scholarly journals A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE)

2019 ◽  
Vol 623 ◽  
pp. A52 ◽  
Author(s):  
A. Boselli ◽  
M. Fossati ◽  
A. Longobardi ◽  
G. Consolandi ◽  
P. Amram ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Narrow Band ◽  
Elliptical Galaxy ◽  
Virgo Cluster ◽  
Environmental Survey ◽  
Narrow Band Image ◽  
The North ◽  
Optical Images ◽  
The Galaxy ◽  
North Western

We observed the giant elliptical galaxy M 87 during the Virgo Environmental Survey Tracing Galaxy Evolution (VESTIGE), a blind narrow-band Hα+[NII] imaging survey of the Virgo cluster carried out with MegaCam at the Canada French Hawaii Telescope (CFHT). The deep narrow-band image confirmed the presence of a filament of ionised gas extending up to ≃3 kpc in the north-western direction and ≃8 kpc to the southeast, with a couple of plumes of ionised gas, the weakest of which, at ≃18 kpc from the nucleus, was previously unknown. The analysis of deep optical images taken from the NGVS survey confirms that this gas filament is associated with dust seen in absorption which is now detected up to ≃2.4 kpc from the nucleus. We also analysed the physical and kinematical properties of the ionised gas filament using deep IFU MUSE data covering the central 4.8 × 4.8 kpc2 of the galaxy. The spectroscopic data confirm a perturbed kinematics of the ionised gas, with differences in velocity of ≃700–800 km s−1 on scales of ≲1 kpc. The analysis of 2D diagnostic diagrams and the observed relationship between the shock-sensitive [OI]/Hα line ratio and the velocity dispersion of the gas suggest that the gas is shock-ionised.

scholarly journals A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE)

2018 ◽  
Vol 620 ◽  
pp. A164 ◽  
Author(s):  
A. Boselli ◽  
M. Fossati ◽  
G. Consolandi ◽  
P. Amram ◽  
C. Ge ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Narrow Band ◽  
Virgo Cluster ◽  
X Rays ◽  
Environmental Survey ◽  
North West ◽  
The North ◽  
Ram Pressure ◽  
The Galaxy

We observed the late-type peculiar galaxy NGC 4424 during the Virgo Environmental Survey Tracing Galaxy Evolution (VESTIGE), a blind narrow-band Hα+[NII] imaging survey of the Virgo cluster carried out with MegaCam at the Canada-French-Hawaii Telescope (CFHT). The presence of a ∼110 kpc (in projected distance) HI tail in the southern direction indicates that this galaxy is undergoing a ram pressure stripping event. The deep narrow-band image revealed a low surface brightness (Σ(Hα) ≃ 4 × 10−18 erg s−1 cm−2 arcsec−2) ionised gas tail ∼10 kpc in length extending from the centre of the galaxy to the north-west, thus in the direction opposite to the HI tail. Chandra and XMM X-rays data do not show a compact source in the nucleus or an extended tail of hot gas, while IFU spectroscopy (MUSE) indicates that the gas is photo-ionised in the inner regions and shock-ionised in the outer parts. Medium-resolution (MUSE) and high-resolution (Fabry-Perot) IFU spectroscopy confirms that the ionised gas is kinematically decoupled from the stellar component and indicates the presence of two kinematically distinct structures in the stellar disc. The analysis of the SED of the galaxy indicates that the activity of star formation was totally quenched in the outer disc ∼250–280 Myr ago, while only reduced by ∼80% in the central regions. All this observational evidence suggests that NGC 4424 is the remnant of an unequal-mass merger that occurred ≲500 Myr ago when the galaxy was already a member of the Virgo cluster, and is now undergoing a ram pressure stripping event that has removed the gas and quenched the activity of star formation in the outer disc. The tail of ionised gas probably results from the outflow produced by a central starburst fed by the collapse of gas induced by the merging episode. This outflow is sufficiently powerful to overcome the ram pressure induced by the intracluster medium on the disc of the galaxy crossing the cluster. This analysis thus suggests that feedback can participate in the quenching process of galaxies in high-density regions.

scholarly journals A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE)

2018 ◽  
Vol 615 ◽  
pp. A114 ◽  
Author(s):  
A. Boselli ◽  
M. Fossati ◽  
J. C. Cuillandre ◽  
S. Boissier ◽  
M. Boquien ◽  
...  
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Narrow Band ◽  
Spectral Energy Distribution ◽  
Far Infrared ◽  
Extreme Environment ◽  
Virgo Cluster ◽  
Spectral Energy ◽  
Environmental Survey ◽  
The Galaxy

