星形成率密度（SFRD）是星系演化中的重要工具，使我们能够识别星系在哪个宇宙时期更高效地形成恒星。对于低质量星形成星系，SFRD作为恒星质量的函数可以直接与星系恒星质量函数（GSMF）相关联。由于观测矮星系的挑战导致GSMF在低质量端存在不确定性，因此推导基于质量的SFRD对理解星系形成至关重要。在宇宙学体积内，SFRD的测量比数密度更完整，因为具有更高SFR的星系更容易被探测和表征。本研究使用两个不同样本推导SFRD：一个基于MUSE WIDE和MUSE Hubble Ultra Deep Field IFU光谱巡天，另一个基于GAMA光谱巡天。第一个样本包含27个z < 0.2的Hα选源星形成星系，第二个样本包含7579个z < 0.06的r波段选源星系。第一个样本的恒星形成率由Hα发射线通量测量推导，第二个样本使用MagPhys SED拟合推导。结果显示SFRD在最低恒星质量10^5.5 M⊙处的行为与恒定斜率（在log SFRD对log恒星质量图中）一致，因此GSMF中不存在翻转。结果还表明MUSE WIDE和HUDF样本所考虑的体积处于低密度状态。
英文摘要：
The star formation rate density (SFRD) is an important tool in galaxy evolution that allows us to identify at which cosmic time galaxies are more efficient at forming stars. For low-mass star-forming galaxies, the SFRD as a function of stellar mass can be straightforwardly related to the galaxy stellar mass function (GSMF). Given the uncertainty of the GSMF at the low-mass end, due to the challenges in observing dwarf galaxies, deriving the SFRD with respect to mass may be crucial to understand galaxy formation. Measurement of SFRD is more complete than number density in a cosmological volume because galaxies with higher SFR are easier to detect and characterize. In this work, the SFRD is derived using two different samples, one using the MUSE WIDE and MUSE Hubble Ultra Deep Field IFU spectroscopic surveys, and another using the GAMA spectroscopic survey. The first sample comprised a total of 27 star-forming galaxies at z $<$ 0.2 (H$α$ selected), whereas the second contained 7579 galaxies at z $<$ 0.06 ($r$-band selected). The star formation rates are derived from measurements of the H$α$ emission line fluxes for the first sample, and using MagPhys SED fitting for the second one. The results show the behaviour of the SFRD to the lowest stellar masses of 10$^{5.5}$ $M_{\odot}$, consistent with a constant slope (in log SFRD versus log stellar mass) and thus no turn-over in the GSMF. The results also suggest that the volume considered for the MUSE WIDE and HUDF sample is underdense.
The Galaxy And Mass Assembly Survey (GAMA) covers five fields with highly complete spectroscopic coverage ($>95$ per cent) to intermediate depths ($r<19.8$ or $i < 19.0$ mag), and collectively spans 250 square degrees of Equatorial or Southern sky. Four of the GAMA fields (G09, G12, G15 and G23) reside in the ESO VST KiDS and ESO VISTA VIKING survey footprints, which combined with our GALEX, WISE and Herschel data provide deep uniform imaging in the $FUV\,NUV\,ugriZYJHK_s\,W1\,W2\,W3\,W4\,P100\,P160\,S250\,S350\,S500$ bands. Following the release of KiDS DR4, we describe the process by which w…
In this study we present a new experimental design using clustering-based redshift inference to measure the evolving galaxy luminosity function (GLF) spanning 5.5 decades from $L \sim 10^{11.5}$ to $ 10^6 ~ \mathrm{L}_\odot$. We use data from the Galaxy And Mass Assembly (GAMA) survey and the Kilo-Degree Survey (KiDS). We derive redshift distributions in bins of apparent magnitude to the limits of the GAMA-KiDS photometric catalogue: $m_r \lesssim 23$; more than a decade in luminosity beyond the limits of the GAMA spectroscopic redshift sample via clustering-based redshift inference. This tech…
We aim to investigate the galaxy environment in GAMA Galaxy Groups Catalogue (G3C) using a volume-limited galaxy sample from the Kilo Degree Survey Data Release 3. The k-Nearest Neighbour technique is adapted to take into account the probability density functions (PDFs) of photometric redshifts in our calculations. This algorithm was tested on simulated KiDS tiles, showing its capability of recovering the relation between galaxy colour, luminosity and local environment. The characterization of the galaxy environment in G3C groups shows systematically steeper density contrasts for more massive …
