arXiv: Astrophysics of Galaxies最新文献_第9页

More insights into bar quenching 更多关于棒材淬火的见解

arXiv: Astrophysics of Galaxies Pub Date : 2020-10-07 DOI: 10.1051/0004-6361/202038810

K. George, Prajwel Joseph, C. Mondal, S. Subramanian, A. Subramaniam, K. T. Paul

{"title":"More insights into bar quenching","authors":"K. George, Prajwel Joseph, C. Mondal, S. Subramanian, A. Subramaniam, K. T. Paul","doi":"10.1051/0004-6361/202038810","DOIUrl":"https://doi.org/10.1051/0004-6361/202038810","url":null,"abstract":"The underlying nature of the process of star formation quenching in the central regions of barred disc galaxies that is due to the action of stellar bar is not fully understood. We present a multi-wavelength study of four barred galaxies using the archival data from optical, ultraviolet, infrared, CO, and HI imaging data on star formation progression and stellar and gas distribution to better understand the process of bar quenching. We found that for three galaxies, the region between the nuclear or central sub-kiloparsec region and the end of the bar (bar region) is devoid of neutral and molecular hydrogen. While the detected neutral hydrogen is very negligible, we note that molecular hydrogen is present abundantly in the nuclear or central sub-kiloparsec regions of all four galaxies. The bar co-rotation radius is also devoid of recent star formation for three out of four galaxies. One galaxy shows significant molecular hydrogen along the bar, which might mean that the gas is still being funnelled to the centre by the action of the stellar bar. Significant star formation is also present along the bar co-rotation radius of this galaxy. The study presented here supports a scenario in which gas redistribution as a result of the action of stellar bar clears the bar region of fuel for further star formation and eventually leads to star formation quenching in the bar region.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77687215","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: 7

The onset of gravothermal core collapse in velocity-dependent self-interacting dark matter subhaloes 速度依赖的自相互作用暗物质亚晕中重力热核坍缩的开始

arXiv: Astrophysics of Galaxies Pub Date : 2020-10-06 DOI: 10.1093/mnras/stab1725

Hannah C. Turner, M. Lovell, J. Zavala, M. Vogelsberger

{"title":"The onset of gravothermal core collapse in velocity-dependent self-interacting dark matter subhaloes","authors":"Hannah C. Turner, M. Lovell, J. Zavala, M. Vogelsberger","doi":"10.1093/mnras/stab1725","DOIUrl":"https://doi.org/10.1093/mnras/stab1725","url":null,"abstract":"It has been proposed that gravothermal collapse due to dark matter self-interactions (i.e. self-interacting dark matter, SIDM) can explain the observed diversity of the Milky Way (MW) satellites' central dynamical masses. We investigate the process behind this hypothesis using an $N$-body simulation of a MW-analogue halo with velocity dependent self-interacting dark matter (vdSIDM) in which the low velocity self-scattering cross-section, $sigma_rmn{T}/m_rmn{x}$, reaches 100$~$cm$^{2}$g$^{-1}$; we dub this model the vd100 model. We compare the results of this simulation to simulations of the same halo that employ different dark models, including cold dark matter (CDM) and other, less extreme SIDM models. The masses of the vd100 haloes are very similar to their CDM counterparts, but the values of their maximum circular velocities, $V_rmn{max}$, are significantly higher. We determine that these high $V_rmn{max}$ subhaloes were objects in the mass range [$5times10^{6}$, $1times10^{8}$]$~$$msun$ at $z=1$ that undergo gravothermal core collapse. These collapsed haloes have density profiles that are described by single power laws down to the resolution limit of the simulation, and the inner slope of this density profile is approximately $-3$. Resolving the ever decreasing collapsed region is challenging, and tailored simulations will be required to model the runaway instability accurately at scales $<1$$~$kpc.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84499545","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: 22

How well can we determine ages and chemical abundances from spectral fitting of integrated light spectra? 通过对综合光谱的光谱拟合，我们能在多大程度上确定年龄和化学丰度?

arXiv: Astrophysics of Galaxies Pub Date : 2020-10-06 DOI: 10.1093/mnras/staa3051

