Recovering the origin of the lenticular galaxy NGC3115 using multi-band photometry

2019 ◽  
Vol 15 (S359) ◽  
pp. 421-423
Author(s):  
Maria Luísa Buzzo ◽  
Arianna Cortesi ◽  
Ariel Werle ◽  
Claudia Mendes de Oliveira
Keyword(s):  
Stellar Population ◽  
Galactic Nuclei ◽  
Two Phase ◽  
Thick Disc ◽  
Star Formation Activity ◽  
The Galaxy ◽  
Minor Mergers ◽  
Main Components ◽  
Baryonic Mass ◽  
Multi Band

AbstractWe perform simultaneous multi-band fitting, using the routine GALFITM, of the galaxy NGC3115, in order to recover the stellar populations of its main components (a bulge, a thin disc and a thick disc). We model 11 bands, from ultraviolet to infrared, in order to take into account the galaxy younger stellar population and the presence of the Active Galactic Nuclei (AGN). We find that the majority of the galaxy baryonic mass belongs to the thick disc, which is also the oldest galaxy component, consistent with results from the literature. Differently from previous works, we find that the bulge has the bluest colour and it is younger than the thick disc, either as a result of recent star formation activity, or AGN feedback, or white dwarf emission in an old stellar population. Finally, we propose that NGC3115 was formed either through a two-phase formation scenario, or via an outside-in quenching of an isolated spiral galaxy, whose thick disc had been heated-up via minor mergers with dwarf satellites.

scholarly journals Star formation at the Galactic Centre: coevolution of multiple young stellar discs

2019 ◽  
Vol 490 (4) ◽  
pp. 5820-5831 ◽  
Author(s):  
Alessandra Mastrobuono-Battisti ◽  
Hagai B Perets ◽  
Alessia Gualandris ◽  
Nadine Neumayer ◽  
Anna C Sippel
Keyword(s):  
Star Formation ◽  
Stellar Population ◽  
Direct Evidence ◽  
Galactic Nuclei ◽  
Galactic Centre ◽  
Stellar Clusters ◽  
Stellar Disc ◽  
The Galaxy ◽  
Kinematic Properties

ABSTRACT Studies of the Galactic Centre suggest that in situ star formation may have given rise to the observed stellar population near the central supermassive black hole (SMBH). Direct evidence for a recent starburst is provided by the currently observed young stellar disc (2–7 Myr) in the central 0.5 pc of the Galaxy. This result suggests that star formation in galactic nuclei may occur close to the SMBH and produce initially flattened stellar discs. Here, we explore the possible build-up and evolution of nuclear stellar clusters near SMBHs through in situ star formation producing stellar discs similar to those observed in the Galactic Centre and other nuclei. We use N-body simulations to model the evolution of multiple young stellar discs and explore the potential observable signatures imprinted by such processes. Each of the five simulated discs is evolved for 100 Myr before the next one is introduced in the system. We find that populations born at different epochs show different morphologies and kinematics. Older and presumably more metal-poor populations are more relaxed and extended, while younger populations show a larger amount of rotation and flattening. We conclude that star formation in central discs can reproduce the observed properties of multiple stellar populations in galactic nuclei differing in age, metallicity, and kinematic properties.

scholarly journals The Disc Origin of the Milky Way Bulge

2016 ◽  
Vol 33 ◽  
Author(s):  
P. Di Matteo
Keyword(s):  
Milky Way ◽  
Complex Structure ◽  
Galactic Bulge ◽  
Galactic Disc ◽  
Major Step ◽  
Thick Disc ◽  
Global Properties ◽  
Out Of Plane ◽  
The Galaxy ◽  
Main Components

AbstractThe Galactic bulge, that is the prominent out-of-plane over-density present in the inner few kiloparsecs of the Galaxy, is a complex structure, as the morphology, kinematics, chemistry, and ages of its stars indicate. To understand the nature of its main components—those at [Fe/H] ≳ −1 dex—it is necessary to make an inventory of the stellar populations of the Galactic disc(s), and of their borders: the chemistry of the disc at the solar vicinity, well known from detailed studies of stars over many years, is not representative of the whole disc. This finding, together with the recent revisions of the mass and sizes of the thin and thick discs, constitutes a major step in understanding the bulge complexity. N-body models of a boxy-/peanut-shaped bulge formed from a thin disc through the intermediary of a bar have been successful in interpreting a number of global properties of the Galactic bulge, but they fail in reproducing the detailed chemo-kinematic relations satisfied by its components and their morphology. It is only by adding the thick disc to the picture that we can understand the nature of the Galactic bulge.