Using a volume-limited sample of 550 groups from the Galaxy And Mass Assembly (GAMA) Galaxy Group Catalogue spanning the halo mass range $12.8 < \log [M_{h}/M] < 14.2$, we investigate the merging potential of central Brightest Group Galaxies (BGGs). We use spectroscopically-confirmed close-companion galaxies as an indication of the potential stellar mass build-up of low-redshift BGGs, $z \leq 0.2$. We identify 17 close-companion galaxies with projected separations $r_{p} < 30$ kpc, relative velocities $Δv \leq 300$ km s$^{-1}$, and stellar-mass ratios $M_{BGG}/M_{CC} \leq 4$ relative to the BG…
The star formation rate in galaxies is well known to correlate with stellar mass (the `star-forming main sequence'). Here we extend this further to explore any additional dependence on galaxy surface brightness, a proxy for stellar mass surface density. We use a large sample of low redshift ($z \leq 0.08$) galaxies from the GAMA survey which have both SED derived star formation rates and photometric bulge-disc decompositions, the latter providing measures of disc surface brightness and disc masses. Using two samples, one of galaxies fitted by a single component with Sérsic index below 2 and on…
We explore how the group environment may affect the evolution of star-forming galaxies. We select 1197 Galaxy And Mass Assembly (GAMA) groups at $0.05\leq z \leq 0.2$ and analyze the projected phase space (PPS) diagram, i.e. the galaxy velocity as a function of projected group-centric radius, as a local environmental metric in the low-mass halo regime $10^{12}\leq (M_{200}/M_{\odot})< 10^{14}$. We study the properties of star-forming group galaxies, exploring the correlation of star formation rate (SFR) with radial distance and stellar mass. We find that the fraction of star-forming group memb…
Galaxy And Mass Assembly (GAMA): The Most Isolated GAMA Galaxies
University of Bristol（布里斯托大学）；Finnish Centre for Astronomy with ESO, University of Turku（芬兰埃索天文学中心，图尔库大学）；Department of Physics and Astronomy, Botswana International University of Science and Technology（博茨瓦纳国际科学与技术大学物理与天文系）；Astrophysics Research Institute, Liverpool John Moores University（利物浦约翰摩尔斯大学天体物理研究所）；Macquarie University（麦考瑞大学）
We study the radio emission of the most massive galaxies in a sample of dynamically relaxed and un-relaxed galaxy groups from Galaxy and Mass Assembly (GAMA). The dynamical state of the group is defined by the stellar dominance of the brightest group galaxy, e.g. the luminosity gap between the two most luminous members, and the offset between the position of the brightest group galaxy and the luminosity centroid of the group. We find that the radio luminosity of the most massive galaxy in the group strongly depends on its environment, such that the brightest group galaxies in dynamically young…
Galaxy And Mass Assembly (GAMA): Trends in galaxy colours, morphology, and stellar populations with large scale structure, group, and pair environments
We study the star formation rate (SFR), stellar mass ($M_{\star}$) and the gas metallicity (Z) for 4,636 galaxy pairs using the Galaxy And Mass Assembly (GAMA) survey. Our galaxy pairs lie in a redshift range of 0 $<$ $z$ $<$ 0.35, mass range of 7.5 $<$ log( M$_{\star}$/ M$_\odot$) $<$ 11.5 and $ΔV$ $<$ 1000 km s$^{-1}$. We explore variations in SFR and Z from three point of views: multiplicity, pair separation and dynamics. We define multiplicity as the number of galaxies paired with a single galaxy, and analyzed for the first time variations in SFR and Z for both, single pairs and pairs with…
Galaxy And Mass Assembly (GAMA): Deconstructing the galaxy stellar mass function by star formation and environment
Hamburger Sternwarte, Universität Hamburg（汉堡天文台，汉堡大学）；Cluster of Excellence Quantum Universe, Universität Hamburg（量子宇宙卓越集群，汉堡大学）；International Centre for Radio Astronomy Research (ICRAR), University of Western Australia（国际无线电天文学研究中心，西澳大利亚大学）；Centre for Astrophysics and Supercomputing, Swinburne University of Technology（天体物理学与超级计算中心，斯威本科技大学）
Understanding the connection between nuclear activity and galaxy environment remains critical in constraining models of galaxy evolution. By exploiting extensive catalogued data from the Galaxy and Mass Assembly (GAMA) survey, we identify a representative sample of 205 quasars at 0.1 < z < 0.35 and establish a comparison sample of galaxies, closely matched to the quasar sample in terms of both stellar mass and redshift. On scales <1 Mpc, the galaxy number counts and group membership of quasars appear entirely consistent with those of the matched galaxy sample. Despite this, we find that quasar…
