Young stellar clusters triggered by a density wave in NGC 2997

AbstractBright knots along the arms of grand-design spiral galaxies are frequently seen on near-infrared K-band images. To investigate their nature, low resolution K-band spectra of a string of knots in the southern arm of the grand design, spiral galaxy NGC 2997 were obtained with ISAAC/VLT. Most of the knots show strong Brγ emission while some have H2 and HeI emission. A few knots show indications of CO absorption. Their spectra and absolute K magnitudes exceeding -12 mag suggest them to be very compact, young stellar clusters with masses up to 5 × 104 M. The knots' azimuthal distance from the K-band spiral correlates well with their Brγ strength, indicating that they are located inside the co-rotation of the density wave, which triggered them through a large-scale, star-forming front. These relative azimuthal distances suggest an age spread of more than 1.6 Myr, which is incompatible with standard models for an instantaneous star burst. This indicates a more complex star-formation history, such as several bursts or continuous formation.

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Bright knots along spiral arms in disk galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307002049 ◽

2006 ◽

Vol 2 (S237) ◽

pp. 416-416

Author(s):

P. Grosbøl ◽

H. Dottori

Keyword(s):

High Resolution ◽

Large Scale ◽

Spiral Galaxies ◽

Density Wave ◽

Disk Galaxies ◽

Stellar Clusters ◽

Spiral Arms ◽

K Band

AbstractMany spiral galaxies show bright knots along their arms on high resolution K-band images. Spectroscopy of such knots suggests that they are very young stellar clusters which formation was triggered by a large-scale front associated to a density wave. We have studied a sample of around 80 disk galaxies (with i < 65°) for which deep K-band maps with a resolution of <1″ are available and present preliminary statistics of such bright knots.

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Principal component analysis tomography in near-infrared integral field spectroscopy of young stellar objects – I. Revisiting the high-mass protostar W33A

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab358 ◽

2021 ◽

Vol 503 (1) ◽

pp. 270-291

Author(s):

F Navarete ◽

A Damineli ◽

J E Steiner ◽

R D Blum

Keyword(s):

Large Scale ◽

Near Infrared ◽

Rotation Axis ◽

Principal Component ◽

Young Stellar Objects ◽

High Mass ◽

Continuum Emission ◽

Rotating Disc ◽

Stellar Objects ◽

K Band

ABSTRACT W33A is a well-known example of a high-mass young stellar object showing evidence of a circumstellar disc. We revisited the K-band NIFS/Gemini North observations of the W33A protostar using principal components analysis tomography and additional post-processing routines. Our results indicate the presence of a compact rotating disc based on the kinematics of the CO absorption features. The position–velocity diagram shows that the disc exhibits a rotation curve with velocities that rapidly decrease for radii larger than 0.1 arcsec (∼250 au) from the central source, suggesting a structure about four times more compact than previously reported. We derived a dynamical mass of 10.0$^{+4.1}_{-2.2}$ $\rm {M}_\odot$ for the ‘disc + protostar’ system, about ∼33 per cent smaller than previously reported, but still compatible with high-mass protostar status. A relatively compact H2 wind was identified at the base of the large-scale outflow of W33A, with a mean visual extinction of ∼63 mag. By taking advantage of supplementary near-infrared maps, we identified at least two other point-like objects driving extended structures in the vicinity of W33A, suggesting that multiple active protostars are located within the cloud. The closest object (Source B) was also identified in the NIFS field of view as a faint point-like object at a projected distance of ∼7000 au from W33A, powering extended K-band continuum emission detected in the same field. Another source (Source C) is driving a bipolar $\rm {H}_2$ jet aligned perpendicular to the rotation axis of W33A.

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Recent Star Formation History of the Magellanic Clouds

Symposium - International Astronomical Union ◽

10.1017/s0074180900118649 ◽

1999 ◽

Vol 190 ◽

pp. 470-472

Author(s):

Eva K. Grebel ◽

Wolfgang Brandner

Keyword(s):

Star Formation ◽

Large Scale ◽

New Age ◽

Magellanic Clouds ◽

Star Formation History ◽

Star Forming ◽

Formation History ◽

History Of

A new age calibration of Cepheids and supergiants is used to study the large-scale recent star formation history of the LMC and the SMC. We find evidence for migration of star formation along the LMC bar as well as for the existence of long-lived (≈ 200 Myr) extended star-forming features.