scholarly journals Larger λR in the disc of isolated active spiral galaxies than in their non-active twins

2020 ◽  
Vol 639 ◽  
pp. L9 ◽  
Author(s):  
I. del Moral-Castro ◽  
B. García-Lorenzo ◽  
C. Ramos Almeida ◽  
T. Ruiz-Lara ◽  
J. Falcón-Barroso ◽  
...  
Keyword(s):  
Spiral Galaxies ◽  
Galactic Nuclei ◽  
Active Galaxies ◽  
Nuclear Activity ◽  
Spin Parameter ◽  
The Galaxy ◽  
Minor Mergers ◽  
Stellar Masses ◽  
The Universe ◽  
Rule Out

We present a comparison of the spin parameter λR, measured in a region dominated by the galaxy disc, between 20 pairs of nearby (0.005 <  z <  0.03) seemingly isolated twin galaxies differing in nuclear activity. We find that 80−82% of the active galaxies show higher values of λR than their corresponding non-active twin(s), indicating larger rotational support in the active galactic nuclei (AGN) discs. This result is driven by the 11 pairs of unbarred galaxies, for which 100% of the AGN show larger λR than their twins. These results can be explained by a more efficient angular momentum transfer from the inflowing gas to the disc baryonic matter in the case of the active galaxies. This gas inflow could have been induced by disc or bar instabilities, although we cannot rule out minor mergers if these are prevalent in our active galaxies. This result represents the first evidence of galaxy-scale differences between the dynamics of active and non-active isolated spiral galaxies of intermediate stellar masses (1010 <  M* <  1011 M⊙) in the Universe.

scholarly journals Reviving old controversies: is the early Galaxy flat or round?

2020 ◽  
Vol 636 ◽  
pp. A115 ◽  
Author(s):  
P. Di Matteo ◽  
M. Spite ◽  
M. Haywood ◽  
P. Bonifacio ◽  
A. Gómez ◽  
...  
Keyword(s):  
Stellar Population ◽  
Milky Way ◽  
Galactic Disc ◽  
Chemical Abundances ◽  
First Stars ◽  
Thick Disc ◽  
Large Program ◽  
The Galaxy ◽  
Early Galaxy ◽  
Two Populations

We analysed a set of very metal-poor stars, for which accurate chemical abundances have been obtained as part of the ESO Large Program “First stars” in the light of the Gaia DR2 data. The kinematics and orbital properties of the stars in the sample show they probably belong to the thick disc, partially heated to halo kinematics, and to the accreted Gaia Sausage-Enceladus satellite. The continuity of these properties with stars at both higher ([Fe/H] >  −2) and lower metallicities ([Fe/H] <  −4.) suggests that the Galaxy at [Fe/H] ≲ −0.5 and down to at least [Fe/H] ∼ −6 is dominated by these two populations. In particular, we show that the disc extends continuously from [Fe/H] ≤ −4 (where stars with disc-like kinematics have recently been discovered) up to [Fe/H] ≥ −2, the metallicity regime of the Galactic thick disc. An “ultra metal-poor thick disc” does indeed exist, constituting the extremely metal-poor tail of the canonical Galactic thick disc, and extending the latter from [Fe/H] ∼ −0.5 up to the most metal-poor stars discovered in the Galaxy to date. These results suggest that the disc may be the main, and possibly the only, stellar population that has formed in the Galaxy at these metallicities. This would mean that the dissipative collapse that led to the formation of the old Galactic disc must have been extremely fast. We also discuss these results in the light of recent simulation efforts made to reproduce the first stages of Milky Way-type galaxies.

scholarly journals An excessively massive thick disc of the enormous edge-on lenticular galaxy NGC 7572