Aims. We aim to investigate if the environment (characterised by the host dark matter halo mass) plays any role in shaping the galaxy star formation main sequence (MS). Methods. The Galaxy and Mass Assembly project (GAMA) combines a spectroscopic survey with photometric information in 21 bands from the far-ultraviolet (FUV) to the far-infrared (FIR). Stellar masses and dust-corrected star-formation rates (SFR) are derived from spectral energy distribution (SED) modelling using MAGPHYS. We use the GAMA galaxy group catalogue to examine the variation of the fraction of star-forming galaxies (SFG…
We present an entirely new sample of 388 low-mass galaxies ($M_\star \leq 10^{10} M_\odot$) that have spectroscopic signatures indicating the presence of massive black holes (BHs) in the form of active galactic nuclei (AGNs) or tidal disruption events (TDEs). Of these, 70 have stellar masses in the dwarf galaxy regime with $10^8 \lesssim M_\star/M_\odot \lesssim 10^{9.5}$. We identify the active galaxies by analyzing optical spectra of a parent sample of $\sim$23,000 low-mass emission-line galaxies in the Galaxy and Mass Assembly (GAMA) Survey Data Release 4, and employing four different diagn…
We use data from the GAMA and GALEX surveys to demonstrate that the UV upturn, an unexpected excess of ultraviolet flux from a hot stellar component, seen in the spectra of many early-type galaxies, arises from processes internal to individual galaxies with no measurable influence from the galaxies' larger environment. We first define a clean sample of passive galaxies without a significant contribution to their UV flux from low-level star formation. We confirm that galaxies with the optical colours of red sequence galaxies often have signs of residual star formation, which, without other info…
Strong gravitational lenses are a rare and instructive type of astronomical object. Identification has long relied on serendipity, but different strategies -- such as mixed spectroscopy of multiple galaxies along the line of sight, machine learning algorithms, and citizen science -- have been employed to identify these objects as new imaging surveys become available. We report on the comparison between spectroscopic, machine learning, and citizen science identification of galaxy-galaxy lens candidates from independently constructed lens catalogs in the common survey area of the equatorial fiel…
A fundamental bimodality of galaxies in the local Universe is apparent in many of the features used to describe them. Multiple sub-populations exist within this framework, each representing galaxies following distinct evolutionary pathways. Accurately identifying and characterising these sub-populations requires that a large number of galaxy features be analysed simultaneously. Future galaxy surveys such as LSST and Euclid will yield data volumes for which traditional approaches to galaxy classification will become unfeasible. To address this, we apply a robust $k$-means unsupervised clusterin…
We present a study of the relationships and environmental dependencies between stellar mass, star formation rate, and gas metallicity for more than 700 galaxies in groups up to redshift 0.35 from the Galaxy And Mass Assembly (GAMA) survey. To identify the main drivers, our sample was analyzed as a function of group-centric distance, projected galaxy number density, and stellar mass. By using control samples of more than 16000 star-forming field galaxies and volume limited samples, we find that the highest enhancement in SFR (0.3 dex) occurs in galaxies with the lowest local density. In contras…
