scholarly journals Star-forming complexes in the polar ring galaxy NGC660

2017 ◽  
Vol 26 (1) ◽  
Author(s):  
Ksenia I. Smirnova ◽  
Dmitri S. Wiebe ◽  
Alexei V. Moiseev
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Star Forming ◽  
Polar Ring ◽  
Star Forming Regions ◽  
Disk Star ◽  
Dust Mass ◽  
The Galaxy ◽  
Galaxy Disk

AbstractGalaxies with polar rings consist of two subsystems, a disk and a ring, which rotate almost in orthogonal planes. In this paper, we analyze the parameters characterizing the composition of the interstellar medium and star formation in star-forming complexes belonging to polar ring galaxy NGC660. We show that star-forming regions in the ring of the galaxy are distinctly different from those in the galaxy disk. They possess substantially lower infrared luminosities, which is indicative of less dust mass in these regions than in a typical disk star-forming region. UV and Hα luminosities also appear to be lower in the ring, which is likely a consequence of its relatively recent formation.

scholarly journals Spatially resolving the dust properties and submillimetre excess in M 33

2018 ◽  
Vol 613 ◽  
pp. A43 ◽  
Author(s):  
M. Relaño ◽  
I. De Looze ◽  
R. C. Kennicutt ◽  
U. Lisenfeld ◽  
A. Dariush ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Physical Properties ◽  
Relative Abundance ◽  
Radial Dependence ◽  
Dust Grains ◽  
Star Forming ◽  
Star Forming Regions ◽  
Dust Mass ◽  
The Galaxy ◽  
Dust Grain

Context. The relative abundance of the dust grain types in the interstellar medium is directly linked to physical quantities that trace the evolution of galaxies. Because of the poor spatial resolution of the infrared and submillimetre data, we are able to study the dependence of the resolved infrared spectral energy distribution (SED) across regions of the interstellar medium (ISM) with different physical properties in just a few objects. Aims. We aim to study the dust properties of the whole disc of M 33 at spatial scales of ~170 pc. This analysis allows us to infer how the relative dust grain abundance changes with the conditions of the ISM, study the existence of a submillimetre excess and look for trends of the gas-to-dust mass ratio (GDR) with other physical properties of the galaxy. Methods. For each pixel in the disc of M 33 we have fitted the infrared SED using a physically motivated dust model that assumes an emissivity index β close to two. We applied a Bayesian statistical method to fit the individual SEDs and derived the best output values from the study of the probability density function of each parameter. We derived the relative amount of the different dust grains in the model, the total dust mass, and the strength of the interstellar radiation field (ISRF) heating the dust at each spatial location. Results. The relative abundance of very small grains tends to increase, and for big grains to decrease, at high values of Hα luminosity. This shows that the dust grains are modified inside the star-forming regions, in agreement with a theoretical framework of dust evolution under different physical conditions. The radial dependence of the GDR is consistent with the shallow metallicity gradient observed in this galaxy. The strength of the ISRF derived in our model correlates with the star formation rate in the galaxy in a pixel by pixel basis. Although this is expected, it is the first time that a correlation between the two quantities has been reported. We have produced a map of submillimetre excess in the 500 μm SPIRE band for the disc of M 33. The excess can be as high as 50% and increases at large galactocentric distances. We further studied the relation of the excess with other physical properties of the galaxy and find that the excess is prominent in zones of diffuse ISM outside the main star-forming regions, where the molecular gas and dust surface density are low.

scholarly journals Inner and outer star forming regions over the disks of spiral galaxies

2019 ◽  
Vol 631 ◽  
pp. A23 ◽  
Author(s):  
M. Rodríguez-Baras ◽  
A. I. Díaz ◽  
F. F. Rosales-Ortega
Keyword(s):  
Star Formation ◽  
Physical Properties ◽  
Stochastic Effects ◽  
Oxygen Abundance ◽  
Star Forming ◽  
Star Forming Regions ◽  
Two Samples ◽  
The Galaxy ◽  
Galaxy Disk ◽  
Population Effects