During pilot observations of the Virgo Environmental Survey Tracing Galaxy Evolution (VESTIGE), a blind narrow-band Hα + [NII] imaging survey of the Virgo cluster carried out with MegaCam at the CFHT, we have observed the spiral galaxy NGC 4254 (M99). Deep Hα + [NII] narrow-band and GALEX UV images reveal the presence of 60 compact (70–500 pc radius) star-forming regions up to ≃20 kpc outside the optical disc of the galaxy. These regions are located along a tail of HI gas stripped from the disc of the galaxy after a rapid gravitational encounter with another Virgo cluster member that simulations indicate occurred 280–750 Myr ago. We have combined the VESTIGE data with multifrequency data from the UV to the far-infrared to characterise the stellar populations of these regions and study the star formation process in an extreme environment such as the tails of stripped gas embedded in the hot intracluster medium. The colour, spectral energy distribution (SED), and linear size consistently indicate that these regions are coeval and have been formed after a single burst of star formation that occurred ≲100 Myr ago. These regions might become free floating objects within the cluster potential well, and be the local analogues of compact sources produced after the interaction of gas-rich systems that occurred during the early formation of clusters.

scholarly journals Revising the merger scenario of the galaxy cluster Abell 1644: a new gas poor structure discovered by weak gravitational lensing

2020 ◽  
Vol 495 (2) ◽  
pp. 2007-2021 ◽  
Author(s):  
R Monteiro-Oliveira ◽  
L Doubrawa ◽  
R E G Machado ◽  
G B Lima Neto ◽  
M Castejon ◽  
...  
Keyword(s):  
Gravitational Lensing ◽  
Elliptical Galaxy ◽  
Galaxy Cluster ◽  
X Ray ◽  
The North ◽  
Density Maps ◽  
Hydrodynamical Simulation ◽  
The Galaxy ◽  
Maximum Separation ◽  
Comprehensive Study

ABSTRACT The galaxy cluster Abell 1644 ($\bar{z}=0.047$) is known for its remarkable spiral-like X-ray emission. It was previously identified as a bimodal system, comprising the subclusters, A1644S and A1644N, each one centred on a giant elliptical galaxy. In this work, we present a comprehensive study of this system, including new weak lensing and dynamical data and analysis plus a tailor-made hydrodynamical simulation. The lensing and galaxy density maps showed a structure in the North that could not be seen on the X-ray images. We, therefore, rename the previously known northern halo as A1644N1 and the new one as A1644N2. Our lensing data suggest that those have fairly similar masses: $M_{200}^{\rm N1}=0.90_{-0.85}^{+0.45} \times 10^{14}$ and $M_{200}^{\rm N2}=0.76_{-0.75}^{+0.37} \times 10^{14}$ M⊙, whereas the southern structure is the main one: $M_{200}^{\rm S}=1.90_{-1.28}^{+0.89}\times 10^{14}$ M⊙. Based on the simulations, fed by the observational data, we propose a scenario where the remarkable X-ray characteristics in the system are the result of a collision between A1644S and A1644N2 that happened ∼1.6 Gyr ago. Currently, those systems should be heading to a new encounter, after reaching their maximum separation.

scholarly journals Secularly powered outflows from AGNs: the dominance of non-merger driven supermassive black hole growth

2019 ◽  
Vol 489 (3) ◽  
pp. 4016-4031 ◽  
Author(s):  
R J Smethurst ◽  
B D Simmons ◽  
C J Lintott ◽  
J Shanahan
Keyword(s):  
Black Hole ◽  
Galaxy Evolution ◽  
Narrow Band ◽  
Narrow Band Imaging ◽  
Black Hole Accretion ◽  
Accretion Rates ◽  
The Galaxy ◽  
Black Hole Growth ◽  
Outflow Rate ◽  
Hole Growth

ABSTRACT Recent observations and simulations have revealed the dominance of secular processes over mergers in driving the growth of both supermassive black holes (SMBHs) and galaxy evolution. Here, we obtain narrow-band imaging of AGN powered outflows in a sample of 12 galaxies with disc-dominated morphologies, whose history is assumed to be merger-free. We detect outflows in 10/12 sources in narrow-band imaging of the $\mathrm{[O\, \small {III}] }$ $5007~\mathring{\rm A}$ emission using filters on the Shane-3m telescope. We calculate a mean outflow rate for these AGNs of $0.95\pm 0.14~\rm {M}_{\odot }~\rm {yr}^{-1}$. This exceeds the mean accretion rate of their SMBHs ($0.054\pm 0.039~\rm {M}_{\odot }~\rm {yr}^{-1}$) by a factor of 18. Assuming that the galaxy must provide at least enough material to power both the AGN and outflow, this gives a lower limit on the average inflow rate of $1.01\pm 0.14~\rm {M}_{\odot }~\rm {yr}^{-1}$, a rate which simulations show can be achieved by bars, spiral arms, and cold accretion. We compare our disc-dominated sample to a sample of nearby AGNs with merger dominated histories and show that the black hole accretion rates in our sample are five times higher (4.2σ) and the outflow rates are five times lower (2.6σ). We suggest that this could be a result of the geometry of the smooth, planar inflow in a secular dominated system, which is both spinning up the black hole to increase accretion efficiency and less affected by feedback from the outflow, than in a merger-driven system with chaotic quasi-spherical inflows. This work provides further evidence that secular processes are sufficient to fuel SMBH growth.

