分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： To explore the effect of environment on star-formation and morphological transformation of high-redshift galaxies, we present a robust estimation of localized galaxy overdensity using a density estimator within the Bayesian probability framework.The maps of environmental overdensity at $0.5 10^{10.8} M_{\odot}$), the effect of environmental quenching is still significant up to $z \sim 2.5$. No significant environmental dependence is found in the distributions of S\'{e}rsic index and effective radius for SFGs and QGs separately. The primary role of environment might be to control the quiescent fraction. And the morphological parameters are primarily connected with star formation status. The similarity in the trends of quiescent fraction and S\'{e}rsic index along with stellar mass indicates that morphological transformation is accompanied with star formation quenching.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： To investigate the effects of environment in the quenching phase, we study
the empirical relations for green valley (GV) galaxies between overdensity and
other physical properties (i.e., effective radius $r_{\rm e}$, S\'{e}rsic
indices $n$, and specific star formation rate sSFR). Based on five 3D-{\it
HST}/CANDELS fields, we construct a large sample of 2126 massive ($M_{\star} >
10^{10} M_{\sun}$) GV galaxies at $0.5
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Several mechanisms for the transformation of blue star-forming to red quiescent galaxies have been proposed, and the green valley (GV) galaxies amid them are widely accepted in a transitional phase. Thus, comparing the morphological and environmental differences of the GV galaxies with early-type disks (ETDs; bulge dominated and having a disk) and late-type disks (LTDs; disk dominated) is suitable for distinguishing the corresponding quenching mechanisms. A large population of massive ($M_* \geqslant 10^{10}M_\odot$) GV galaxies at $0.5 \leqslant z \leqslant 1.5$ in 3D-HST/CANDELS is selected using extinction-corrected $(U-V)_{\rm rest}$ color. After eliminating any possible active galactic nucleus candidates and considering the "mass-matching", we finally construct two comparable samples of GV galaxies with either 319 ETD or 319 LTD galaxies. Compared to the LTD galaxies, it is found that the ETD galaxies possess higher concentration index and lower specific star formation rate, whereas the environments surrounding them are not different. This may suggest that the morphological quenching may dominate the star formation activity of massive GV galaxies rather than the environmental quenching. To quantify the correlation between the galaxy morphology and the star formation activity, we define a dimensionless morphology quenching efficiency $Q_{\rm mor}$ and find that $Q_{\rm mor}$ is not sensitive to the stellar mass and redshift. When the difference between the average star formation rate of ETD and LTD galaxies is about 0.7 $M_\odot \rm \;yr^{-1}$, the probability of $Q_{\rm mor}\gtrsim 0.2$ is higher than 90\%, which implies that the degree of morphological quenching in GV galaxies might be described by $Q_{\rm mor}\gtrsim 0.2$.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： To investigate star-forming activities in early-type galaxies, we select a sample of 52 star-forming S0 galaxies (SFS0s) from the SDSS-IV MaNGA survey. We find that SFS0s have smaller stellar mass compared to normal S0s in MaNGA. After matching the stellar mass to select the control sample, we find that the mean S\'{e}rsic index of SFS0s' bulges (1.76$\pm$0.21) is significantly smaller than that of the control sample (2.57$\pm$0.20), suggesting the existence of a pseudo bulge in SFS0s. After introducing the environmental information, SFS0s show smaller spin parameters in the field than in groups, while the control sample has no obvious difference in different environments, which may suggest different dynamical processes in SFS0s. Furthermore, with derived N/O and O/H abundance ratios, SFS0s in the field show nitrogen enrichment, providing evidence for the accretion of metal-poor gas in the field environment. To study the star formation relation, we show that the slope of the spatially resolved star formation main sequence is nearly 1.0 with MaNGA IFU data, confirming the self-regulation of star formation activities at the kpc scales.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： To figure out the effect of stellar mass and local environment on
morphological transformation and star formation quenching in galaxies, we use
the massive ($M_* \geq 10^{10} M_{\odot}$) galaxies at $0.5 \leq z \leq 2.5$ in
five fields of 3D-HST/CANDELS. Based on the {\it UVJ} diagnosis and the
possibility of possessing spheroid, our sample of massive galaxies are
