分类： 天文学 >> 天文学 提交时间： 2023-02-19
Ian D. Roberts
Maojin Lang
Daria Trotsenko
Ashley Bemis
Sara L. Ellison
Lihwai Lin
Hsi-An Pan
Alessandro Ignesti
Sarah Leslie
Reinout J. van Weeren
摘要： With MaNGA integral field spectroscopy, we present a resolved analysis of star formation for 29 jellyfish galaxies in nearby clusters, identified from radio continuum imaging taken by the Low Frequency Array. Simulations predict enhanced star formation on the "leading half" of galaxies undergoing ram pressure stripping, and in this work we report observational evidence for this elevated star formation. The dividing line (through the galaxy center) that maximizes this star formation enhancement is systematically tied to the observed direction of the ram pressure stripped tail, suggesting a physical connection between ram pressure and this star formation enhancement. We also present a case study on the distribution of molecular gas in one jellyfish galaxy from our sample, IC3949, using ALMA CO J=1-0, HCN J=1-0, and HCO$^+$ J=1-0 observations from the ALMaQUEST survey. The $\mathrm{H_2}$ depletion time (as traced by CO) in IC3949 ranges from $\sim\!1\,\mathrm{Gyr}$ in the outskirts of the molecular gas disk to $\sim\!11\,\mathrm{Gyr}$ near the galaxy center. IC3949 shows a clear region of enhanced star formation on the leading half of the galaxy where the average depletion time is $\sim\!2.7\,\mathrm{Gyr}$, in line with the median value for the galaxy on the whole. Dense gas tracers, HCN and HCO$^+$, are only detected at the galaxy center and on the leading half of IC3949. Our results favour a scenario in which ram pressure compresses the interstellar medium, promoting the formation of molecular gas that in turn fuels a localized increase of star formation.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
William M. Baker
Roberto Maiolino
Francesco Belfiore
Asa F. L. Bluck
Mirko Curti
Dominika Wylezalek
Caroline Bertemes
M. S. Bothwell
Lihwai Lin
Mallory Thorp
Hsi-An Pan
摘要： We investigate the relationship between the star formation rate (SFR), stellar mass ($M_*$) and molecular gas mass ($M_{H_2}$) for local star-forming galaxies. We further investigate these relationships for high-z (z=1-3) galaxies and for the hosts of a local sample of Active Galactic Nuclei (AGN). We explore which of these dependencies are intrinsic and which are an indirect by-product by employing partial correlation coefficients and random forest regression. We find that for local star-forming galaxies, high-z galaxies, and AGN host galaxies, the Schmidt-Kennicutt relation (SK, between $M_{H_2}$ and SFR), and the Molecular Gas Main Sequence (MGMS, between $M_{H_2}$ and $M_*$) are intrinsic primary relations, while the relationship between $M_*$ and SFR, i.e. the Star-Forming Main Sequence (SFMS), is an indirect by-product of the former two. Hence the Star-Forming Main Sequence is not a fundamental scaling relation for local or high-redshift galaxies. We find evidence for both the evolution of the MGMS and SK relation over cosmic time, where, at a given stellar mass, the higher the redshift, the greater the molecular gas mass and the star formation efficiency. We offer a parameterisation of both the MGMS and SK relation's evolution with redshift, showing how they combine to form the observed evolution of the SFMS. In addition, we find that the local AGN host galaxies follow an AGN-MGMS relation (as well as a AGN-SK relation), where the MGMS is offset to lower $M_{H_2}$ for a given $M_*$ compared to local SF galaxies.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Lihwai Lin
Sara L. Ellison
Hsi-An Pan
Mallory Thorp
Po-Chieh Yu
Francesco Belfiore
Bau-Ching Hsieh
Roberto Maiolino
S. Ramya
Sebastian Sanchez
Yung-Chau Su