scholarly journals M87 Supermassive Black Hole Review

2021 ◽  
Author(s):  
Mekhala Ganguly
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Gravitational Lensing ◽  
Elliptical Galaxy ◽  
Virgo Cluster ◽  
Supermassive Black Hole ◽  
Cluster Of Galaxies ◽  
Hot Plasma ◽  
The Galaxy ◽  
Relativistic Particles

M87 is a giant elliptical galaxy in the Virgo cluster of galaxies. The radio source has a core which coincides with the nucleus of the galaxy and a jet of emission which is detected from radio to X-ray bands. A supermassive black hole is assumed to be at the centre of M87 which sends out relativistic particles in the form jets along its axis of rotation. Relativistic particles accelerated in a magnetic field, give out synchrotron radiation. The centre is surrounded by an accretion disc, which is the closest that we can probe into a black hole. High resolution observations are needed to examine the nature of the radio emission closest to the centre of M87. An array of millimetre-band telescopes across the globe were used as an interferometer, called the Event Horizon Telescope, (EHT) to probe the nuclear region. The angular resolution of this interferometer array is 25 microarc sec, at a wavelength of 1.3mm and the data was carefully calibrated and imaged. The resulting image shows an asymmetric ring which is consistent with the predictions of strong gravitational lensing of synchrotron emission from hot plasma near the event horizon. In this paper, we review the results of the observations of the radio galaxy, M87, using the Event Horizon Telescope

scholarly journals The Gravitational Field of the Galaxy in the Z Direction

1977 ◽  
Vol 4 (2) ◽  
pp. 65-66
Author(s):  
R. F. Griffin
Keyword(s):  
Galactic Plane ◽  
Narrow Band ◽  
Radial Velocities ◽  
Photoelectric Photometry ◽  
Giant Stars ◽  
The North ◽  
The Galaxy ◽  
Absolute Magnitudes ◽  
North Galactic ◽  
K Giants

This is a progress report of a project designed to find the component, perpendicular to the Galactic plane, of the gravitational potential of the Galaxy. The principle is to measure the radial velocities and distances of a large number of K-giant stars near the North Galactic Pole. My student G. A. Radford is masterminding the project; collaborating with us are Drs. J. E. Gunn of the Hale Observatories and L. Hansen and K. Gyldenkerne of Copenhagen.We have measured the radial velocities of all the HD stars of type KO and later, and many of the G5 stars, within 15°of the Galactic Pole, using the Cambridge photoelectric spectrometer. In addition, we have observed all the stars classified as K giants by Upgren in his declination zones 25° to 31°, using the spectrometer on the Hale telescope. There are about 900 stars observed altogether, including about 200 Upgren stars, running down to twelfth magnitude or so, which are not in the Henry Draper Catalogue. To determine the distances of all these stars we are now trying to determine the absolute magnitudes by narrow-band photoelectric photometry in the Copenhagen system. Most of the observations have been made, thanks largely to the very generous grants of observing time given by the Hale Observatories earlier this year; but the reductions have only been completed for about 300 stars (including 244 K giants) which were observed last year at Kitt Peak, and the present, very preliminary, discussion is based on those stars alone.

scholarly journals Extraplanar gas and magnetic fields in the cluster spiral galaxy NGC 4569

2006 ◽  
Vol 2 (S237) ◽  
pp. 470-470
Author(s):  
S. Ryś ◽  
K. T. Chyży ◽  
M. Weżgowiec ◽  
M. Ehle ◽  
R. Beck
Keyword(s):  
Magnetic Fields ◽  
Galaxy Evolution ◽  
Spiral Galaxy ◽  
Virgo Cluster ◽  
X Ray ◽  
Gas Phases ◽  
Hot Gas ◽  
The Core ◽  
The Galaxy ◽  
Galaxy Disk