Galaxy populations show bimodality in a variety of properties: stellar mass, colour, specific star-formation rate, size, and Sérsic index. These parameters are our feature space. We use an existing sample of 7556 galaxies from the Galaxy and Mass Assembly (GAMA) survey, represented using five features and the K-means clustering technique, showed that the bimodalities are the manifestation of a more complex population structure, represented by between 2 and 6 clusters. Here we use Self Organizing Maps (SOM), an unsupervised learning technique which can be used to visualize similarity in a highe…
We present improved modelling of the redshift-space distortions of galaxy clustering that arise from peculiar velocities. We create mock galaxy catalogues in the framework of the halo model, using data from the Bolshoi project. These mock galaxy populations are inserted into the haloes with additional degrees of freedom that govern spatial and kinematical biases of the galaxy populations relative to the dark matter. We explore this generalised halo model with an MCMC algorithm, comparing the predictions to data from the Galaxy And Mass Assembly (GAMA) survey, and thus derive one of the first c…
We use multi-wavelength data from the Galaxy and Mass Assembly (GAMA) survey to explore the cause of red optical colours in nearby (0.002<z<0.06) spiral galaxies. We show that the colours of red spiral galaxies are a direct consequence of some environment-related mechanism(s) which has removed dust and gas, leading to a lower star formation rate. We conclude that this process acts on long timescales (several Gyr) due to a lack of morphological transformation associated with the transition in optical colour. The sSFR and dust-to-stellar mass ratio of red spiral galaxies is found to be statistic…
Galaxy And Mass Assembly (GAMA): The Bright Void Galaxy Population in the Optical and Mid-IR
我们研究星系的性质在星系和质量大会（GAMA）调查位于半径为$>10~h^{-1}$ Mpc的空隙。利用GAMA赤道巡天，592个空星系被识别出比$M_{r} = -18.4$（我们的星等完整性极限）亮z~0.1。利用$W_{\rm{Hα}}$与[NII]/H $α$（WHAN）谱线强度诊断图，我们将它们的谱线划分为恒星形成、活动星系核或由古老的恒星星族支配。对于质量大于$5\times10^{9}$ M $_{\odot}$的天体，我们在WHAN诊断图中识别出了26个具有老恒星星族的空星系样本，这些星系被归类为被动星系和退休星系，否则它们的光谱中没有任何发射线。当与WISE中红外测光匹配时，这些被动和退休的星系显示出一系列的中红外颜色，其中一些空洞星系显示出[4.6]-[12]与完全猝灭的恒星星族不一致的颜色，随机抽取的非空洞比较样本也显示出类似的颜色分布。我们假设，这些星系的主机模糊的恒星形成，否则他们是恒星形成的中心区域以外的单纤维光谱的目标。当匹配到随机抽取的非空星系样本时，空星系和非空星系在光学和中红外颜色、形态和恒星形成活动方面表现出相似的性质，这表明它们具有可比的质量组装和淬灭历史。在中红外[4.6]-[12]色中可以看到一种趋势，这样淬灭色/被动色<1.5的空星系和非空星系的质量通常都高于$10^{10}$ M $_{\odot}$，其中内部驱动过程在星系演化中扮演…
We apply the spectral energy distribution (SED) fitting code ProSpect to multiwavelength imaging for $\sim$7,000 galaxies from the GAMA survey at $z<0.06$, in order to extract their star formation histories. We combine a parametric description of the star formation history with a closed-box evolution of metallicity where the present-day gas-phase metallicity of the galaxy is a free parameter. We show with this approach that we are able to recover the observationally determined cosmic star formation history (CSFH), an indication that stars are being formed in the correct epoch of the Universe, …
We explore the clustering of galaxy groups in the Galaxy and Mass Assembly (GAMA) survey to investigate the dependence of group bias and profile on separation scale and group mass. Due to the inherent uncertainty in estimating the group selection function, and hence the group auto-correlation function, we instead measure the projected galaxy--group cross-correlation function. We find that the group profile has a strong dependence on scale and group mass on scales $r_\bot \lesssim 1 h^{-1} \mathrm{Mpc}$. We also find evidence that the most massive groups live in extended, overdense, structures.…
In galaxy clusters, efficiently accreting active galactic nuclei (AGN) are preferentially located in the infall regions of the cluster projected phase-space, and are rarely found in the cluster core. This has been attributed to both an increase in triggering opportunities for infalling galaxies, and a reduction of those mechanisms in the hot, virialised, cluster core. Exploiting the depth and completeness ($98\,$per cent at $r<19.8\,$mag) of the Galaxy And Mass Assembly survey (GAMA), we probe down the group halo mass function to assess whether AGN are found in the same regions in groups as th…