Context. The H II regions are all studied employing the same general prescriptions and models, independently of the regions location in the galaxy disk. However, observed discrepancies between physical properties of inner and outer regions may indicate systematic differences in their star formation processes due to the influence of their environments. Aims. Through the analysis of inner and outer H II region observed spectra, we aim to explore possible systematic differences between the physical properties (metallicity, mass, and age) of their ionising clusters in order to study how star formation proceeds in different environments. Methods. We analysed two samples of 725 inner and 671 outer regions, characterised in the first paper of this series. Their functional parameters (oxygen abundances, ionisation parameters, and effective temperatures) were estimated and this parameter grid is employed as input for the computation of 540 Cloudy photoionisation models. Observed regions are compared with model predictions using diagnostic and evolutionary diagrams. Results. Higher metallicities are confirmed for the inner regions, although there are important discrepancies between the diagnostic diagrams. Calibrations based on the N2 index may underestimate inner regions oxygen abundances due to the [N II] saturation at solar metallicities. The degeneracy between the age and ionisation parameter affects oxygen abundance calibrations based on the O3N2 index. Innermost regions seem to have enhanced N/O ratios with respect to the expected values considering secondary production of nitrogen, which indicate an increase in the slope of the relation between N/O and O/H. Ionisation parameter calibrations based on the [S II]/Hα ratio are not valid for inner regions due to the observed bivalued behaviour of this ratio with O/H. Innermost regions have lower [O II]/[O III] ratio values than expected, indicating a possible non-linear relation between u and Z. Composite stellar populations (ionising and non-ionising) are present in both inner and outer regions, with an ionising contribution of around 1%. In considering the effects of evolution and underlying populations, inner regions show larger ionising cluster masses that possibly compose star-forming complexes. The most conservative lower limit for ionising cluster masses of outer regions indicate that they might be affected by stochastic effects. Equivalent widths indicate younger ages for outer regions, but degeneracy between evolution and underlying population effects prevent a quantitative determination. Nebular properties of the H II regions are also derived: inner regions have larger angular sizes, lower filling factors, and larger ionised hydrogen masses. Conclusions. Systematic physical differences are confirmed between ionising clusters of inner and outer H II regions. These differences condition the validity and range of reliability of oxygen abundance and ionisation parameter calibrations commonly applied to the study of H II regions.

scholarly journals Dissecting star formation in the “Atoms-for-Peace” galaxy

2018 ◽  
Vol 614 ◽  
pp. A130 ◽  
Author(s):  
K. George ◽  
P Joseph ◽  
P. Côté ◽  
S. K. Ghosh ◽  
J. B. Hutchings ◽  
...  
Keyword(s):  
Star Formation ◽  
Dwarf Galaxies ◽  
Initial Conditions ◽  
Dwarf Galaxy ◽  
Main Body ◽  
Star Forming ◽  
Uv Imaging ◽  
Star Forming Regions ◽  
The Galaxy ◽  
Tidal Tails

Context. The tidal tails of post-merger galaxies exhibit ongoing star formation far from their disks. The study of such systems can be useful for our understanding of gas condensation in diverse environments. Aims. The ongoing star formation in the tidal tails of post-merger galaxies can be directly studied from ultraviolet (UV) imaging observations. Methods. The post merger galaxy NGC7252 (“Atoms-for-Peace” galaxy) is observed with the Astrosat UV imaging telescope (UVIT) in broadband NUV and FUV filters to isolate the star-forming regions in the tidal tails and study the spatial variation in star formation rates. Results. Based on ultraviolet imaging observations, we discuss star-forming regions of ages <200 Myr in the tidal tails. We measure star formation rates in these regions and in the main body of the galaxy. The integrated star formation rate (SFR) of NGC7252 (i.e., that in the galaxy and tidal tails combined) without correcting for extinction is found to be 0.81 ± 0.01 M⊙ yr−1. We show that the integrated SFR can change by an order of magnitude if the extinction correction used in SFR derived from other proxies are taken into consideration. The star formation rates in the associated tidal dwarf galaxies (NGC7252E, SFR = 0.02 M⊙ yr−1 and NGC7252NW, SFR = 0.03 M⊙ yr−1) are typical of dwarf galaxies in the local Universe. The spatial resolution of the UV images reveals a gradient in star formation within the tidal dwarf galaxy. The star formation rates show a dependence on the distance from the centre of the galaxy. This can be due to the different initial conditions responsible for the triggering of star formation in the gas reservoir that was expelled during the recent merger in NGC7252.

