Ferrarese & Merritt (2000), Gebhardt et al. (2000), Magorrian et al. (1998) have shown that supermassive blackholes are related to the host galaxy. Then, Martini et al. (2003) and Simoes Lopes et al. (2007) have found that all active galactic nuclei have a dust structure (r ~ 100 pc) near the core and Tran et al. (2001) reported that the dust structure in the elliptical galaxy is more related to filamentary structure than other structure in active galactic nuclei(AGN). So, we started to find the correlation between active galactic nuclei (AGN) and circumnuclear dust. And According to the dust morphology classification by Tran et al., we classified circumnuclear dust of spiral galaxies.
[ Ferrarese & Merritt 2000. ApJ, 539, 9. ]
The masses of supermassive black holes correlate almost perfectly with the velocity dispersions of their host bulges, Mbh~σα, where α=4.8+/-0.5. The relation is much tighter than the relation between Mbh and bulge luminosity, with a scatter no larger than expected on the basis of measurement error alone. Black hole masses recently estimated by Magorrian et al. lie systematically above the Mbh-σ relation defined by more accurate mass estimates, some by as much as 2 orders of magnitude. The tightness of the Mbh-σ relation implies a strong link between black hole formation and the properties of the stellar bulge.
[ Gebhardt et al. 2000. ApJ, 539, 13. ]
We describe a correlation between the mass Mbh of a galaxy's central black hole and the luminosity-weighted line-of-sight velocity dispersion σe within the half-light radius. The result is based on a sample of 26 galaxies, including 13 galaxies with new determinations of black hole masses from Hubble Space Telescope measurements of stellar kinematics. The best-fit correlation is Mbh=1.2(+/-0.2)×108 Msolar(σe/200 km s-1)3.75 (+/-0.3) over almost 3 orders of magnitude in Mbh; the scatter in Mbh at fixed σe is only 0.30 dex, and most of this is due to observational errors. The Mbh-σe relation is of interest not only for its strong predictive power but also because it implies that central black hole mass is constrained by and closely related to properties of the host galaxy's bulge.
[ Magorrian et al. 1998. AJ, 115, 2285. ]
We construct dynamical models for a sample of 36 nearby galaxies with Hubble Space Telescope (HST) photometry and ground-based kinematics. The models assume that each galaxy is axisymmetric, with a two-integral distribution function, arbitrary inclination angle, a position-independent stellar mass-to-light ratio Upsilon, and a central massive dark object (MDO) of arbitrary mass M_•. They provide acceptable fits to 32 of the galaxies for some value of M_• and Upsilon the four galaxies that cannot be fitted have kinematically decoupled cores. The mass-to-light ratios inferred for the 32 well-fitted galaxies are consistent with the fundamental-plane correlation Upsilon ~ L^0.2, where L is galaxy luminosity. In all but six galaxies the models require at the 95% confidence level an MDO of mass M_• ~ 0.006M_bulge = 0.006UpsilonL. Five of the six galaxies consistent with M_• = 0 are also consistent with this correlation. The other (NGC 7332) has a much stronger upper limit on M_•. We predict the second-moment profiles that should be observed at HST resolution for the 32 galaxies that our models describe well. We consider various parameterizations for the probability distribution describing the correlation of the masses of these MDOs with other galaxy properties. One of the best models can be summarized thus: a fraction f ~= 0.97 of early-type galaxies have MDOs, whose masses are well described by a Gaussian distribution in log (M_•/M_bulge) of mean -2.28 and standard deviation ~0.51. There is also marginal evidence that M_• is distributed differently for ``core'' and ``power law'' galaxies, with core galaxies having a somewhat steeper dependence on M_bulge.