In this paper we test if nearby blue spheroid (BSphs) galaxies may become the progenitors of star-forming spiral galaxies or passively-evolving elliptical galaxies. Our sample comprises 428 galaxies of various morphologies in the redshift range 0.002<z<0.02 (8-87 Mpc) with panchromatic data from the Galaxy and Mass Assembly survey. We find that BSph galaxies are structurally (mean effective surface brightness, effective radius) very similar to their passively-evolving red counterparts. However, their star-formation and other properties such as colour, age and metallicity are more like star-for…
We use KiDS weak lensing data to measure variations in mean halo mass as a function of several key galaxy properties (namely: stellar colour, specific star formation rate, Sersic index, and effective radius) for a volume-limited sample of GAMA galaxies in a narrow stellar mass range ($M_* \sim 2$--$5 \times 10^{10}$ Msol). This mass range is particularly interesting, inasmuch as it is where bimodalities in galaxy properties are most pronounced, and near to the break in both the galaxy stellar mass function and the stellar-to-halo mass relation (SHMR). In this narrow mass range, we find that bo…
Using a combined and consistently analysed GAMA, G10-COSMOS, and 3D-HST dataset we explore the evolution of the galaxy stellar-mass function over lookback times $t_{\rm L} \in \left[0.2,12.5\right] {\rm h^{-1}_{70} Gyr}$. We use a series of volume limited samples to fit Schechter functions in bins of $\sim\!$constant lookback time and explore the evolution of the best-fit parameters in both single and two-component cases. In all cases, we employ a fitting procedure that is robust to the effects of Eddington bias and sample variance. Surprisingly, when fitting a two-component Schechter function…
How do galaxy properties (such as stellar mass, luminosity, star formation rate, and morphology) and their evolution depend on the mass of their host dark matter halo? Using the Galaxy and Mass Assembly (GAMA) group catalogue, we address this question by exploring the dependence on host halo mass of the luminosity function (LF) and stellar mass function (SMF) for grouped galaxies subdivided by colour, morphology and central/satellite. We find that spheroidal galaxies in particular dominate the bright and massive ends of the LF and SMF, respectively. More massive haloes host more massive and mo…
We analyse the metallicity histories of ~4,500 galaxies from the GAMA survey at z<0.06 modelled by the SED-fitting code ProSpect using an evolving metallicity implementation. These metallicity histories, in combination with the associated star formation histories, allow us to analyse the inferred gas-phase mass--metallicity relation. Furthermore, we extract the mass--metallicity relation at a sequence of epochs in cosmic history, to track the evolving mass--metallicity relation with time. Through comparison with observations of gas-phase metallicity over a large range of redshifts, we show tha…
We present surface photometry and stellar kinematics of NGC 4264, a lenticular galaxy in the region of the Virgo Cluster undergoing a tidal interaction with its neighbour, NGC 4261. We measured the bar radius and strength from SDSS imaging and the bar pattern speed from MUSE integral-field spectroscopy. We find that NGC 4264 hosts a strong and large bar, which is rotating fast. The accurate measurement of the bar rotation rate allows us to exclude that the formation of the bar was triggered by the ongoing interaction.
Intrinsic galaxy alignments are a source of bias for weak lensing measurements as well as a tool for understanding galaxy formation and evolution. In this work, we measure the alignment of shapes of satellite galaxies, in galaxy groups, with respect to the brightest group galaxy (BGG), as well as alignments of the BGG shape with the satellite positions, using the highly complete Galaxy And Mass Assembly (GAMA) spectroscopic survey and deep imaging from the Kilo Degree Survey. We control systematic errors with dedicated image simulations and measure accurate shapes using the DEIMOS shape measur…