摘要： We utilize the ALMA-MaNGA QUEnch and STar formation (ALMaQUEST) survey to investigate the kpc-scale scaling relations, presented as the resolved star forming main sequence (rSFMS: $\Sigma_{\rm SFR}$ vs. $\Sigma_{*}$), the resolved Schmidt-Kennicutt relation (rSK: $\Sigma_{\rm SFR}$ vs. $\Sigma_{\rm H_{2}}$), and the resolved molecular gas main sequence (rMGMS: $\Sigma_{\rm H_{2}}$ vs. $\Sigma_{*}$), for 11478 star-forming and 1414 retired spaxels (oversampled by a factor of $\sim20$) located in 22 green valley (GV) and 12 main sequence (MS) galaxies. For a given galaxy type (MS or GV), the retired spaxels are found to be offset from the sequences formed by the star-forming spaxels on the rSFMS, rSK, and rMGMS planes, toward lower absolute values of sSFR, SFE, and $f_{\rm H_{2}}$ by $\sim$ 1.1, 0.6, and 0.5 dex. The scaling relations for GV galaxies are found to be distinct from that of the MS galaxies, even if the analyses are restricted to the star-forming spaxels only. It is found that for star-forming spaxels, sSFR, SFE, and $f_{\rm H_{2}}$ in GV galaxies are reduced by $\sim$0.36, 0.14, and 0.21 dex, respectively, compared to those in MS galaxies. Therefore, the suppressed sSFR/SFE/$f_{\rm H_{2}}$ in GV galaxies are associated with not only an increased proportion of retired regions in GV galaxies but also a depletion of these quantities in star-forming regions. Finally, the reduction of SFE and $f_{\rm H_{2}}$ in GV galaxies relative to MS galaxies is seen in both bulge and disk regions (albeit with larger uncertainties), suggesting that statistically, quenching in the GV population may persist from the inner to the outer regions.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Hung-Yu Jian
Lihwai Lin
Bau-Ching Hsieh
Kai-Yang Lin
Keiichi Umetsu
Carlos Lopez-Coba
Yusei Koyama
Chin-Hao Hsu
Yung-Chau Su
Yu-Yen Chang
Tadayuki Kodama
Yutaka Komiyama
Surhud More
Atsushi J. Nishizawa
Masamune Oguri
Ichi Tanaka
摘要： We utilize the Hyper Suprime-Cam (HSC) Wide Survey to explore the properties of galaxies located in the voids identified from the Baryon Oscillation Spectroscopic Survey (BOSS) up to z~0.7. The HSC reaches i~25, allowing us to characterize the void galaxies down to 10$^{9.2}$ solar mass. We find that the revised void galaxy densities, when including faint galaxies in voids defined by bright galaxies, are still underdense compared to the mean density from the entire field. In addition, we classify galaxies into star-forming, quiescent, and green valley populations, and find that void galaxies tend to have slightly higher fractions of star-forming galaxies under the mass and redshift control, although the significance of this result is only moderate (2$\sigma$). However, when we focus on the star-forming population, the distribution of the specific star formation rate (sSFR) of void galaxies shows little difference from that of the control galaxies. Similarly, the median sSFR of star-forming void galaxies is also in good agreement with that of the star-forming control galaxies. Moreover, the effective green valley fraction of void galaxies, defined as the number of green valley galaxies over the number of nonquiescent galaxies, is comparable to that of the control ones, supporting the suggestion that void and control galaxies evolve under similar physical processes and quenching frequencies. Our results thus favor a scenario of the galaxy assembly bias.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
William M. Baker
Roberto Maiolino
Francesco Belfiore
Mirko Curti
Asa F. L. Bluck
Lihwai Lin
Sara L. Ellison
Mallory Thorp
Hsi-An Pan