Geraldo Gonçalves, P. Coelho, R. Schiavon, C. Usher

{"title":"How well can we determine ages and chemical abundances from spectral fitting of integrated light spectra?","authors":"Geraldo Gonçalves, P. Coelho, R. Schiavon, C. Usher","doi":"10.1093/mnras/staa3051","DOIUrl":"https://doi.org/10.1093/mnras/staa3051","url":null,"abstract":"The pixel-to-pixel spectral fitting technique is often used in studies of stellar populations. It enables the user to infer several parameters from integrated light spectra such as ages and chemical abundances. In this paper, we examine the question of how the inferred parameters change with the choice of wavelength range used. We have employed two different libraries of integrated light spectra of globular clusters (GCs) from the literature and fitted them to stellar population models using the code Starlight. We performed tests using different regions of the spectra to infer reddening, ages, [Fe/H] and [alpha/Fe]. Comparing our results to age values obtained from isochrone fitting and chemical abundances from high resolution spectroscopy, we find that: (1) The inferred parameters change with the wavelength range used; (2) The method in general retrieves good reddening estimates, specially when a wider wavelength range is fitted; (3) The ideal spectral regions for determination of age, [Fe/H], and [alpha/Fe] are: 4170-5540A, 5280-7020A, and 4828-5364A, respectively; (4) The retrieved age values for old metal-poor objects can be several Gyr younger than those resulting from isochrone fitting. We conclude that, depending on the parameter of interest and the accuracy requirements, fitting the largest possible wavelength range may not necessarily be the best strategy.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86558856","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: 2

Galaxies with kinematically distinct cores in Illustris 在Illustris中具有运动上不同核心的星系

arXiv: Astrophysics of Galaxies Pub Date : 2020-10-05 DOI: 10.1051/0004-6361/202039562

I. Ebrov'a, E. Lokas, J. Eli'avsek

{"title":"Galaxies with kinematically distinct cores in Illustris","authors":"I. Ebrov'a, E. Lokas, J. Eli'avsek","doi":"10.1051/0004-6361/202039562","DOIUrl":"https://doi.org/10.1051/0004-6361/202039562","url":null,"abstract":"The growing amount of integral-field spectroscopic data creates an increased demand for understanding kinematic peculiarities that carry valuable information about the evolution of the host galaxies. For kinematically distinct cores (KDCs), a number of formation mechanisms have been proposed, but it is still unclear which of them commonly occur in the Universe. We aim to address the KDC formation in the cosmological context. We used the publicly available data of the large-scale hydrodynamic cosmological simulation Illustris. We identify 134 KDCs, study their properties, and follow their evolution back in time. Examples of four galaxies hosting KDCs are presented and described in detail. The masses of the KDC hosts follow the general distribution of the Illustris galaxies, with a possible slight preference towards massive galaxies. KDCs can be long-lived features, with their formation epochs roughly uniformly distributed in look-back times 0-11.4 Gyr, and they can survive even major or multiple subsequent mergers. There is no single channel of KDC formation, but mergers seem to be the formation mechanism for about 60% of KDCs with a significant preference for major mergers and with the percentage being higher among massive hosts. Other KDCs formed during a pericentric passage or flyby of another galaxy, by precession of a previously formed rapidly rotating core, or without an obvious external cause. The mean mass-weighted stellar age inside the KDC radius is either about the same as the look-back time of the KDC formation or older. Although the radii of our KDCs are on average larger than observed, we find that younger stellar ages are typically associated with smaller KDCs. A significant fraction of KDC hosts possess stellar shells formed during mergers that led to KDCs within the last 5 Gyr, or double peaks in their velocity dispersion maps.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89782403","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: 3

Dust and gas in the central region of NGC 1316 (Fornax A) ngc1316(天炉座A)中心区域的尘埃和气体

arXiv: Astrophysics of Galaxies Pub Date : 2020-10-04 DOI: 10.1051/0004-6361/202038150

T. Richtler, M. Hilker, E. M. D. D. Astronomia, U. Concepcion, E. Observatory, I. Capodimonte, Naples

{"title":"Dust and gas in the central region of NGC 1316 (Fornax A)","authors":"T. Richtler, M. Hilker, E. M. D. D. Astronomia, U. Concepcion, E. Observatory, I. Capodimonte, Naples","doi":"10.1051/0004-6361/202038150","DOIUrl":"https://doi.org/10.1051/0004-6361/202038150","url":null,"abstract":"The early-type galaxy NGC 1316 hosts about 10^7 solar masses of dust within a central radius of 5 kpc. These prominent dust structures are believed to have an external origin, which is also a popular interpretation for other dusty early-type galaxies. We use archival Hubble Space Telescope/ACS data to construct colour maps that delineate the dust pattern in detail, and we compare these data with maps constructed with data from MUSE of the VLT at the European Southern Observatory. Twelve MUSE pointings in wide field mode form a mosaic of the central 3.3'x2.4'. We use the tool PyParadise to fit the stellar population. We use the residual emission lines and the residual interstellar absorption NaI D-lines, and we measure line strengths, the velocity field, and the velocity dispersion field. The emission lines resemble LINER lines, with [NII] being the strongest line everywhere. Ionising sources are plausibly the post-asymptotic giant branch stars of the old or intermediate-age stellar population. There is a striking match between the dust structures, ionised gas, and atomic gas distributions, the last of which is manifested by interstellar absorption residuals of the stellar NaI D-lines. In the dust-free regions, the interstellar NaI D-lines appear in emission, which is indicative of a galactic wind. The velocity field of the ionised gas (and thus of the dust) is characterised by small-scale turbulent movements that indicate short lifetimes. At the very centre, a bipolar velocity field of the ionised gas is observed, which we interpret as an outflow. We identify a strongly inclined gaseous dusty disc along the major axis of NGC1316. A straight beam of ionised gas with a length of about 4 kpc emanates from the centre. Our findings are strongly suggestive of a dusty outflow. Nuclear outflows may be important dust-producing machines in galaxies. (Abridged)","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83941861","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