2020 ◽  
Vol 493 (4) ◽  
pp. 5464-5478
Author(s):  
Anastasia V Kasparova ◽  
Ivan Yu Katkov ◽  
Igor V Chilingarian
Keyword(s):  
Stellar Population ◽  
Line Of Sight ◽  
Mass Ratio ◽  
Thick Disc ◽  
Novel Technique ◽  
The Galaxy ◽  
Depth Study ◽  
Formation And Evolution ◽  
Disc Galaxies ◽  
Disc Formation

ABSTRACT Galactic discs are known to have a complex multilayer structure. An in-depth study of the stellar population properties of the thin and thick components can elucidate the formation and evolution of disc galaxies. Even though thick discs are ubiquitous, their origin is still debated. Here we probe the thick disc formation scenarios by investigating NGC 7572, an enormous edge-on galaxy having R25 ≈ 25 kpc and Vrot ≈ 370 km s−1, which substantially exceeds the Milky Way size and mass. We analysed DECaLS archival imaging and found that the disc of NGC 7572 contains two flaring stellar discs (a thin and a thick disc) with similar radial scales. We collected deep long-slit spectroscopic data using the 6 m Russian BTA telescope and analysed them with a novel technique. We first reconstructed a non-parametric stellar line-of-sight velocity distribution along the radius of the galaxy and then fitted it with two kinematic components accounting for the orbital distribution of stars in thin and thick discs. The old thick disc turned out to be 2.7 times as massive as the intermediate-age thin component, 1.6 × 1011 M⊙ versus 5.9 × 1010 M⊙, which is very unusual. The different duration of the formation epochs evidenced by the [Mg/Fe] values of +0.3 and +0.15 dex for the thick and thin discs respectively, their kinematics, and the mass ratio suggest that in NGC 7572 we observe a rapidly formed very massive thick disc and an underdeveloped thin disc, whose growth ended prematurely due to the exhaustion of the cold gas likely because of environmental effects.

Stellar populations and ionised gas in central spheroidal galaxies

2020 ◽  
Vol 15 (S359) ◽  
pp. 469-472
Author(s):  
Vanessa Lorenzoni ◽  
Sandro B. Rembold
Keyword(s):  
Stellar Population ◽  
Synthesis Method ◽  
Galactic Nuclei ◽  
Stellar Populations ◽  
High Mass ◽  
Population Synthesis ◽  
The Galaxy ◽  
History Of ◽  
Low Mass ◽  
Spheroidal Galaxies

We investigate the stellar populations and ionised gas properties of a sample of central spheroidal galaxies in order to better constrain their history of star formation and gas excitation mechanism. We select galaxies from Spheroids Panchromatic Investigation in Different Environmental Regions (SPIDER) catalogue and separate these galaxies in different regimes of halo and galaxy mass. To characterise the stellar population properties of these galaxies we use the stellar population synthesis method with the Starlight code, and the presence of ionised gas is identified by measurements of the Hα equivalent width. We analyse how these properties behave as a function of the galaxy stellar mass and the parent halo mass. A trend is observed in the sense of increased ionised gas emission for low-mass centrals in high-mass halos. We interpret this trend in a scenario of intracluster medium (ICM) cooling versus active galactic nuclei (AGN) feedback in a Bondi accretion context.

The two-phase gas outflow in the Circinus Galaxy

2019 ◽  
Vol 15 (S359) ◽  
pp. 272-273
Author(s):  
M. A. Fonseca-Faria ◽  
A. Rodríguez-Ardila
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Temperature Sensitive ◽  
Ionized Gas ◽  
Two Phase ◽  
North West ◽  
Gas Kinematics ◽  
High Ionization ◽  
The Galaxy ◽  
Sensitive Line

AbstractWe employ Multi Unit Spectroscopic Explorer (MUSE) data to study the ionized and very ionized gas phase of the feedback in Circinus, the closest Seyfert 2 galaxy. The analysis of the nebular emission allowed us to detect a remarkable high-ionization gas outflow, out of the galaxy plane, traced by the coronal lines [Fe viii] 6089Å and [Fe x] 6374Å, extending up to 700 parsecs north-west from the nucleus. The gas kinematics reveal expanding gas shells with velocities of a few hundred km s-1, spatially coincident with prominent hard X-ray emission detected by Chandra. Density and temperature sensitive line ratios show that the extended high-ionization gas is characterized by a temperature of up to 18000 K and a gas density of ne > 102 cm−3. We propose two scenarios consistent with the observations to explain the high-ionization component of the outflow: an active galactic nuclei (AGN) ejection that took place ⁓105 yr ago or local gas excitation by shocks produced by the passage of a radio jet.