scholarly journals Star Formation in Tadpole Galaxies

2014 ◽  
Vol 1 (1) ◽  
pp. 96-102 ◽  
Author(s):  
Casiana Muñoz-Tuñon ◽  
Jorge Sanchez Almeida ◽  
Debra M. Elmegreen ◽  
Bruce G. Elmegreen
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
High Redshift ◽  
Star Forming ◽  
Spatially Resolved ◽  
Test Models ◽  
The Galaxy ◽  
Galaxy Disk ◽  
Tail Structure ◽  
Remarkable Result

Tadpole Galaxies look like a star forming head with a tail structure to the side. They are also named cometaries. In a series of recent works we have discovered a number of issues that lead us to consider them extremely interesting targets. First, from images, they are disks with a lopsided starburst. This result is rmly  established with long slit spectroscopy in a nearby representative sample. They rotate with the head following the rotation pattern but displaced from the rotation center. Moreover, in a search for extremely metal poor (XMP) galaxies, we identied tadpoles as the dominant shapes in the sample - nearly 80% of the local XMP galaxies have a tadpole morphology. In addition, the spatially resolved analysis of the metallicity shows the remarkable result that there is a metallicity drop right at the position of the head. This is contrary to what intuition would say and dicult to explain if star formation has happened from gas processed in the disk. The result could however be understood if the star formation is driven by pristine gas falling into the galaxy disk. If conrmed, we could be unveiling, for the rst time, cool  ows in action in our nearby world. The tadpole class is relatively frequent at high redshift - 10% of resolvable galaxies in the Hubble UDF but less than 1% in the local Universe. They are systems that could track cool ows and test models of galaxy formation.

scholarly journals Star formation in Taurus Auriga Perseus and California nebulae

2015 ◽  
Vol 11 (S315) ◽  
Author(s):  
L. Viktor Tóth ◽  
Sarolta Zahorecz ◽  
Gabor Marton ◽  
Yasuo Doi ◽  
Toshikazu Onishi ◽  
...  
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Point Sources ◽  
Photometric Data ◽  
Stellar Object ◽  
Nearby Star ◽  
Young Stellar Object ◽  
Star Forming ◽  
Star Forming Regions ◽  
Ism Structure

AbstractStar formation and interstellar medium (ISM) structure were investigated in the Taurus, Auriga, Perseus and California (TAP) nearby star forming regions. Properties of the cold ISM was derived using AKARI FIR all sky maps, the Osaka-1.85m CO survey focusing to the all-sky Planck catalogue of Galactic Cold Clumps (PGCC). As many as 1041 infrared point sources were classified as young stellar object (YSO) based on multiband photometric data, and 384 of those are associated to a PGCC object. About 30% of the TAP PGCC clumps have associated YSOs.

scholarly journals Inner and outer star forming regions over the discs of spiral galaxies I. Sample characterization

2016 ◽  
Vol 11 (S321) ◽  
pp. 296-296
Author(s):  
Marina Rodríguez-Baras ◽  
A.I. Díaz ◽  
F.F. Rosales-Ortega
Keyword(s):  
Star Formation ◽  
Disk Galaxies ◽  
Work Sample ◽  
Star Forming ◽  
Star Forming Regions ◽  
Integral Field Spectroscopy ◽  
The Galaxy ◽  
Sample Characterization ◽  
Integral Field