VVVX-Gaia discovery of a low luminosity globular cluster in the Milky Way disk VVVX-Gaia在银河系中发现了一个低光度球状星团

arXiv: Astrophysics of Galaxies Pub Date : 2020-10-01 DOI: 10.1051/0004-6361/202039233

E. R. Garro, D. Minniti, M. G'omez, J. Alonso-Garc'ia, R. Barb'a, B. Barbuy, J. Clari'a, A. Chen'e, B. Dias, M. Hempel, V. Ivanov, P. Lucas, D. Majaess, F. Mauro, C. M. Bidin, T. Palma, J. Pullen, R. Saito, L. Smith, F. Surot, S. R. Alegr'ia, M. Rejkuba, V. Ripepi

{"title":"VVVX-Gaia discovery of a low luminosity globular cluster in the Milky Way disk","authors":"E. R. Garro, D. Minniti, M. G'omez, J. Alonso-Garc'ia, R. Barb'a, B. Barbuy, J. Clari'a, A. Chen'e, B. Dias, M. Hempel, V. Ivanov, P. Lucas, D. Majaess, F. Mauro, C. M. Bidin, T. Palma, J. Pullen, R. Saito, L. Smith, F. Surot, S. R. Alegr'ia, M. Rejkuba, V. Ripepi","doi":"10.1051/0004-6361/202039233","DOIUrl":"https://doi.org/10.1051/0004-6361/202039233","url":null,"abstract":"Milky Way globular clusters (MW GCs) are difficult to identify at low Galactic latitudes because of high differential extinction and heavy star crowding. The new deep near-IR images and photometry from the VISTA Variables in the Via Lactea Extended Survey (VVVX) allow us to chart previously unexplored regions. Our long term aim is to complete the census of MW GCs. The immediate goals are to estimate the astrophysical parameters, measuring their reddenings, extinctions, distances, total luminosities, proper motions, sizes, metallicities and ages. We use the near-IR VVVX survey database, in combination with Gaia DR2 optical photometry, and with the Two Micron All Sky Survey (2MASS) photometry. We report the detection of a heretofore unknown Galactic Globular Cluster at $RA =$ 14:09:00.0; $DEC=-$65:37:12 (J2000). We calculate a reddening of $E(J-K_s)=(0.3pm 0.03)$ mag and an extinction of $A_{K_s}=(0.15pm 0.01)$ mag for this new GC. Its distance modulus and corresponding distance were measured as $(m-M)=(15.93pm0.03)$ mag and $D=(15.5pm1.0)$ kpc, respectively. We estimate the metallicity and age by comparison with known GCs and by fitting PARSEC and Dartmouth isochrones, finding $[Fe/H]=(-0.70pm0.2)$ dex and $t=(11.0pm1.0)$ Gyr. The mean GC PMs from Gaia are $mu_{alpha^ast}=(-4.68 pm 0.47 )$ mas $yr^{-1}$ and $mu_{delta}=(-1.34 pm 0.45)$ mas $yr^{-1}$. The total luminosity of our cluster is estimated to be $M_{Ks}=(-7.76pm 0.5)$ mag. We have found a new low-luminosity, old and metal-rich globular cluster, situated in the far side of the Galactic disk, at $R_{G}=11.2$ kpc from the Galactic centre, and at $z=1.0$ kpc below the plane. Interestingly, the location, metallicity and age of this globular cluster are coincident with the Monoceros Ring (MRi) structure.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73423846","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: 3

A new high-precision strong lensing model of the galaxy cluster MACS J0416.1−2403 星系团MACS J0416.1−2403的高精度强透镜模型

arXiv: Astrophysics of Galaxies Pub Date : 2020-09-30 DOI: 10.1051/0004-6361/202039564