Statistical criteria of stellar population types

1966 ◽  
Vol 24 ◽  
pp. 101-110
Author(s):  
W. Iwanowska
Keyword(s):  
Stellar Population ◽  
Chemical Properties ◽  
Spectrophotometric Study ◽  
Physical And Chemical Properties ◽  
Population Type ◽  
The Galaxy ◽  
Distribution Parameters ◽  
Physical And Chemical ◽  
Statistical Criteria ◽  
And Chemical Properties

In connection with the spectrophotometric study of population-type characteristics of various kinds of stars, a statistical analysis of kinematical and distribution parameters of the same stars is performed at the Toruń Observatory. This has a twofold purpose: first, to provide a practical guide in selecting stars for observing programmes, second, to contribute to the understanding of relations existing between the physical and chemical properties of stars and their kinematics and distribution in the Galaxy.

The GLEAM 4-Jy Sample: The brightest radio-sources in the southern sky

2019 ◽  
Vol 15 (S356) ◽  
pp. 375-375
Author(s):  
Sarah White
Keyword(s):  
Radio Emission ◽  
Active Galactic Nuclei ◽  
Visual Inspection ◽  
Low Frequency ◽  
Galactic Nuclei ◽  
Radio Sources ◽  
Relativistic Jets ◽  
The Galaxy ◽  
Murchison Widefield Array ◽  
Past Activity

AbstractLow-frequency radio emission allows powerful active galactic nuclei (AGN) to be selected in a way that is unaffected by dust obscuration and orientation of the jet axis. It also reveals past activity (e.g. radio lobes) that may not be evident at higher frequencies. Currently, there are too few “radio-loud” galaxies for robust studies in terms of redshift-evolution and/or environment. Hence our use of new observations from the Murchison Widefield Array (the SKA-Low precursor), over the southern sky, to construct the GLEAM 4-Jy Sample (1,860 sources at S151MHz > 4 Jy). This sample is dominated by AGN and is 10 times larger than the heavily relied-upon 3CRR sample (173 sources at S178MHz > 10 Jy) of the northern hemisphere. In order to understand how AGN influence their surroundings and the way galaxies evolve, we first need to correctly identify the galaxy hosting the radio emission. This has now been completed for the GLEAM 4-Jy Sample – through repeated visual inspection and extensive checks against the literature – forming a valuable, legacy dataset for investigating relativistic jets and their interplay with the environment.

scholarly journals Probing the cool ISM in galaxies via 21 cm H i absorption

2012 ◽  
Vol 8 (S292) ◽  
pp. 188-188
Author(s):  
J. R. Allison ◽  
E. M. Sadler ◽  
S. J. Curran ◽  
S. N. Reeves
Keyword(s):  
Spectral Line ◽  
Active Galactic Nuclei ◽  
Large Scale ◽  
Galactic Nuclei ◽  
Host Galaxies ◽  
The Galaxy ◽  
Early Type Galaxy ◽  
Finding Method ◽  
Compact Array ◽  
Cold Gas

AbstractRecent targeted studies of associated H i absorption in radio galaxies are starting to map out the location, and potential cosmological evolution, of the cold gas in the host galaxies of Active Galactic Nuclei (AGN). The observed 21 cm absorption profiles often show two distinct spectral-line components: narrow, deep lines arising from cold gas in the extended disc of the galaxy, and broad, shallow lines from cold gas close to the AGN (e.g. Morganti et al. 2011). Here, we present results from a targeted search for associated H i absorption in the youngest and most recently-triggered radio AGN in the local universe (Allison et al. 2012b). So far, by using the recently commissioned Australia Telescope Compact Array Broadband Backend (CABB; Wilson et al. 2011), we have detected two new absorbers and one previously-known system. While two of these show both a broad, shallow component and a narrow, deep component (see Fig. 1), one of the new detections has only a single broad, shallow component. Interestingly, the host galaxies of the first two detections are classified as gas-rich spirals, while the latter is an early-type galaxy. These detections were obtained using a spectral-line finding method, based on Bayesian inference, developed for future large-scale absorption surveys (Allison et al. 2012a).

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