AbstractThis project is aimed at understanding the dependence of star formation on the environment by analysing young stellar populations in two very different positions in disk galaxies: circumnuclear and outer disk giant regions. Integral field spectroscopy (IFS) provide an ideal means to achieve these goals providing simultaneous spatial and spectral resolution. Here we present the characterization of the work sample, composed by 671 outer regions and 725 inner regions from 263 isolated spirals galaxies observed by the CALIFA survey. The wide number of regions in both samples allows us to obtain statistically relevant results about the influence of metallicity, density and environment on star formation, and how it disseminates over the galaxy, to obtain evolutionary stories for the star-forming regions and to compare our results with models of massive star formation and galactic chemical evolution.

scholarly journals Survival of molecular gas in a stellar feedback-driven outflow witnessed with the MUSE TIMER project and ALMA

2019 ◽  
Vol 488 (3) ◽  
pp. 3904-3928 ◽  
Author(s):  
Ryan Leaman ◽  
Francesca Fragkoudi ◽  
Miguel Querejeta ◽  
Gigi Y C Leung ◽  
Dimitri A Gadotti ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Star Formation ◽  
Mechanical Energy ◽  
Molecular Gas ◽  
Ionized Gas ◽  
Star Forming ◽  
Stellar Feedback ◽  
Dominant Component ◽  
The Galaxy ◽  
Field Lines

ABSTRACT Stellar feedback plays a significant role in modulating star formation, redistributing metals, and shaping the baryonic and dark structure of galaxies – however, the efficiency of its energy deposition to the interstellar medium is challenging to constrain observationally. Here we leverage HST and ALMA imaging of a molecular gas and dust shell ($M_{\mathrm{ H}_2} \sim 2\times 10^{5}\, {\rm M}_{\odot }$) in an outflow from the nuclear star-forming ring of the galaxy NGC 3351, to serve as a boundary condition for a dynamical and energetic analysis of the outflowing ionized gas seen in our MUSE TIMER survey. We use starburst99 models and prescriptions for feedback from simulations to demonstrate that the observed star formation energetics can reproduce the ionized and molecular gas dynamics – provided a dominant component of the momentum injection comes from direct photon pressure from young stars, on top of supernovae, photoionization heating, and stellar winds. The mechanical energy budget from these sources is comparable to low luminosity active galactic neuclei, suggesting that stellar feedback can be a relevant driver of bulk gas motions in galaxy centres – although here ≲10−3 of the ionized gas mass is escaping the galaxy. We test several scenarios for the survival/formation of the cold gas in the outflow, including in situ condensation and cooling. Interestingly, the geometry of the molecular gas shell, observed magnetic field strengths and emission line diagnostics are consistent with a scenario where magnetic field lines aided survival of the dusty ISM as it was initially launched (with mass-loading factor ≲1) from the ring by stellar feedback. This system’s unique feedback-driven morphology can hopefully serve as a useful litmus test for feedback prescriptions in magnetohydrodynamical galaxy simulations.

scholarly journals Astrophysical MHD turbulence: confluence of observations, simulations, and theory

2012 ◽  
Vol 8 (S294) ◽  
pp. 325-336 ◽  
Author(s):  
Blakesley Burkhart ◽  
Alex Lazarian
Keyword(s):  
Star Formation ◽  
Interstellar Medium ◽  
Magnetic Reconnection ◽  
Particle Transport ◽  
Recent Progress ◽  
Critical Component ◽  
Dynamo Theory ◽  
Mhd Turbulence ◽  
The Galaxy

AbstractMagnetohydrodynamic (MHD) turbulence is a critical component of the current paradigms of star formation, dynamo theory, particle transport, magnetic reconnection and evolution of the ISM. In order to gain understanding of how MHD turbulence regulates processes in the Galaxy, a confluence of numerics, observations and theory must be imployed. In these proceedings we review recent progress that has been made on the connections between theoretical, numerical, and observational understanding of MHD turbulence as it applies to both the neutral and ionized interstellar medium.