[ Martini et al. 2003. ApJ, 589, 774. ]
We present a detailed study of the relation between circumnuclear dust morphology, host-galaxy properties, and nuclear activity in nearby galaxies. We use our sample of 123 nearby galaxies with visible-near-infrared color maps from the Hubble Space Telescope to create well-matched, ``paired'' samples of 28 active and 28 inactive galaxies, as well as 19 barred and 19 unbarred galaxies, that have the same host-galaxy properties. Comparison of the barred and unbarred galaxies shows that grand-design nuclear dust spirals are found only in galaxies with a large-scale bar. These nuclear dust spirals, which are present in approximately one-third of all barred galaxies, also appear to be connected to the dust lanes along the leading edges of the large-scale bars. Grand-design nuclear spirals are more common than inner rings, which are present in only a small minority of the barred galaxies. Tightly wound nuclear dust spirals, in contrast, show a strong tendency to avoid galaxies with large-scale bars. Comparison of the active galactic nuclei (AGNs)and inactive samples shows that nuclear dust spirals, which may trace shocks and angular momentum dissipation in the interstellar medium, occur with comparable frequency in both active and inactive galaxies. The only difference between the active and inactive galaxies is that several inactive galaxies appear to completely lack dust structure in their circumnuclear region, while none of the AGNs lack this structure. The comparable frequency of nuclear spirals in active and inactive galaxies, combined with previous work that finds no significant difference in the frequency of bars or interactions between well-matched active and inactive galaxies, suggests that no universal fueling mechanism for low-luminosity AGNs operates at spatial scales greater than a ~100 pc radius from the galactic nuclei. The similarities of the circumnuclear environments of active and inactive galaxies suggest that the lifetime of nuclear activity is less than the characteristic inflow time from these spatial scales. An order-of-magnitude estimate of this inflow time is the dynamical timescale. This sets an upper limit of several million years to the lifetime of an individual episode of nuclear activity.
[ Simões Lopes et al. 2007. ApJ, 655, 718. ]
We present a detailed investigation of the incidence of circumnuclear dust structure in a large, well-matched sample of early-type galaxies with and without active galactic nuclei (AGNs). All 34 early-type AGN hosts in our sample have circumnuclear dust, while dust is only observed in 26% (9) of a pair-matched sample of 34 early-type, inactive galaxies. This result demonstrates a strong correlation between the presence of circumnuclear dust and accretion onto the central, supermassive black hole in elliptical and lenticular galaxies. This correlation is not present at later Hubble types, where a sample of 31 active and 31 inactive galaxies all contain circumnuclear dust. These archival, Hubble Space Telescope observations reveal a wide range of mostly chaotic dust morphologies. Current estimates suggest the dust settling or destruction time is on order of 108 yr, and therefore the presence of dust in ~50% of early-type galaxies requires frequent replenishment and similarly frequent fueling of their central supermassive black holes. The observed dust could be internally produced (via stellar winds) or externally accreted, although there are observational challenges for both of these scenarios. Our analysis also reveals that approximately one-third of the early-type galaxies without circumnuclear dust have nuclear stellar disks. These nuclear stellar disks may provide a preferred kinematic axis to externally accreted material, and this material may in turn form new stars in these disks. The observed incidence of nuclear stellar disks and circumnuclear dust suggests that episodic replenishment of nuclear stellar disks occurs and is approximately concurrent with the fueling of the central AGN.
[ Tran et al. 2001. AJ, 121, 2928. ]
We examine the dust properties of a nearby distance-limited sample of early-type galaxies using WFPC2 of the Hubble Space Telescope. Dust is detected in 29 out of 67 galaxies (43%), including 12 with small nuclear dusty disks. In a separate sample of 40 galaxies biased for the detection of dust by virtue of their detection in IRAS 100 μm band, dust is found in ~78% of the galaxies, 15 of which contain dusty disks. In those galaxies with detectable dust, the apparent mass of the dust correlates with radio and far-infrared luminosity, becoming more significant for systems with filamentary dust. A majority of IRAS and radio detections are also associated with dusty galaxies rather than dustless galaxies. This indicates that thermal emission from clumpy, filamentary dust is the main source of the far-IR radiation in early-type galaxies. Dust in small disklike morphology tends to be well aligned with the major axis of the host galaxies, while filamentary dust appears to be more randomly distributed with no preference for alignment with any major galactic structure. This suggests that, if the dusty disks and filaments have a common origin, the dust originates externally and requires time to dynamically relax and settle in the galaxy potential in the form of compact disks. More galaxies with visible dust than without dust display emission lines, indicative of ionized gas, although such nuclear activity does not show a preference for dusty disk over filamentary dust. There appears to be a weak relationship between the mass of the dusty disks and central velocity dispersion of the galaxy, suggesting a connection with a similar recently recognized relationship between the latter and the black hole mass. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.