摘要： We study the scaling relations between gas-phase metallicity, stellar mass surface density ($\Sigma _*$), star formation rate surface density ($\Sigma _{SFR}$), and molecular gas surface density ($\Sigma_{H_2}$) in local star-forming galaxies on scales of a kpc. We employ optical integral field spectroscopy from the MaNGA survey, and ALMA data for a subset of MaNGA galaxies. We use Partial Correlation Coefficients and Random Forest regression to determine the relative importance of local and global galactic properties in setting the gas-phase metallicity. We find that the local metallicity depends primarily on $\Sigma _*$ (the resolved mass-metallicity relation, rMZR), and has a secondary anti-correlation with $\Sigma _{SFR}$ (i.e. a spatially-resolved version of the 'Fundamental Metallicity Relation', rFMR). We find that $\Sigma_{H_2}$ is less important than $\Sigma_{SFR}$ in determining the local metallicity. This result indicates that gas accretion, resulting in local metallicity dilution and local boosting of star formation, is unlikely to be the primary origin of the rFMR. The local metallicity depends also on the global properties of galaxies. We find a strong dependence on the total stellar mass ($M_*$) and a weaker (inverse) dependence on the total SFR. The global metallicity scaling relations, therefore, do not simply stem out of their resolved counterparts; global properties and processes, such as the global gravitational potential well, galaxy-scale winds and global redistribution/mixing of metals, likely contribute to the local metallicity, in addition to local production and retention.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Gaoxiang Jin
Y. Sophia Dai
Hsi-An Pan
Lihwai Lin
Cheng Li
Bau-Ching Hsieh
Shiyin Shen
Fang-Ting Yuan
Shuai Feng
Cheng Cheng
Hai Xu
Jia-Sheng Huang
Kai Zhang
摘要： The role of active galactic nuclei (AGNs) during galaxy interactions and how they influence the star formation in the system are still under debate. We use a sample of 1156 galaxies in galaxy pairs or mergers (hereafter `pairs') from the MaNGA survey. This pair sample is selected by the velocity offset, projected separation, and morphology, and is further classified into four cases along the merger sequence based on morphological signatures. We then identify a total of 61 (5.5%) AGNs in pairs based on the emission-line diagnostics. No evolution of the AGN fraction is found, either along the merger sequence or compared to isolated galaxies (5.0%). We observe a higher fraction of passive galaxies in galaxy pairs, especially in the pre-merging cases, and associate the higher fraction to their environmental dependence. The isolated AGN and AGN in pairs show similar distributions in their global stellar mass, star formation rate (SFR), and central [OIII] surface brightness. AGNs in pairs show radial profiles of increasing specific SFR and declining Dn4000 from center to outskirts, and no significant difference from the isolated AGNs. This is clearly different from star-forming galaxies (SFGs) in our pair sample, which show enhanced central star formation, as reported before. AGNs in pairs have lower Balmer decrements at outer regions, possibly indicating less dust attenuation. Our findings suggest that AGNs likely follow an inside-out quenching and the merger impact on the star formation in AGNs is less prominent than in SFGs.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Xihan Ji
Cheng Li
Renbin Yan
Houjun Mo
Lihwai Lin
Hu Zou
Jianhui Lian
David V. Stark
Rogemar A. Riffel
Hsi-An Pan
Dmitry Bizyaev
Kevin Bundy
摘要： H$\alpha$ blobs are off-galaxy emission-line regions with weak or no optical counterparts. They are mostly visible in H$\alpha$ line, appearing as concentrated blobs. Such unusual objects have been rarely observed and studied, and their physical origin is still unclear. We have identified 13 H$\alpha$ blobs in the public data of MaNGA survey, by visually inspecting both the optical images and the spatially resolved maps of H$\alpha$ line for $\sim 4600$ galaxy systems. Among the 13 H$\alpha$ blobs, 2 were reported in previously MaNGA-based studies and 11 are newly discovered. This sample, though still small in size, is by far the largest sample with both deep imaging and integral field spectroscopy. Therefore, for the first time we are able to perform statistical studies to investigate the physical origin of H$\alpha$ blobs. We examine the physical properties of these H$\alpha$ blobs and their associated galaxies, including their morphology, environments, gas-phase