scholarly journals Planck’s dusty GEMS

2018 ◽  
Vol 620 ◽  
pp. A60 ◽  
Author(s):  
R. Cañameras ◽  
N. P. H. Nesvadba ◽  
M. Limousin ◽  
H. Dole ◽  
R. Kneissl ◽  
...  
Keyword(s):  
Star Formation ◽  
Near Infrared ◽  
Infrared Imaging ◽  
High Redshift ◽  
Dust Emission ◽  
Galaxy Cluster ◽  
Star Forming ◽  
The Galaxy ◽  
Mass Outflow ◽  
Gas Accretion

We report the discovery of a molecular wind signature from a massive intensely star-forming clump of a few 109 M⊙, in the strongly gravitationally lensed submillimeter galaxy “the Emerald” (PLCK_G165.7+49.0) at z = 2.236. The Emerald is amongst the brightest high-redshift galaxies on the submillimeter sky, and was initially discovered with the Planck satellite. The system contains two magnificient structures with projected lengths of 28.5″ and 21″ formed by multiple, near-infrared arcs, falling behind a massive galaxy cluster at z = 0.35, as well as an adjacent filament that has so far escaped discovery in other wavebands. We used HST/WFC3 and CFHT optical and near-infrared imaging together with IRAM and SMA interferometry of the CO(4–3) line and 850 μm dust emission to characterize the foreground lensing mass distribution, construct a lens model with LENSTOOL, and calculate gravitational magnification factors between 20 and 50 in most of the source. The majority of the star formation takes place within two massive star-forming clumps which are marginally gravitationally bound and embedded in a 9 × 1010 M⊙, fragmented disk with 20% gas fraction. The stellar continuum morphology is much smoother and also well resolved perpendicular to the magnification axis. One of the clumps shows a pronounced blue wing in the CO(4–3) line profile, which we interpret as a wind signature. The mass outflow rates are high enough for us to suspect that the clump might become unbound within a few tens of Myr, unless the outflowing gas can be replenished by gas accretion from the surrounding disk. The velocity offset of –200 km s−1 is above the escape velocity of the clump, but not that of the galaxy overall, suggesting that much of this material might ultimately rain back onto the galaxy and contribute to fueling subsequent star formation.

scholarly journals The Violent Interstellar Medium of Nearby Dwarf Galaxies

1999 ◽  
Vol 16 (1) ◽  
pp. 106-112 ◽  
Author(s):  
Fabian Walter
Keyword(s):  
Interstellar Medium ◽  
Gamma Ray ◽  
Dwarf Galaxies ◽  
Young Star ◽  
Stellar Winds ◽  
Star Forming ◽  
Star Forming Regions ◽  
Supernova Explosions ◽  
High Velocity Clouds ◽  
Ob Associations

AbstractHigh resolution HI observations of nearby dwarf galaxies (most of which are situated in the M81 group at a distance of about 3·2 Mpc) reveal that their neutral interstellar medium (ISM) is dominated by hole-like features most of which are expanding. A comparison of the physical properties of these holes with the ones found in more massive spiral galaxies (such as M31 and M33) shows that they tend to reach much larger sizes in dwarf galaxies. This can be understood in terms of the galaxy's gravitational potential. The origin of these features is still a matter of debate. In general, young star forming regions (OB-associations) are held responsible for their formation. This picture, however, is not without its critics and other mechanisms such as the infall of high velocity clouds, turbulent motions or even gamma ray bursters have been recently proposed. Here I will present one example of a supergiant shell in IC 2574 which corroborates the picture that OB associations are indeed creating these structures. This particular supergiant shell is currently the most promising case to study the effects of the combined effects of stellar winds and supernova explosions which shape the neutral interstellar medium of (dwarf) galaxies.

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