classified into four populations: quiescent early-type galaxies (qEs),
quiescent late-type galaxies (qLs), star-forming early-type galaxies (sEs), and
star-forming late-type galaxies (sLs). It is found that the quiescent fraction
is significantly elevated at the high ends of mass and local environmental
overdensity, which suggests a clear dependence of quenching on both mass and
local environment. Over cosmic time, the mass dependence of galaxy quiescence
decreases while the local environment dependence increases. The early-type
fraction is found to be larger only at high-mass end, indicating a evident mass
dependence of morphological transformation. This mass dependence becomes more
significant at lower redshifts. Among the four populations, the fraction of
active galactic nucleus (AGN) in the qLs peaks at $2
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Shiying Lu
Qiusheng Gu
Xue Ge
Luis C. Ho
Yulong Gao
Zhengyi Chen
Ke Xu
Zhi-Yu Zhang
Yong Shi
Qirong Yuan
Min Bao
摘要： Comparing to the inactive and gas-poor normal lenticular galaxies (S0s) in the local universe, we study a barred star-forming S0 galaxy, PGC 34107, which has been observed by the Centro Astron\'{o}mico Hispano Alem\'{a}n (CAHA) 3.5-m telescope and the Northern Extended Millimeter Array (NOEMA). The spatially resolved ionized gas and molecular gas traced by $^{12}$CO(1-0), hereafter CO(1-0), show the similar distribution and kinematics to the stellar component with an off-center star-forming region, $\sim$380 pc away from the center. The resolved kinematics of molecular CO(1-0) emission reveals that there is a blueshifted (redshifted) velocity component on the receding (approaching) side of the galaxy along the stellar bar. This might provide a plausible evidence of non-circular motion, such as the bar-induced molecular gas inflow. The velocity of molecular gas inflow decreases with approaching towards the peak of the off-center star formation in the north, which might be associated with the inner Lindblad resonance (ILR). In addition to CO(1-0), we also detect the isotopic line of $^{13}$CO(1-0). Most $\rm H\alpha$, CO(1-0) and $^{13}$CO(1-0) emissions are concentrated on this northern star-forming region. We find that PGC 34107 follows the local stellar mass-metallicity relation, star-forming main sequence, and the Kennicutt-Schmidt law. The resolved and integrated molecular gas main sequence suggest that there is a higher gas fraction in the galaxy central region, which supports a scenario that the bar-induced gas reservoir provides the raw material, and subsequently triggers the central star formation.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Yulong Gao
Qiusheng Gu
Yong Shi
Luwenjia Zhou
Min Bao
Xiaoling Yu
Zhiyu Zhang
Tao Wang
Suzanne C. Madden
Matthew Hayes
Shiying Lu
Ke Xu
摘要： The physical mechanisms for starburst or quenching in less massive ($M_* < 10^{10} M_{\odot}$) galaxies are unclear. The merger is one of the inescapable processes referred to as both starburst and quenching in massive galaxies. However, the effects of the merger on star formation in dwarf galaxies and their evolution results are still uncertain. We aim to explore how to trigger and quench star formation in dwarf galaxies by studying the metal-poor gas-rich dwarf mergers based on the multi-band observations at a spatial resolution of $\sim$ 460 pc. We use the archival data of ALMA (band 3, 8) and VLT/MUSE to map CO($J=$1-0), [CI]($^3$P$_1 - ^3$P$_0$), and H$\alpha$ emission in one of the most extreme starburst merging dwarf galaxies, Haro 11. We find the molecular gas is assembled around the central two star-forming regions. The molecular/ionized gas and stellar components show complex kinematics, indicating that the gas is probably at a combined stage of collision of clouds and feedback from star formation. The peak location and distribution of [CI](1-0) strongly resemble the CO(1-0) emission, meaning that it might trace the same molecular gas as CO in such a dwarf merger starburst galaxy. The enhancement of line ratios ($\sim 0.5$) of [CI]/CO around knot C is probably generated by the dissociation of CO molecules by cosmic rays and far-ultraviolet photons. Globally, Haro 11 and its star-forming regions share similar SFEs as the high-$z$ starburst galaxies or the clumps in nearby (U)LIRGs. Given the high SFE, sSFR, small stellar mass, low metallicity, and deficient HI gas, Haro 11 could be an analog of high-$z$ dwarf starburst and the potential progenitor of the nearby less massive elliptical galaxies. The significantly smaller turbulent pressure and viral parameter will probably trigger the intense starbursts. We also predict that it will quench at $M_* < 8.5 \times 10^9 M_{\odot}$.
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