성간분자운(interstellar molecular clouds; cold dard clouds)의 중력수축에 의한 계층적 분화를 통해 별의 씨앗인 고밀도 분자운핵(dense cores)들이 형성되고, 이후 계속된 질량 유입(mass accretion)과 중력 수축에 의해서 최종적으로 별이 형성된다고 알려져 있다. 최근 허셜우주망원경(Herschel Space Observatory)의 관측결과에 의해 이들 성간분자운이 모두 필라멘트 구조(filamentary structures; filaments)를 갖고 있으며, 필라멘트 구조가 고밀도 분자운핵과 별의 생성에 중요한 역할을 담당하고 있음이 밝혀졌다. 이번 저널클럽에서는 지난 2013년에 열린 Protostars and Planets VI 학회 발표논문집에 실린 André et al. (2014) "From Filamentary Networks to Dense Cores in Molecular Clouds: Toward a New Paradigm for Star Formation" 논문의 내용 중 Secsion 2. UNIVERSALITY OF THE FILAMENTARY STRUCTURE OF THE COLD ISM 부분을 바탕으로 필라멘트 구조에 대한 관측 결과에 대해 이야기를 나누고자 한다.
Abstract (reference): Recent studies of the nearest star-forming clouds of the Galaxy at submillimeter wavelengths with the Herschel Space Observatory have provided us with unprecedented images of the initial and boundary conditions of the star-formation process. The Herschel results emphasize the role of interstellar filaments in the star-formation process and connect remarkably well with nearly a decade’s worth of numerical simulations and theory that have consistently shown that the interstellar medium (ISM) should be highly filamentary on all scales, and star formation is intimately related to self-gravitating filaments. In this review, we trace how the apparent complexity of cloud structure and star formation is governed by relatively simple universal processes — from filamentary clumps to galactic scales. We emphasize two crucial and complementary aspects: (1) the key observational results obtained with Herschel over the past three years, along with relevant new results obtained from the ground on the kinematics of interstellar structures; and (2) the key existing theoretical models and the many numerical simulations of interstellar cloud structure and star formation. We then synthesize a comprehensive physical picture that arises from the confrontation of these observations and simulations.
1) User interface automation, launching programs, file management, text processing, custom dialogs, internet functions, web page automation, Excel automation, database/XML/CSV functions, regular expressions, VBScript, C#.
2) Many triggers, including hotkeys, mouse, window, autotext, scheduler, toolbars and menus.
- Records keyboard and mouse actions.
3) Captures, finds and clicks web page objects, other UI objects, on-screen images and text.
4) Programming language with functions, classes, full dll/API/COM support.
5) You can create programs for various purposes. Run in Quick Macros or as exe files.
1) SN Ia 를 이용한 Dark Energy 발견 연구 소개 (2011 노벨상)
- SN Ia 의 특성과 이를 표준촉광으로 사용한 가속팽창 연구 내용?
- SN Ia 를 표준촉광으로 사용하기 위한 가정 및 연구의 특수성
2) SN Ia 가 표준촉광으로 활용 가능/불가능 에 관한 최근 연구 소개
- 노벨상 연구팀: 은하 진화와 SN Ia 광도는 무관
- 최근 연구: 은하의 age 또는 metallicity 에 따른 SN Ia 광도 차이 발견
3) 현대우주론에서 SN Ia 연구가 가지는 의미
4) SN Ia 이외의 우주가속팽창(Dark Energy 존재) 증거
- CMB power spectrum (structure of CMB peaks change)?