metallicity, kinematics of ionized gas, and ionizing sources. We find that the H$\alpha$ blobs in our sample can be broadly divided into two groups. One is associated with interacting/merging galaxy systems, of which the ionization is dominated by shocks or diffuse ionized gas. It is likely that these H$\alpha$ blobs used to be part of their nearby galaxies, but were stripped away at some point due to tidal interactions. The other group is found in gas-rich systems, appearing as low-metallicity star-forming regions that are visually detached from the main galaxy. These H$\alpha$ blobs could be associated with faint disks, spiral arms, or dwarf galaxies.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We use machine learning techniques to classify galaxy merger stages, which can unveil physical processes that drive the star formation and active galactic nucleus (AGN) activities during galaxy interaction. The sample contains 4,690 galaxies from the integral field spectroscopy survey SDSS-IV MaNGA, and can be separated to 1,060 merging galaxies and 3630 non-merging or unclassified galaxies. For the merger sample, there are 468, 125, 293, and 174 galaxies in (1) incoming pair phase, (2) first pericentric passage phase, (3) aproaching or just passing the apocenter, and (4) final coalescence phase or post-mergers. With the information of projected separation, line-of-sight velocity difference, SDSS gri images, and MaNGA Ha velocity map, we are able to classify the mergers and their stages with good precision, which is the most important score to identify interacting galaxies. For the 2-phase classification (binary; non-merger and merger), the performance can be high (precision>0.90) with LGBMClassifier. We find that sample size can be increased by rotation, so the 5-phase classification (non-merger, 1, 2, 3, and 4 merger stages) can be also good (precision>0.85). The most important features come from SDSS gri images. The contribution from MaNGA Ha velocity map, projected separation, and line-of-sight velocity difference can further improve the performance by 0-20%. In other words, the image and the velocity information are sufficient to capture important features of galaxy interactions, and our results can apply to the entire MaNGA data as well as future all-sky surveys.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Wei-Hao Wang
Sebastien Foucaud
Bau-Ching Hsieh
Hung-Yu Jian
Lihwai Lin
Yen-Ting Lin
Jean Coupon
Yasuhiro Hashimoto
Masami Ouchi
Kazuhiro Shimasaku
Youichi Ohyama
Keiichi Umetsu
Shiang-Yu Wang
Tzu-Ching Chang
摘要： The Subaru Hyper Suprime-Cam (HSC) Strategic Survey is the latest-generation
multi-band optical imaging survey for galaxy evolution and structure formation.
The "Ultra-Deep" component of the HSC survey provides $grizy$ broad-band images
over $\sim3.4$ deg$^2$ to detection limits of $\sim26$-28 AB, along with
narrow-band images, in the COSMOS and the SXDS fields. These images provide an
unprecedented combination of depths and area coverage, for the studies galaxies
up to $z\sim7$. However, the lack of coverage at $<4000$ Ang implies incomplete
sampling of the rest-frame UV at $z\lesssim 3$, which is critically needed for
understanding the buildup of stellar mass in the later cosmic time. We
conducted a multi-year CFHT $u^\ast$-band imaging campaign in the two HSC
Ultra-Deep fields with CFHT MegaCam. By including shallower archival data, we
reach 5-$\sigma$ depths of $u^\ast=28.1$ and 28.4 (AB) at the centers of the
COSMOS and SXDS fields, respectively, and $u^\ast=27.7$ and 27.8 in the central
1 deg$^2$ fields. The image quality is $\gtrsim0.90$ arcsec, fairly good for
the $u^\ast$ band. Both the photometric and astrometric quality of our data are
excellent. We show that the combination of our $u^\ast$-band and HSC data can
lead to high-quality photometric redshifts at $z=0$-3, and robust measurements
of rest-frame UV on galaxies at $0.4