AbstractThe Virgo Cluster spiral NGC 4569 is known for its compact starburst in the core and unusual outflow of Hα emitting gas perpendicular to the galaxy disk. Recent radio polarimetric observations with the Effelsberg telescope reveal huge magnetized outflows. Preliminary results of our XMM-Newton observations uncover not only hot gas in the disk but also an extensive X-ray envelope around it. We investigate the possibility of starburst-induced galactic outflows in various gas phases and cluster influence on the galaxy evolution.

scholarly journals A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE)

2018 ◽  
Vol 614 ◽  
pp. A57 ◽  
Author(s):  
M. Fossati ◽  
J. T. Mendel ◽  
A. Boselli ◽  
J. C. Cuillandre ◽  
B. Vollmer ◽  
...  
Keyword(s):  
Major Axis ◽  
Virgo Cluster ◽  
Monte Carlo Code ◽  
Gas Stripping ◽  
Gas Emission ◽  
Filamentary Structure ◽  
Environmental Survey ◽  
Star Forming ◽  
Very Large Telescope ◽  
The Galaxy

The Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE) is a blind narrow-band Hα + [NII] imaging survey carried out with MegaCam at the Canada-France-Hawaii Telescope. During pilot observations taken in the spring of 2016 we observed NGC 4330, an intermediate mass (M* ≃ 109.8 M⊙) edge-on star forming spiral currently falling into the core of the Virgo cluster. While previous Hα observations showed a clumpy complex of ionised gas knots outside the galaxy disc, new deep observations revealed a low surface brightness ~10 kpc tail exhibiting a peculiar filamentary structure. The filaments are remarkably parallel to one another and clearly indicate the direction of motion of the galaxy in the Virgo potential. Motivated by the detection of these features which indicate ongoing gas stripping, we collected literature photometry in 15 bands from the far-UV to the far-IR and deep optical long-slit spectroscopy using the FORS2 instrument at the ESO Very Large Telescope. Using a newly developed Monte Carlo code that jointly fits spectroscopy and photometry, we reconstructed the star formation histories in apertures along the major axis of the galaxy. Our results have been validated against the output of CIGALE, a fitting code which has been previously used for similar studies. We found a clear outside-in gradient with radius of the time when the quenching event started: the outermost radii were stripped ~500 Myr ago, while the stripping reached the inner 5 kpc from the centre in the last 100 Myr. Regions at even smaller radii are currently still forming stars fueled by the presence of HI and H2 gas. When compared to statistical studies of the quenching timescales in the local Universe we find that ram pressure stripping of the cold gas is an effective mechanism to reduce the transformation times for galaxies falling into massive clusters. Future systematic studies of all the active galaxies observed by VESTIGE in the Virgo cluster will extend these results to a robust statistical framework.

scholarly journals Star-forming Dwarf Galaxies in Filamentary Structures around the Virgo Cluster: Probing Chemical Pre-processing in Filament Environments

2021 ◽  
Vol 923 (2) ◽  
pp. 235
Author(s):  
Jiwon Chung ◽  
Suk Kim ◽  
Soo-Chang Rey ◽  
Youngdae Lee
Keyword(s):  
Star Formation ◽  
Galaxy Evolution ◽  
Dwarf Galaxies ◽  
Formation Rate ◽  
Chemical Properties ◽  
Local Environment ◽  
Stellar Mass ◽  
Virgo Cluster ◽  
Star Forming ◽  
The Galaxy

Abstract It has been proposed that the filament environment is closely connected to the pre-processing of galaxies, where their properties may have been changed by environmental effects in the filament before they fell into the galaxy cluster. We present the chemical properties of star-forming dwarf galaxies (SFDGs) in five filamentary structures (Virgo III, Leo Minor, Leo II A, Leo II B, and Canes Venatici) around the Virgo cluster using the Sloan Digital Sky Survey optical spectroscopic data and Galaxy Evolution Explorer ultraviolet photometric data. We investigate the relationship between stellar mass, gas-phase metallicity, and specific star formation rate (sSFR) of the SFDGs in the Virgo filaments in comparison to those in the Virgo cluster and field. We find that, at a given stellar mass, SFDGs in the Virgo filaments show lower metallicity and higher sSFR than those in the Virgo cluster on average. We observe that SFDGs in the Virgo III filament show enhanced metallicities and suppressed star formation activities comparable to those in the Virgo cluster, whereas SFDGs in the other four filaments exhibit similar properties to the field counterparts. Moreover, about half of the galaxies in the Virgo III filament are found to be morphologically transitional dwarf galaxies that are supposed to be on the way to transforming into quiescent dwarf early-type galaxies. Based on the analysis of the galaxy perturbation parameter, we propose that the local environment represented by the galaxy interactions might be responsible for the contrasting features in chemical pre-processing found in the Virgo filaments.

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