- ISW (about Gravitational well of galaxy supercluster)
star-galaxy separation은 전천후 측광 관측 데이터에서 좋은 galaxy (또는 star, quasar 등) catalogue를 만드는데 중요한 이슈이다.
기존에 주로 쓰이던 방법(& 이것의 문제점) 및 최근에 제안된 방법을 소개하고, 몇가지 데이터(SDSS, HSC, DECaLS)에 대해 진행된 star-galaxy separation을 담은 논문들의 일부를 소개한다.
The SDSS photometric pipeline performs a morphological star/galaxy separation. The quality of this separation is therefore intimately related to the seeing and sky brightness. Photo's classifications have been tested against those of the COMBO survey (which effectively uses low-resolution spectroscopy for star/galaxy separation) in a region of the sky that both surveys have scanned. While the comparison was carried out for DR1 data, the DR2/DR3 data are not significantly different.
The classificaiton_extendedness? parameter, which is based on the difference between the CModel and PSF magnitudes, is stored in the database and is a reasonable star/galaxy classifier. Using the star/galaxy separation from HST/ACS in COSMOS as the truth table, here we characterize the accuracy of our star/galaxy separation. The completeness is defined as a fraction of ACS stars properly classified as stars in HSC. The contamination is a fraction of ACS galaxies among objects classified as stars in HSC. Both the completeness and contamination rates are strong function of the seeing size and depth.
The mergers of galaxy clusters are the most energetic events in the universe after the Big Bang. With the increased availability of multi-object spectroscopy and X-ray data an ever increasing fraction of local clusters are recognised as exhibiting signs of recent or past merging events on various scales. Our goal is to probe how these mergers affect the evolution and content of their member galaxies. We specifically aim to answer the following questions: Is the quenching of star formation in merging clusters enhanced when compared with relaxed clusters? Is the quenching preceded by a (short lived) burst of star formation? We obtained optical spectroscopy of >400 galaxies in the field of the merging cluster Abell 520. We combine these observations with archival data to get a comprehensive picture of the state of star formation in the members of this merging cluster. Finally, we compare these observations with a control sample of 10 non-merging clusters at the same redshift from The Arizona Cluster Redshift Survey (ACReS). We split the member galaxies in passive, star forming or recently quenched depending on their spectra. The core of the merger shows a decreased fraction of star forming galaxies compared to clusters in the non-merging sample. This region, dominated by passive galaxies, is extended along the axis of the merger. We find evidence of rapid quenching of the galaxies during the core passage with no signs of a star burst on the time scales of the merger (~0.4Gyr). Additionally, we report the tentative discovery of an infalling group along the main filament feeding the merger, currently at ~2.5 Mpc from the merger centre. This group contains a high fraction of star forming galaxies as well as ~2/3 of all the recently quenched galaxies in our survey.
Shells are low surface brightness tidal debris that appear as interleaved caustics with large opening angles, often situated on both sides of the galaxy center. In this paper, we study the incidence and formation processes of shell galaxies in the cosmological gravity+hydrodynamics Illustris simulation. We identify shells at redshift z=0 using stellar surface density maps, and we use stellar history catalogs to trace the birth, trajectory and progenitors of each individual star particle contributing to the tidal feature. Out of a sample of the 220 most massive galaxies in Illustris (M200crit > 6 × 1012 M⊙), 18%±3% of the galaxies exhibit shells. This fraction increases with increasing mass cut: higher mass galaxies are more likely to have stellar shells. Furthermore, the fraction of massive galaxies that exhibit shells decreases with increasing redshift. We find that shell galaxies observed at redshift z = 0 form preferentially through relatively major mergers ( 1:10 in stellar mass ratio). Progenitors are accreted on low angular momentum orbits, in a preferred time-window between ∼4 and 8 Gyrs ago. Our study indicates that, due to dynamical friction, more massive satellites are allowed to probe a wider range of impact parameters at accretion time, while small companions need almost purely radial infall trajectories in order to produce shells. We also find a number of special cases, as a consequence of the additional complexity introduced by the cosmological setting. These include galaxies with multiple shell- forming progenitors, satellite-of-satellites also forming shells, or satellites that fail to produce shells due to multiple major mergers happening in quick succession.
