arXiv subjects

Shuaibo Bian

Publications and source records attributed to Shuaibo Bian.

8 recordsLinked to original sources

arXiv2026

East Asian VLBI Network astrometry toward the star-forming region G040.96+02.48 in the Extreme Outer Galaxy

Accurate astrometric measurements for star-forming regions located on the far side of the Milky Way remain scarce. In this work, we present the astrometric results for a 22\,GHz water maser associated with star-forming region G040.96+02.48 located on the far side of the Milky Way, using the East Asian VLBI Network. The target water maser's proper motion was determined to be ($μ_α\cosδ, μ_δ$) = ($-2.06_{-0.51}^{+0.53}$, $-2.95_{-0.44}^{+0.45}$)~mas~yr$^{-1}$. The derived three-dimensional kinematic distance to the star-forming region is 20.2$\pm$3.2\,kpc, placing it slightly outside the Outer Scutum$-$Centaurus Arm. The corresponding vertical height of 872$\pm$139\,pc indicates a significant warp of the outer Galactic disk, which is in good agreement with the latest precessing warp model. Moreover, the resulting peculiar motions reveal a complex kinematic pattern, characterized by a large outward radial velocity of $-32\pm$18\,km~s$^{-1}$. Our observations substantially expand the valuable sample of star-forming regions with accurate astrometric measurements in the Extreme Outer Galaxy.

astro-ph.GA↗

arXiv2024

A New Statistical Analysis of the Morphology of Spiral Galaxies

Morphology is the starting point for understanding galaxies. Elmegreen et al. classified spiral galaxies into flocculent, multiple-arm, and grand-design galaxies based on the regularity of their spiral arm structure. With the release of a vast number of clear spiral galaxy images from the Sloan Digital Sky Survey, we conducted a morphological classification of 5093 blue spiral galaxies. A statistical analysis of this sample shows that the fractions of flocculent, multiple-arm, and grand-design galaxies are 38 $\pm$ 1%, 59 $\pm$ 1%, and 3 $\pm$ 1%, respectively. Redshift has no obvious influence on this classification. However, as the bulge size becomes larger, the fraction of multiple-arm galaxies increases, while that of flocculent galaxies decreases. In addition, we performed a statistical analysis of 3958 galaxies with a clear spiral arm structure, finding 82% of these galaxies have two arms in their inner regions. We also found that the majority (74%) of the barred spiral galaxies exhibit the characteristics of two inner spiral arms and multiple outer spiral arms, and there is no barred spiral galaxy in this work with four continuous spiral arms from the inner to the outer regions. These results highlight that the spiral arm structure of the Milky Way, according to the current mainstream view of a four-arm galaxy with continuous arms extending from the inner to outer regions, is quite unique. However, our findings align with the spiral morphology of the Milky Way proposed by Xu et al., in which case our Galaxy can be considered typical.

astro-ph.GA↗

arXiv2024

VLBI with SKA: Possible Arrays and Astrometric Science

The next generation of very long baseline interferometry (VLBI) is stepping into the era of microarcsecond ($μ$as) astronomy, and pushing astronomy, especially astrometry, to new heights. VLBI with the Square Kilometre Array (SKA), SKA-VLBI, will increase current sensitivity by an order of magnitude, and reach astrometric precision routinely below 10 $μ$as, even challenging 1 $μ$as. This advancement allows precise parallax and proper motion measurements of various celestial objects. Such improvements can be used to study objects (including isolated objects, and binary or multiple systems) in different stellar stages (such as star formation, main-sequence stars, asymptotic giant branch stars, pulsars, black holes, white dwarfs, etc.), unveil the structure and evolution of complex systems (such as the Milky Way), benchmark the international celestial reference frame, and reveal cosmic expansion. Furthermore, the theory of general relativity can also be tested with SKA-VLBI using precise measurements of light deflection under the gravitational fields of different solar system objects and the perihelion precession of solar system objects.

astro-ph.GA↗

arXiv2024

Molecular Bubble and Outflow in S Mon Revealed by Multiband Datasets

We identify a molecular bubble, and study the star formation and its feedback in the S Mon region, using multiple molecular lines, young stellar objects (YSOs), and infrared data. We revisit the distance to S Mon, ~722+/-9 pc, using Gaia Data Release 3 parallaxes of the associated Class II YSOs. The bubble may be mainly driven by a massive binary system (namely 15 Mon), the primary of which is an O7V-type star. An outflow is detected in the shell of the bubble, suggesting ongoing star formation activities in the vicinity of the bubble. The total wind energy of the massive binary star is three orders of magnitude higher than the sum of the observed turbulent energy in the molecular gas and the kinetic energy of the bubble, indicating that stellar winds help to maintain the turbulence in the S Mon region and drive the bubble. We conclude that the stellar winds of massive stars have an impact on their surrounding environment.