P. Bergamini, P. Rosati, E. Vanzella, G. Caminha, C. Grillo, A. Mercurio, M. Meneghetti, G. Angora, F. Calura, M. Nonino, P. Tozzi

{"title":"A new high-precision strong lensing model of the galaxy cluster MACS J0416.1−2403","authors":"P. Bergamini, P. Rosati, E. Vanzella, G. Caminha, C. Grillo, A. Mercurio, M. Meneghetti, G. Angora, F. Calura, M. Nonino, P. Tozzi","doi":"10.1051/0004-6361/202039564","DOIUrl":"https://doi.org/10.1051/0004-6361/202039564","url":null,"abstract":"We present a new high-precision parametric strong lensing model of the galaxy cluster MACS J0416.1-2403, at z=0.396, which takes advantage of the MUSE Deep Lensed Field (MDLF, Vanzella et al. 2020b), with 17.1h integration in the North-East region of the cluster, and Hubble Frontier Fields data. We spectroscopically identify 182 multiple images from 48 background sources at 0.9<z<6.2, and 171 cluster member galaxies. Several multiple images are associated to individual clumps in multiply lensed resolved sources. By defining a new metric, which is sensitive to the gradients of the deflection field, we show that we can accurately reproduce the positions of these star-forming knots despite their vicinity to the model critical lines. The high signal-to-noise spectra of the MDLF enables the measurement of the internal velocity dispersion of 64 cluster galaxies, down to m(F160W)=22. This allows us to independently estimate the contribution of the subhalo mass component of the lens model from the measured Faber-Jackson scaling relation. Our best reference model, which represents a significant step forward compared to our previous analyses, is selected from a comparative study of different mass parametrizations. The r.m.s. displacement between the observed and model-predicted image positions is only 0.40\", 33% smaller than in all previous models. The mass model appears to be particularly well constrained in the MDLF region. We characterize the robustness of the magnification map at varying distances from the model critical lines and the total projected mass profile of the cluster.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84662874","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: 9

Dorado and its member galaxies 多拉多及其成员星系

arXiv: Astrophysics of Galaxies Pub Date : 2020-09-30 DOI: 10.1051/0004-6361/202038996

R. Rampazzo, S. Ciroi, Paola Mazzei, F. D. Mille, E. Congiu, A. Cattapan, L. Bianchi, E. Iodice, A. Marino, H. Plana, J. Postma, M. Spavone

{"title":"Dorado and its member galaxies","authors":"R. Rampazzo, S. Ciroi, Paola Mazzei, F. D. Mille, E. Congiu, A. Cattapan, L. Bianchi, E. Iodice, A. Marino, H. Plana, J. Postma, M. Spavone","doi":"10.1051/0004-6361/202038996","DOIUrl":"https://doi.org/10.1051/0004-6361/202038996","url":null,"abstract":"ABRIDGED: Dorado is a nearby, rich and clumpy galaxy group that extends for several degrees in the Southern Hemisphere. For the first time, we map the Ha distribution as a possible indicator of star formation (SF) activity of Dorado members a large fraction of which show interaction and merging signatures. With the 2.5m du Pont and the 1m Swope telescopes we obtained narrow-band, calibrated images of 14 galaxies, forming the backbone of the group, mapping Ha+[N II] down to few 10$^{-17}$ erg~cm$^{-2}$~s$^{-1}$~arcsec$^{-2}$. We estimated the galaxy star formation rate (SFR) from the Ha fluxes, corrected for Galaxy foreground extinction and [N II] contamination. Ha+[N II] emission has been detected in all galaxies. HII regions clearly emerge in late-type galaxies (LTGs) , while in early-type galaxies (ETGs) the Ha+[N II] emission is dominated by [N II], especially in the central regions. However, HII complexes are also revealed in four ETGs. Considering the Dorado group as a whole, we notice that the Ha+[N II] equivalent width, a measure of the specific SF, increases with the morphological type, from early to late-type members, although it remains lower that what observed in similar surveys of spiral galaxies. The SFR of the spiral members is in the range of what observed in similar galaxies surveys James+ (2004), although, in three spirals the SFR is well below the median for their morphological classes. The SFR of some early-type members tends, at odds, to be higher than the average derived from Ha+[N II] surveys of this morphological family. We detected in Ha+[N II] all the ETGs observed and half of them show HII regions. These findings suggest that ETGs in this group are not dead galaxies: their SF has not shut down yet. Mechanisms such as gas stripping and gas accretion, through galaxy-galaxy interaction, seem relevant in modifying the SF in this evolutionary phase of Dorado.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89956227","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: 2

