a catalogue of candidate Sagittarius stream members with 5d and 6d phase-space information, using astrometric data from Gaia DR2, distances estimated from RR Lyrae stars, and line-of-sight velocities from various spectroscopic surveys. We find a clear misalignment between the stream track and the direction of the reflex-corrected proper motions in the leading arm of the stream, which we interpret as a signature of a time-dependent perturbation of the gravitational potential. A likely cause of this perturbation is the recent passage of the most massive Milky Way satellite - the Large Magellanic Cloud (LMC). We develop novel methods for simulating the Sagittarius stream in the presence of the LMC, using specially tailored N-body simulations and a flexible parametrization of the Milky Way halo density profile. We find that while models without the LMC can fit most stream features rather well, they fail to reproduce the misalignment and overestimate the distance to the leading arm apocentre. On the other hand, models with an LMC mass in the range (1-1.7)x10^11 Msun rectify these deficiencies. We demonstrate that the stream can not be modelled adequately in a static Milky Way. Instead, our Galaxy is required to lurch toward the massive in-falling Cloud, giving the Sgr stream its peculiar shape and kinematics. By exploring the parameter space of Milky Way potentials, we determine the enclosed mass within 100 kpc to be (5.2-6.0)x10^11 Msun, and find tentative evidence for a radially-varying shape and orientation of the Galactic halo.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85659804","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 60

A new channel to form IMBHs throughout cosmic time 在宇宙时间内形成黑洞的新通道

arXiv: Astrophysics of Galaxies Pub Date : 2020-09-19 DOI: 10.1093/mnras/staa3724

P. Natarajan

{"title":"A new channel to form IMBHs throughout cosmic time","authors":"P. Natarajan","doi":"10.1093/mnras/staa3724","DOIUrl":"https://doi.org/10.1093/mnras/staa3724","url":null,"abstract":"While the formation of the first black holes at high redshift is reasonably well understood though debated, massive black hole formation at later cosmic epochs has not been adequately explored. We present a gas accretion driven mechanism that can build up black hole masses rapidly in dense, gas-rich nuclear star clusters (NSCs). Wind-fed supra-exponential accretion of an initially wandering black hole in NSCs can lead to extremely fast growth, scaling stellar mass remnant seed black holes up to intermediate mass black holes (IMBHs). Operating throughout cosmic time, growth via this new channel is modulated by the gas supply, and premature termination results in the formation of lower mass black holes with masses in the range of 50 - few 100 solar masses, filling in the so-called mass gap. However, in most gas-rich NSCs, growth is unimpeded, inevitably leading to the formation of IMBHs with masses ranging from 100 - 100,000 solar masses. A spate of new detection spanning the full range of the IMBH mass function - from the LIGO-VIRGO source GW190521 to the emerging population of 10^5 solar mass black holes harbored in low-mass dwarf galaxies - are revealing this elusive population. Naturally accounting for the detected presence of off-center IMBHs in low-mass dwarfs, this new pathway also predicts the existence of an extensive population of wandering non-central black holes in more massive galaxies would be detectable via tidal disruption events and as GW sources. Gas-rich NSCs serve as incubators for the continual formation of black holes over a wide range in mass throughout cosmic time.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90474833","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 30

The Herschel SPIRE Fourier Transform Spectrometer Spectral Feature Finder – V. Rotational measurements of NGC 891 赫歇尔尖塔傅里叶变换光谱仪光谱特征查找器- V. ngc891的旋转测量

arXiv: Astrophysics of Galaxies Pub Date : 2020-09-18 DOI: 10.1093/mnras/staa3448

C. Benson, L. Spencer, I. Valtchanov, J. Scott, N. Hładczuk

引用次数: 0

MAMMOTH: confirmation of two massive galaxy overdensities at z = 2.24 with Hα emitters 猛犸:证实了两个大质量星系在z = 2.24处的超高密度

arXiv: Astrophysics of Galaxies Pub Date : 2020-09-17 DOI: 10.1093/mnras/staa2882