astro-ph.GA↗

arXiv2023

Kinematics of the Local Spiral Structure Revealed by Young Stars in \emph{Gaia}~DR3

Using young open clusters and O--B2-type stars in~\emph{Gaia}~DR3, we investigate the kinematics of the local spiral structure. In general, the young sources in the outer spiral arms may present larger peculiar motions than those in the inner spiral arms. The young open clusters appear to have smaller peculiar motions than the O--B2-type stars, and the sources in both the Perseus and Local Arms may show an inward motion toward the Galactic center and rotate slower than Galactic rotation. Meanwhile, the sources in the Carina Arm may move in the opposite direction from the Sun to the Galactic center and rotate marginally faster than Galactic rotation. In addition, using young open clusters and O--B2-type stars, we have improved the distance estimations of kinematic methods for several regions near the Sun.

astro-ph.GA↗

arXiv2023

Distributions and Physical Properties of Molecular Clouds in the Third Galactic Quadrant: $l$ = [219.75, 229.75]$^\circ$ and $b$ = [-5.25, 5.25]$^\circ$

We present the results of an unbiased $^{12}$CO/$^{13}$CO/C$^{18}$O ($J$ = 1-0) survey in a portion of the third Galactic quadrant (TGQ): $l$ = [219.75, 229.75]$^\circ$ and $b$ = [-5.25, 5.25]$^\circ$. The high-resolution and high-sensitivity data sets help to unravel the distributions and physical properties of the molecular clouds (MCs) in the mapped area. In the LSR velocity range from -1 to 85 km/s, the molecular material successfully traces the Local, Perseus, and Outer arms. In the TGQ, the Outer arm appears to be more prominent than that in the second Galactic quadrant (SGQ), but the Perseus arm is not as conspicuous as that in the SGQ. A total of 1,502 $^{12}$CO, 570 $^{13}$CO, and 53 C$^{18}$O molecular structures are identified, spanning over $\sim2$ and $\sim6$ orders of magnitude in size and mass, respectively. Tight mass-radius correlations and virial parameter-mass anticorrelations are observable. Yet, it seems that no clear correlations between velocity dispersion and effective radius can be found over the full dynamic range. The vertical distribution of the MCs renders evident pictures of the Galactic warp and flare.

astro-ph.GA↗

arXiv2022

Calibrating the Cepheid Period--Wesenheit Relation in the Gaia Bands using Galactic Open Cluster Cepheids

Establishing the period--Wesenheit relation requires independent and accurate distance measurements of classical Cepheids (DCEPs). The precise distance provided by an associated open cluster independently calibrates the period--Wesenheit relation of DCEPs. 51 DCEPs associated with open clusters are compiled using the constraints of five-dimensional astrometric information. By directly using Gaia DR3 parallax, the period--Wesenheit relation in the Gaia $G$ band is calibrated as $W_G = (-3.06 \pm 0.11) \log P + (-2.96 \pm 0.10)$. Compared with the results derived by directly adopting the DCEP parallaxes or using distance moduli, the Wesenheit magnitudes based on the cluster-averaged parallaxes exhibit a tighter relation with the period. Besides, there is a systematic offset between the observed Wesenheit absolute magnitudes of distant OC-DCEPs and their fitted magnitudes. After considering the parallax zero-point correction, the systematic offset can be reduced, yielding a probably better PW relation of $W_G = (-2.94 \pm 0.12) \log P + (-2.93 \pm 0.11)$.

astro-ph.SR↗

arXiv2022

Local Spiral Structure Traced by Red Clump Stars

Using the cross-matched data of Gaia EDR3 and the 2MASS Point Source Catalog, a sample of RC stars with parallax accuracies better than 20% is identified and used to reveal the nearby spiral pattern traced by old stars. As shown in the overdensity distribution of RC stars, there is an arc-like feature extended from $l~\sim$ 90$^\circ$ to $\sim$ 243$^\circ$, which passed close to the Sun. This feature is probably an arm segment traced by old stars, indicating the Galaxy potential in the vicinity of the Sun. By comparing to the spiral arms depicted by young objects, we found that there are considerable offsets between the two different components of Galactic spiral arms. The spiral arm traced by RC stars tends to have a larger pitch angle, hence a more loose wound pattern.

astro-ph.GA↗