اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدGaia-2MASS 3D maps of Galactic interstellar dust within 3 kpc
77
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Gaia data are revolutionizing our knowledge of the evolutionary history of the Milky Way. 3D maps of the interstellar dust provide complementary information and are a tool for a wide range of uses. We aimed at building 3D maps of the dust in the Local arm and surrounding regions. To do so, Gaia DR2 photometric data were combined with 2MASS measurements to derive extinction towards stars that possess accurate photometry and relative uncertainties on DR2 parallaxes smaller than 20%. We applied to the extinctions a new hierarchical inversion algorithm adapted to large datasets and to a inhomogeneous target distribution. Each step associates regularized Bayesian
قيم البحث
اقرأ أيضاً
Gaia data and stellar surveys open the way to the construction of detailed 3D maps of the Galactic interstellar (IS) dust based on the synthesis of star distances and extinctions. Reliable extinction measurements require very accurate photometric cal
ibrations. We show the first step of an iterative process linking 3D dust maps and photometric calibrations and improving them simultaneously. Our previous 3D map of nearby IS dust was used to select low reddening SDSS/APOGEE-DR14 red giants, and this database served for an empirical effective temperature- and metallicity-dependent photometric calibration in the Gaia G and 2MASS Ks bands. This calibration has been combined with Gaia G-band empirical extinction coefficients recently published, G, J and Ks photometry and APOGEE atmospheric parameters to derive the extinction of a large fraction of the survey targets. Distances were estimated independently using isochrones and the magnitude-independent extinction K(J-Ks). This new dataset has been merged with the one used for the earlier version of dust map. A new Bayesian inversion of distance-extinction pairs has been performed to produce an updated 3D map. We present several properties of the new map. Its comparison with 2D dust emission reveals that all large dust shells seen in emission at mid- and high-latitude are closer than 300pc. The updated distribution constrains the well debated, X-ray bright North Polar Spur to originate beyond 800 pc. We use the Orion region to illustrate additional details and distant clouds. On the large scale the map reveals a complex structure of the Local Arm. 2 to 3 kpc-long chains of clouds appear in planes tilted by 15 deg with respect to the Galactic plane. A series of cavities oriented along a l=60-240deg axis crosses the Arm. (http://stilism.obspm.fr)
We present new three-dimensional (3D) interstellar dust reddening maps of the Galactic plane in three colours, E(G-Ks), E(Bp-Rp) and E(H-Ks). The maps have a spatial angular resolution of 6 arcmin and covers over 7000 deg$^2$ of the Galactic plane fo
r Galactic longitude 0 deg $<$ $l$ $<$ 360 deg and latitude $|b|$ $<$ $10$ deg. The maps are constructed from robust parallax estimates from the Gaia Data Release 2 (Gaia DR2) combined with the high-quality optical photometry from the Gaia DR2 and the infrared photometry from the 2MASS and WISE surveys. We estimate the colour excesses, E(G-Ks), E(Bp-Rp) and E(H-Ks), of over 56 million stars with the machine learning algorithm Random Forest regression, using a training data set constructed from the large-scale spectroscopic surveys LAMOST, SEGUE and APOGEE. The results reveal the large-scale dust distribution in the Galactic disk, showing a number of features consistent with the earlier studies. The Galactic dust disk is clearly warped and show complex structures possibly spatially associated with the Sagittarius, Local and Perseus arms. We also provide the empirical extinction coefficients for the Gaia photometry that can be used to convert the colour excesses presented here to the line-of-sight extinction values in the Gaia photometric bands.
We present new high resolution (R>50,000) absorption measurements of the NaI doublet (5889 - 5895A) along 482 nearby sight-lines, in addition to 807 new measurements of the CaII K (3933A) absorption line. We have combined these new data with previous
ly reported measurements to produce a catalog of absorptions towards a total of 1857 early-type stars located within 800pc of the Sun. Using these data we have determined the approximate 3-dimensional spatial distribution of neutral and partly ionized interstellar gasdensity within a distance-cube of 300pc from the Sun. All newly recorded spectra were analyzed by means of a multi-component line profile-fitting program, in most cases using simultaneous fits to the line doublets. Normalized absorption profiles were fitted by varying the velocity, doppler width and column density for all intervening interstellar clouds. The resulting total column densities were then used in conjunction with the Hipparcos distances of the target stars to construct inversion maps of the 3-D spatial density distribution of the NaI and CaII bearing gas. A plot of the equivalent width of NaI versus distance reveals a wall of neutral gas at ~80pc that can be associated with the boundary wall to the central rarefied Local Cavity region. In contrast, a similar plot for the equivalent width of CaII shows no sharply increasing absorption at 80pc, but instead we observe a slowly increasing value of CaII equivalent width with increasing sight-line distance sampled.
We present the results of the hierarchical clustering analysis of the Gaia DR2 data to search for clusters, co-moving groups, and other stellar structures. The current paper builds on the sample from the previous work, extending it in distance from 1
kpc to 3 kpc, increasing the number of identified structures up to 8292. To aid in the analysis of the population properties, we developed a neural network called Auriga to robustly estimate the age, extinction, and distance of a stellar group based on the input photometry and parallaxes of the individual members. We apply Auriga to derive the properties of not only the structures found in this paper, but also previously identified open clusters. Through this work, we examine the temporal structure of the spiral arms. Specifically, we find that the Sagittarius arm has moved by >500 pc in the last 100 Myr, and the Perseus arm has been experiencing a relative lull in star formation activity over the last 25 Myr. We confirm the findings from the previous paper on the transient nature of the spiral arms, with the timescale of transition of a few 100 Myr. Finally, we find a peculiar ~1 Gyr old stream of stars that appears to be heliocentric. It is unclear what is the origin of it.
Extragalactic astronomy relies on the accurate estimation of source photometry corrected for Milky Way dust extinction. This has motivated the creation of a number of Galactic dust maps. We investigate whether these maps are contaminated by extragala
ctic signals using the clustering-redshift technique, i.e., by measuring a set of angular cross-correlations with spectroscopic objects as a function of redshift. Our tomographic analysis reveals imprints of extragalactic large-scale structure patterns in nine out of 10 Galactic dust maps, including all infrared-based maps as well as stellar reddening maps. When such maps are used for extinction corrections, this extragalactic contamination introduces redshift- and scale-dependent biases in photometric estimates at the millimagnitude level. It can affect both object-based analyses, such as the estimation of the Hubble diagram with supernovae, as well as spatial statistics. The bias can be appreciable when measuring angular correlation functions with low amplitudes, such as lensing-induced correlations or angular correlations for sources distributed over a broad redshift range. As expected, we do not detect any extragalactic contamination for the dust map inferred from 21cm HI observations. Such a map provides an alternative to widely used infrared-based maps but relies on the assumption of a constant dust-to-gas ratio. We note that, using the WISE 12 micron map sensitive to polycyclic aromatic hydrocarbons (PAH), an indirect dust tracer, we detect the diffuse extragalactic PAH background up to $zsim2$. Finally, we provide a procedure to minimize the level of biased magnitude corrections in maps with extragalactic imprints.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