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Dynamics of the Gas in Spiral Galaxies

International Astronomical Union Colloquium ◽

10.1017/s0252921100067312 ◽

1977 ◽

Vol 45 ◽

pp. 11-30 ◽

Cited By ~ 1

Author(s):

William W. Roberts

Keyword(s):

Observational Studies ◽

Large Scale ◽

Density Wave ◽

Wave Theory ◽

Relative Distribution ◽

Star Forming ◽

Molecule Formation ◽

Gaseous Component ◽

Density Wave Theory ◽

Co Observations

AbstractThe dynamics of the gaseous component in disk-shaped galaxies is thought to play an important governing role in star formation, molecule formation, and the degree of development of spiral structure. The prospect that density waves and galactic shock waves are present on the large-scale has received support in recent years from a variety of observational studies. Large-scale shocks provide a most promising mechanism for driving star-forming and molecule-forming events on the scales of many kpc along spiral arms. Such shocks may also govern the kinematics and relative distribution of various galactic tracers. This is particularly apparent in M81 and other external spirals, because of our “bird’s-eye-view” perspective, and for the tracers of HI and CO in our own Galaxy. Comparison of the CO observations with model simulations based on the precepts of the density wave theory shows that these precepts are supported by several observational results.

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Comparing ALMA, VLT, and HST data for Massive, Young Clusters in Grand-Design Spirals

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316007080 ◽

2015 ◽

Vol 12 (S316) ◽

pp. 141-142

Author(s):

Preben Grosbøl ◽

Horacio Dottori

Keyword(s):

Near Infrared ◽

Detailed Comparison ◽

Stellar Clusters ◽

Giant Molecular Clouds ◽

Cluster Complexes ◽

Stellar Cluster ◽

Grand Design ◽

Nearby Galaxies ◽

Massive Clusters ◽

Co Emission

AbstractA population of young, massive stellar cluster complexes with near-infrared (NIR) colors indicating high extinction (i.e. Av ~ 7m) was identified on HAWK-I/VLT images of several nearby, grand-design spiral galaxies. Models suggest that they are very young cluster complexes still embedded in a dust/gas envelope which will be expelled after 5-7 Myr. This type of very young, embedded clusters are not seen in optical studies using HST data.A detailed comparison of HST and HAWK-I images was done to better understand the discrepancy between the optical and NIR detection of stellar clusters in nearby galaxies. More than 70% of the NIR clusters are located close to dust lanes which would make an optical detection difficult. A comparison of the ALMA CO(1-0)-map of NGC 4321 and the young, massive clusters shows that 60% of them have CO emission within 2“ indicating a correlation between giant molecular clouds and formation of massive clusters.

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STAR-FORMING REGION Sh 2-233IR. I. DEEP NEAR-INFRARED OBSERVATIONS TOWARD THE EMBEDDED STELLAR CLUSTERS

The Astrophysical Journal ◽

10.1088/0004-637x/720/1/1 ◽

2010 ◽

Vol 720 (1) ◽

pp. 1-8 ◽

Cited By ~ 5

Author(s):

Chi-Hung Yan ◽

Y. C. Minh ◽

Shiang-Yu Wang ◽

Yu-Nang Su ◽

Adam Ginsburg

Keyword(s):

Near Infrared ◽

Stellar Clusters ◽

Infrared Observations ◽

Star Forming

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The Nuclear Ring in the Barred Spiral Galaxy IC 4933

Publications of the Astronomical Society of Australia ◽

10.1071/as09016 ◽

2010 ◽

Vol 27 (1) ◽

pp. 56-63 ◽

Cited By ~ 5

Author(s):

Stuart D. Ryder ◽

Samuel M. Illingworth ◽

Robert G. Sharp ◽

Catherine L. Farage

Keyword(s):