Xianzhong Zheng, Z. Cai, F. An, Xiaohui Fan, Dongdong Shi

{"title":"MAMMOTH: confirmation of two massive galaxy overdensities at z = 2.24 with Hα emitters","authors":"Xianzhong Zheng, Z. Cai, F. An, Xiaohui Fan, Dongdong Shi","doi":"10.1093/mnras/staa2882","DOIUrl":"https://doi.org/10.1093/mnras/staa2882","url":null,"abstract":"Massive galaxy overdensities at the peak epoch of cosmic star formation provide ideal testbeds for the formation theories of galaxies and large-scale structure. We report the confirmation of two massive galaxy overdensities at $z=2.24$, BOSS1244 and BOSS1542, selected from the MAMMOTH project using Ly$alpha$ absorption from the intergalactic medium over the scales of 15$-$30 $h^{-1}$ Mpc imprinted on the quasar spectra. We use H$alpha$ emitters (HAEs) as the density tracer and identify them using deep narrowband $H_2S1$ and broadband $K_{rm s}$ imaging data obtained with CFHT/WIRCam. In total, 244 and 223 line emitters are detected in these two fields, and $196pm 2$ and $175pm 2$ are expected to be HAEs with an H$alpha$ flux of $> 2.5times 10^{-17}$ erg s$^{-1}$ cm$^{-2}$ (corresponding to an SFR of $>$5 M$_odot$ yr$^{-1}$). The detection rate of HAE candidates suggests an overdensity factor of $delta_{rm gal}=5.6pm0.3$ and $4.9pm0.3$ over the volume of $54times32times32$ cMpc$^3$. The overdensity factor increases $2-3$ times when focusing on the high-density regions of scales $10-15$ cMpc. Interestingly, the HAE density maps reveal that BOSS1244 contains a dominant structure, while BOSS1542 manifests as a giant filamentary structure. We measure the H$alpha$ luminosity functions (HLF), finding that BOSS1244's HLF is nearly identical to that of the general field at the same epoch, while BOSS1542 shows an excess of HAEs with high H$alpha$ luminosity, indicating the presence of enhanced star formation or AGN activity. We conclude that the two massive MAMMOTH overdensities are undergoing a rapid galaxy mass assembly.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87922596","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 8

The MOSDEF Survey: The Evolution of the Mass-Metallicity Relation from $z=0$ to $zsim3.3$. MOSDEF调查:从$z=0$到$zsim3.3$的质量-金属丰度关系演变。

arXiv: Astrophysics of Galaxies Pub Date : 2020-09-15 DOI: 10.3847/1538-4357/ABF4C1

R. Sanders, A. Shapley, T. Jones, N. Reddy, M. Kriek, B. Siana, A. Coil, B. Mobasher, I. Shivaei, R. Davé, Mojegan Azadi, S. Price, G. Leung, W. Freeman, T. Fetherolf, L. D. Groot, T. Zick, G. Barro

{"title":"The MOSDEF Survey: The Evolution of the Mass-Metallicity Relation from $z=0$ to $zsim3.3$.","authors":"R. Sanders, A. Shapley, T. Jones, N. Reddy, M. Kriek, B. Siana, A. Coil, B. Mobasher, I. Shivaei, R. Davé, Mojegan Azadi, S. Price, G. Leung, W. Freeman, T. Fetherolf, L. D. Groot, T. Zick, G. Barro","doi":"10.3847/1538-4357/ABF4C1","DOIUrl":"https://doi.org/10.3847/1538-4357/ABF4C1","url":null,"abstract":"We investigate the evolution of galaxy gas-phase metallicity (O/H) over the range $z=0-3.3$ using samples of $sim300$ galaxies at $zsim2.3$ and $sim150$ galaxies at $zsim3.3$ from the MOSDEF survey. This analysis crucially utilizes different metallicity calibrations at $zsim0$ and $z>1$ to account for evolving ISM conditions. We find significant correlations between O/H and stellar mass ($M_*$) at $zsim2.3$ and $zsim3.3$. The low-mass power law slope of the mass-metallicity relation is remarkably invariant over $z=0-3.3$, such that $textrm{O/H}propto M_*^{0.30}$ at all redshifts in this range. At fixed $M_*$, O/H decreases with increasing redshift as dlog(O/H)/d$z=-0.11pm0.02$. We find no evidence that the fundamental metallicity relation between $M_*$, O/H, and star-formation rate (SFR) evolves out to $zsim3.3$, with galaxies at $zsim2.3-3.3$ having O/H within 0.04~dex of local galaxies matched in $M_*$ and SFR on average. We employ analytic chemical evolution models to place constraints on the mass and metal loading factors of galactic outflows. The efficiency of metal removal increases toward lower $M_*$ at fixed redshift, and toward higher redshift at fixed $M_*$. These models suggest that the slope of the mass-metallicity relation is set by the scaling of the metal loading factor of outflows with $M_*$, not by the change in gas fraction as a function of $M_*$. The evolution toward lower O/H at fixed $M_*$ with increasing redshift is driven by both higher gas fraction (leading to stronger dilution of ISM metals) and higher metal removal efficiency, with models suggesting that both effects contribute approximately equally to the observed evolution. These results suggest that the processes governing the smooth baryonic growth of galaxies via gas flows and star formation hold in the same form over at least the past 12~Gyr.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87955287","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 49