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Justin Atsushi Otter
Kate Rowlands
Katherine Alatalo
Ho-Hin Leung
Vivienne Wild
Yuanze Luo
Andreea O. Petric
Elizaveta Sazonova
David V. Stark
Timothy Heckman
Timothy A. Davis
Sara Ellison
K. Decker French
William Baker
Asa F. L. Bluck
Lauranne Lanz
Lihwai Lin
Charles Liu
Carlos López Cobá
Karen L. Masters
摘要： Post-starburst galaxies (PSBs) have recently and rapidly quenched their star-formation, thus they are an important way to understand how galaxies transition from star-forming late-types to quiescent early-types. The recent discovery of large cold gas reservoirs in PSBs calls into question the theory that galaxies must lose their gas to become quiescent. Optical Integral Field Spectroscopy (IFS) surveys have revealed two classes of PSBs: central PSBs with central quenching regions and ring PSBs with quenching in their outskirts. We analyze a sample of 13 nearby (z < 0.1) PSBs with spatially resolved optical IFS data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey and matched resolution Atacama Large (sub-)Millimeter Array (ALMA) observations of $^{12}$CO(1-0). Disturbed stellar kinematics in 7/13 of our PSBs and centrally concentrated molecular gas is consistent with a recent merger for most of our sample. In galaxies without merger evidence, alternate processes may funnel gas inwards and suppress star-formation, which may include outflows, stellar bars, and minor mergers or interactions. The star-formation efficiencies of the post-starburst regions in nearly half our galaxies are suppressed while the gas fractions are consistent with star-forming galaxies. AGN feedback may drive this stabilization, and we observe AGN-consistent emission in the centers of 5/13 galaxies. Finally, our central and ring PSBs have similar properties except the ionized and molecular gas in central PSBs is more disturbed. Overall, the molecular gas in our PSBs tends to be compact and highly disturbed, resulting in concentrated gas reservoirs unable to form stars efficiently.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Adam K. Leroy
Alberto D. Bolatto
Karin Sandstrom
Erik Rosolowsky
Ashley. T. Barnes
F. Bigiel
Médéric Boquien
Jakob S. den Brok
Yixian Cao
Jérémy Chastenet
Mélanie Chevance
I-Da Chiang
Ryan Chown
Dario Colombo
Sara L. Ellison
Eric Emsellem
Kathryn Grasha
Jonathan D. Henshaw
Annie Hughes
Ralf S. Klessen
摘要： We explore the relationship between mid-infrared (mid-IR) and CO rotational line emission from massive star-forming galaxies, which is one of the tightest scalings in the local universe. We assemble a large set of unresolved and moderately ($\sim 1$ kpc) spatially resolved measurements of CO (1-0) and CO (2-1) intensity, $I_{\rm CO}$, and mid-IR intensity, $I_{\rm MIR}$, at 8, 12, 22, and 24$\mu$m. The $I_{\rm CO}$ vs. $I_{\rm MIR}$ relationship is reasonably described by a power law with slopes $0.7{-}1.2$ and normalization $I_{\rm CO} \sim 1$ K km s$^{-1}$ at $I_{\rm MIR} \sim 1$ MJy sr$^{-1}$. Both the slopes and intercepts vary systematically with choice of line and band. The comparison between the relations measured for CO~(1-0) and CO (2-1) allow us to infer that $R_{21} \propto I_{\rm MIR}^{0.2}$, in good agreement with other work. The $8\mu$m and $12\mu$m bands, with strong PAH features, show steeper CO vs. mid-IR slopes than the $22\mu$m and $24\mu$m, consistent with PAH emission arising not just from CO-bright gas but also from atomic or CO-dark gas. The CO-to-mid-IR ratio correlates with global galaxy stellar mass ($M_\star$) and anti-correlates with SFR/$M_\star$. At $\sim 1$ kpc resolution, the first four PHANGS-JWST targets show CO to mid-IR relationships that are quantitatively similar to our larger literature sample, including showing the steep CO-to-mid-IR slopes for the JWST PAH-tracing bands, although we caution that these initial data have a small sample size and span a limited range of intensities.
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