Spiral Galaxy ◽

Near Infrared ◽

Infrared Imaging ◽

Star Formation History ◽

Star Forming ◽

Star Forming Regions ◽

The North ◽

Contact Points ◽

Nuclear Ring ◽

Barred Spiral Galaxy

AbstractWe present infrared imaging from IRIS2 on the Anglo–Australian Telescope that shows the barred spiral galaxy IC 4933 has not just an inner ring encircling the bar, but also a star-forming nuclear ring 1.5 kpc in diameter. Imaging in the u′ band with GMOS on Gemini South confirms that this ring is not purely an artifact due to dust. Optical and near-infrared colours alone however cannot break the degeneracy between age, extinction, and burst duration that would allow the star formation history of the ring to be unraveled. Integral field spectroscopy with the GNIRS spectrograph on Gemini South shows the equivalent width of the Paβ line to peak in the north and south quadrants of the ring, indicative of a bipolar azimuthal age gradient around the ring. The youngest star-forming regions do not appear to correspond to where we expect to find the contact points between the offset dust lanes and the nuclear ring unless the nuclear ring is oval in shape, causing the contact points to lead the bar by more than 90°.

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FIGS: spectral fitting constraints on the star formation history of massive galaxies since the cosmic noon

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz849 ◽

2019 ◽

Vol 486 (1) ◽

pp. 1358-1376 ◽

Cited By ~ 3

Author(s):

Ignacio Ferreras ◽

Anna Pasquali ◽

Nor Pirzkal ◽

John Pharo ◽

Sangeeta Malhotra ◽

...

Keyword(s):

Star Formation ◽

Near Infrared ◽

Age Distribution ◽

Principal Component ◽

Stellar Mass ◽

Star Formation History ◽

Population Parameters ◽

Massive Galaxies ◽

Star Forming ◽

Spectral Fitting

Abstract We constrain the stellar population properties of a sample of 52 massive galaxies – with stellar mass log (Ms/M⊙) ≳ 10.5 – over the redshift range 0.5 < z < 2 by use of observer-frame optical and near-infrared slitless spectra from Hubble Space Telescope’s ACS and WFC3 grisms. The deep exposures (∼100 ks) allow us to target individual spectra of massive galaxies to F160W = 22.5 AB. Our spectral fitting approach uses a set of six base models adapted to the redshift and spectral resolution of each observation, and fits the weights of the base models, including potential dust attenuation, via a Markov Chain Monte Carlo method. Our sample comprises a mixed distribution of quiescent (19) and star-forming galaxies (33). We quantify the width of the age distribution (Δt) that is found to dominate the variance of the retrieved parameters according to principal component analysis. The population parameters follow the expected trend towards older ages with increasing mass, and Δt appears to weakly anticorrelate with stellar mass, suggesting a more efficient star formation at the massive end. As expected, the redshift dependence of the relative stellar age (measured in units of the age of the Universe at the source) in the quiescent sample rejects the hypothesis of a single burst (aka monolithic collapse). Radial colour gradients within each galaxy are also explored, finding a wider scatter in the star-forming subsample, but no conclusive trend with respect to the population parameters.

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5.19. A high resolution CO map of the inner region of M51

Symposium - International Astronomical Union ◽

10.1017/s0074180900084813 ◽

1998 ◽

Vol 184 ◽

pp. 249-250

Author(s):

S. Aalto ◽

S. Hüttemeister ◽

N. Scoville ◽

P. Thaddeus

Keyword(s):

High Resolution ◽

Spiral Galaxy ◽

Density Wave ◽

Linear Size ◽

Structural Studies ◽

Spiral Density Wave ◽

Systemic Velocity ◽

Grand Design ◽

Inner Region ◽

Design Spiral

M51, the Whirlpool Galaxy, at a distance of ≈ 9,6 Mpc and a systemic velocity of 465 km s−1, is the closest “Grand Design” spiral galaxy. Its low inclination (20°) makes it an excellent target for structural studies, e.g. the formation of arms in response to a spiral density wave causing gas streaming motions. We have obtained a high resolution, sensitive map of the inner 2.5′ of M51 using the Caltech six-element OVRO array. The map consists of a 19-field mosaic, taken using three different telescope configurations. The resolution is 2.5″, (corresponding to 115 pc linear size) and 3.5” for the robustly and naturally weigthed maps, respectively.

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