Aims: 1156 + 295 is a flat-spectrum quasar that is loud at both radio and γ-ray wavelengths. Previous observations of the source revealed a radio morphology on pc to kpc scales consistent with a helical jet model. We carried out VLBA observations at centimeter and millimeter wavelengths to study the structure of the innermost jet and understand the relation between the helical structure and astrophysical processes in the central engine.
Methods: The source 1156 + 295 was observed with the VLBA at 86, 43, and 15 GHz at four epochs from 10 May 2003 to 13 March 2005. The observations were carried out in a full polarization mode. The highest resolution of the observations is 0.08 mas (~0.5 pc) at 86 GHz.
Results: A core-jet structure with six jet components is identified in 1156 + 295. Three jet components are detected for the first time. The apparent transverse velocities of the six jet components derived from proper motion measurements range between 3.6 c and 11.6 c, suggesting that highly relativistic jet plasma moves in the direction close to the line of sight. The overall jet has an oscillating morphology with multiple curvatures on pc scales, which might be indicative of a helical pattern. Models of a helical jet are discussed in the context of both Kelvin-Helmholtz (K-H) instability and jet precession. The K-H instability model is in closer agreement with the observed data.
Conclusions: The overall radio structure on scales from sub-pc to kpc appears to be fitted with a hydrodynamic model in the fundamental helical mode of Kelvin-Helmholtz (K-H) instability. This helical mode with an initial characteristic wavelength of λ0 = 0.2 pc is excited at the base of the jet on the scale of 0.005 pc (or 103Rs, the typical size of the broad line region of a supermassive black hole of 4.3 × 108 M⊙). A precessing jet model can also fit the observed jet structure on scales of between 10 pc and 300 pc. However, with the precessing jet model, additional astrophysical processes may be required to explain the bendings of the inner jet structure (1 to 10 pc) and re-collimation of the large-scale jet outflow (>300 pc).
The deep connection between galaxies and their supermassive black holes is central to modern astrophysics and cosmology. The observed correlation between galaxy and black hole mass is usually attributed to the contribution of major mergers to both. We make use of a sample of galaxies whose disk-dominated morphologies indicate a major-merger-free history and show that such systems are capable of growing supermassive black holes at rates similar to quasars. Comparing black hole masses to conservative upper limits on bulge masses, we show that the black holes in the sample are typically larger than expected if processes creating bulges are also the primary driver of black hole growth. The same relation between black hole and total stellar mass of the galaxy is found for the merger-free sample as for a sample which has experienced substantial mergers, indicating that major mergers do not play a significant role in controlling the coevolution of galaxies and black holes. We suggest that more fundamental processes which contribute to galaxy assembly are also responsible for black hole growth.
1) 연구원 실적 관리 시스템
- 개인업적평가 저널 분류 기준 (이전 년도 논문 등급을 JCR 기준으로 분류)
- 연구관리시스템 (실적 검색 관련 팁)
2) 한국천문학회 수상 : 젊은 천문학자상, 우수논문상, 샛별상, 우수포스터상
3) 한국우주과학회 수상 : 두진 우주과학자상, 신진 우주과학자상, SELab상
4) 한국천문연구원 논문상 : 학생논문상 (SCI 기준 주저자 1~1.5편, 40점 이상)
5) 학생 연구원으로서 개인 실적 관리
6) 연구원 실적 평가 시스템의 문제점 (정량 평가의 문제점)