A comparative study of satellite galaxies in Milky Way-like galaxies from HSC, DECaLS, and SDSS 来自HSC、DECaLS和SDSS的类银河系星系中卫星星系的比较研究

arXiv: Astrophysics of Galaxies Pub Date : 2020-09-15 DOI: 10.1093/mnras/staa3495

Wenting Wang, M. Takada, Xiangchong Li, S. Carlsten, Ting-Wen Lan, Jingjing Shi, H. Miyatake, S. More, R. Beaton, R. Lupton, Yen-Ting Lin, Tian Qiu, Wentao Luo

{"title":"A comparative study of satellite galaxies in Milky Way-like galaxies from HSC, DECaLS, and SDSS","authors":"Wenting Wang, M. Takada, Xiangchong Li, S. Carlsten, Ting-Wen Lan, Jingjing Shi, H. Miyatake, S. More, R. Beaton, R. Lupton, Yen-Ting Lin, Tian Qiu, Wentao Luo","doi":"10.1093/mnras/staa3495","DOIUrl":"https://doi.org/10.1093/mnras/staa3495","url":null,"abstract":"We conduct a comprehensive and statistical study of the luminosity functions (LFs) for satellite galaxies, by counting photometric galaxies from HSC, DECaLS and SDSS around isolated central galaxies (ICGs) and galaxy pairs from the SDSS/DR7 spectroscopic sample. Results of different surveys show very good agreement. The satellite LFs can be measured down to $M_Vsim-10$, and for central primary galaxies as small as $8.5<log_{10}M_ast/M_odot<9.2$ and $9.2<log_{10}M_ast/M_odot<9.9$, which implies there are on average 3--8 satellites with $M_V<-10$ around LMC-mass ICGs. The bright end cutoff of satellite LFs and the satellite abundance are both sensitive to the magnitude gap between the primary and its companions, indicating galaxy systems with larger magnitude gaps are on average hosted by less massive dark matter haloes. By selecting primaries with stellar mass similar to our MW, we discovered that i) the averaged satellite LFs of ICGs with different magnitude gaps to their companions and of galaxy pairs with different colour or colour combinations all show steeper slopes than the MW satellite LF; ii) there are more satellites with $-15<M_V<-10$ than those in our MW; iii) there are on average 1.5 to 2.5 satellites with $M_V<-16$ around ICGs, consistent with our MW. Thus the MW and its satellite system are atypical of our sample of MW-mass systems. In consequence, our MW is not a good representative of other MW-mass galaxies. Strong cosmological implications based on only MW satellites await additional discoveries of fainter satellites in extra-galactic systems. Interestingly, the MW satellite LF is typical among other MW-mass systems within 40~Mpc in the local Universe, perhaps implying the Local Volume is an under-dense region.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89381644","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 16

Depletion and fractionation of nitrogen in collapsing cores 崩塌岩心中氮的耗竭和分馏

arXiv: Astrophysics of Galaxies Pub Date : 2020-09-14 DOI: 10.1051/0004-6361/202038780

P. Hily-Blant, G. Pineau des Forêts, A. Faure, D. Flower

{"title":"Depletion and fractionation of nitrogen in collapsing cores","authors":"P. Hily-Blant, G. Pineau des Forêts, A. Faure, D. Flower","doi":"10.1051/0004-6361/202038780","DOIUrl":"https://doi.org/10.1051/0004-6361/202038780","url":null,"abstract":"Measurements of the nitrogen isotopic ratio in Solar System comets show a constant value, ~140, which is three times lower than the protosolar ratio, a highly significant difference that remains unexplained. Observations of static starless cores at early stages of collapse confirm the theoretical expectation that nitrogen fractionation in interstellar conditions is marginal for most species. Yet, observed isotopic ratios in N2H+ are at variance with model predictions. These gaps in our understanding of how the isotopic reservoirs of nitrogen evolve, from interstellar clouds to comets, and, more generally, to protosolar nebulae, may have their origin in missing processes or misconceptions in the chemistry of interstellar nitrogen. So far, theoretical studies of nitrogen fractionation in starless cores have addressed the quasi-static phase of their evolution such that the effect of dynamical collapse on the isotopic ratio is not known. In this paper, we investigate the fractionation of 14N and 15N during the gravitational collapse of a pre-stellar core through gas-phase and grain adsorption and desorption reactions. The initial chemical conditions, which are obtained in steady state after typically a few Myr, show low degrees of fractionation in the gas phase, in agreement with earlier studies. However, during collapse, the differential rate of adsorption of 14N- and 15N-containing species onto grains results in enhanced 15N:14N ratios, in better agreement with the observations. Furthermore, we find differences in the behavior, with increasing density, of the isotopic ratio in different species. We find that the collapse must take place on approximately one free-fall timescale, based on the CO abundance profile in L183 [see the end in the PDF file]","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91526755","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 6