Exploring the origin of low-metallicity stars in Milky-Way-like galaxies with the NIHAO-UHD simulations 利用NIHAO-UHD模拟探索类银河系星系中低金属丰度恒星的起源

arXiv: Astrophysics of Galaxies Pub Date : 2020-09-29 DOI: 10.1093/mnras/staa3479

F. Sestito, T. Buck, E. Starkenburg, N. Martin, J. Navarro, K. Venn, A. Obreja, P. Jablonka, A. Macciò

{"title":"Exploring the origin of low-metallicity stars in Milky-Way-like galaxies with the NIHAO-UHD simulations","authors":"F. Sestito, T. Buck, E. Starkenburg, N. Martin, J. Navarro, K. Venn, A. Obreja, P. Jablonka, A. Macciò","doi":"10.1093/mnras/staa3479","DOIUrl":"https://doi.org/10.1093/mnras/staa3479","url":null,"abstract":"The kinematics of the most metal-poor stars provide a window into the early formation and accretion history of the Milky Way. Here, we use 5~high-resolution cosmological zoom-in simulations ($sim~5times10^6$ star particles) of Milky Way-like galaxies taken from the NIHAO-UHD project, to investigate the origin of low-metallicity stars ([Fe/H]$leq-2.5$). The simulations show a prominent population of low-metallicity stars confined to the disk plane, as recently discovered in the Milky Way. The ubiquity of this finding suggests that the Milky Way is not unique in this respect. Independently of the accretion history, we find that $gtrsim~90$ per cent of the retrograde stars in this population are brought in during the initial build-up of the galaxies during the first few Gyrs after the Big Bang. Our results therefore highlight the great potential of the retrograde population as a tracer of the early build-up of the Milky Way. The prograde planar population, on the other hand, is accreted during the later assembly phase and samples the full galactic accretion history. In case of a quiet accretion history, this prograde population is mainly brought in during the first half of cosmic evolution ($tlesssim7$~Gyr), while, in the case of an on-going active accretion history, later mergers on prograde orbits are also able to contribute to this population. Finally, we note that the Milky Way shows a rather large population of eccentric, very metal-poor planar stars. This is a feature not seen in most of our simulations, with the exception of one simulation with an exceptionally active early building phase.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78361884","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: 13

Dust emission, extinction, and scattering in LDN 1642 ldn1642的尘埃发射、消光和散射

arXiv: Astrophysics of Galaxies Pub Date : 2020-09-26 DOI: 10.1051/0004-6361/202038611

M. Juvela, S. Neha, E. Mannfors, M. Saajasto, N. Ysard, V. Pelkonen

{"title":"Dust emission, extinction, and scattering in LDN 1642","authors":"M. Juvela, S. Neha, E. Mannfors, M. Saajasto, N. Ysard, V. Pelkonen","doi":"10.1051/0004-6361/202038611","DOIUrl":"https://doi.org/10.1051/0004-6361/202038611","url":null,"abstract":"We study the near-infrared (NIR) scattering in LDN 1642, its correlation with the cloud structure, and the ability of dust models to simultaneously explain sub-millimetre emission, NIR extinction, and NIR scattering. \u0000We use observations from the HAWK-I instrument to measure the NIR surface brightness and extinction. These are compared with Herschel data on dust emission and, with radiative transfer modelling, with predictions calculated for different dust models. \u0000We find an optical depth ratio $tau(250,mu{rm m})/tau(J)approx 10^{-3}$, confirming earlier findings of high sub-millimetre emissivity. The relationships between the column density derived from dust emission and the NIR colour excesses is linear and consistent with the standard NIR extinction curve. The extinction peaks at $A_J=2.6,$mag, the NIR surface brightness remaining correlated with $N({rm H}_2)$ without saturation. \u0000Radiative transfer models can fit the sub-millimetre data with any of the tested dust models. However, these predict a NIR extinction that is higher and a NIR surface brightness that is lower than in observations. If the dust sub-millimetre emissivity is rescaled to the observed value of $tau(250,mu{rm m})/tau(J)$, dust models with high NIR albedo can reach the observed level of NIR surface brightness. The NIR extinction of the models tends to be higher than directly measured, which is reflected in the shape of the NIR surface brightness spectra. \u0000The combination of emission, extinction, and scattering measurements provides strong constraints on dust models. The observations of LDN 1642 indicate clear dust evolution, including a strong increase in the sub-millimetre emissivity, not yet fully explained by the current dust models.","PeriodicalId":8452,"journal":{"name":"arXiv: Astrophysics of Galaxies","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83203772","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