scholarly journals Stellar Populations of a Sample of Tidal Dwarf Galaxies

2004 ◽  
Vol 217 ◽  
pp. 540-545 ◽  
Author(s):  
Peter M. Weilbacher ◽  
Uta Fritze-V. Alvensleben ◽  
Pierre-Alain Duc
Keyword(s):  
Formation Mechanism ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Velocity Structure ◽  
Dwarf Galaxies ◽  
Stellar Populations ◽  
Evolutionary Synthesis ◽  
Optical Images ◽  
Stellar Masses ◽  
Parent Galaxy

We investigate the stellar populations of a sample of Tidal Dwarf Galaxies, combining observations and evolutionary synthesis models to try and reveal their formation mechanism. on optical images we select a first sample of TDGs for which optical spectroscopy is used to measure metallicities and velocity structure. Finally, we estimate ages, burst strengths, and stellar masses from near-infrared imaging in comparison with a dedicated grid of evolutionary synthesis models, to assess if Tidal Dwarfs are formed out of collapsing gas clouds or by an accumulation of old stars from the parent galaxy or by a combination of both.

The Nature of Boxy/Peanut Spiral Galaxies: Overview and New Results

1997 ◽  
Vol 14 (2) ◽  
pp. 146-158 ◽  
Author(s):  
M. Bureau ◽  
K. C. Freeman
Keyword(s):  
Formation Mechanism ◽  
Vertical Structure ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Spiral Galaxies ◽  
Physical Conditions ◽  
Bar Buckling ◽  
Line Imaging ◽  
Observational Program

AbstractThe formation mechanism of boxy/peanut-shaped bulges in spiral galaxies has been a problem for many years. We briefly review here the possible formation scenarios for boxy/peanut bulges, concentrating on both the bar-buckling and accretion hypotheses, and then describe an observational program aimed at testing those various theories and studying the vertical structure of edge-on bars. Our program includes optical long-slit spectroscopy, Hiline-imaging, near-infrared imaging, and multi-band optical imaging. New spectroscopic results (both optical and Hi) are presented on seven galaxies, including five boxy/peanut-bulge spirals. Based on Kuijken & Merrifield's (1995) idea for detecting edge-on bars, we argue that these observations constitute a strong case in favour of the bar-buckling mechanism for the formation of boxy/peanut-shaped bulges, but they also raise many questions and prompt for more detailed modelling to be made. The implications of the observations concerning the determination of rotation curves and of the physical conditions in bulges are also discussed.

scholarly journals Extragalactic GCs in the near-infrared: genuinely old in E/S0's?

2009 ◽  
Vol 5 (S262) ◽  
pp. 315-316
Author(s):  
Ana L. Chies-Santos ◽  
Søren S. Larsen
Keyword(s):  
Globular Cluster ◽  
Stellar Population ◽  
Near Infrared ◽  
Local Group ◽  
Stellar Populations ◽  
Age Dating ◽  
Early Type ◽  
Optical Photometry ◽  
Star Forming ◽  
Optical Images

Globular cluster (GC) systems are powerful probes to study the evolutionary histories of galaxies, being tracers of major star fomation episodes (Brodie & Strader 2006). They are found around all major galaxies and are easy to see far beyond the local group. Age dating GCs therefore helps pinpoint epochs of major star forming events. Spectroscopic age dating though (Strader et al. 2005) is extremely time consuming and can only access the few brightest clusters. An alternative is to combine near-infrared (NIR) and optical photometry, and therefore have a better chance in lifting the age metallicity degeneracy than with optical colours alone. This approach relies in testing GC colours against simple stellar population (SSP) models. The first studies following this technique showed the possible existence of a high percentage of intermediate age (2-3 Gyrs) GCs in early-type galaxies known to contain old stellar populations from integrated light studies. Two strong cases can be listed: NGC 4365 (Puzia et al. 2002, Larsen et al. 2005) and NGC 5846 (Hempel et al. 2003). In the present study we combine NIR deep photometry obtained with the WHT/LIRIS instrument and archival HST/ACS optical images to determine g(F475W), z(F840LP) and K(2.2m) magnitudes and colours of GCs in 14 early-type galaxies.

scholarly journals Galaxy build-up at cosmic dawn: Insights from deep observations with Hubble, Spitzer, and ALMA

2019 ◽  
Vol 15 (S352) ◽  
pp. 12-12
Author(s):  
Pascal Oesch
Keyword(s):  
Rest Frame ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Hubble Space Telescope ◽  
Uv Light ◽  
Big Bang ◽  
Limited Information ◽  
Imaging Data ◽  
Early Galaxies ◽  
Stellar Masses

AbstractOver the last few years, great progress has been made in understanding the build-up of the first generations of galaxies based on deep optical and near-infrared imaging from the Hubble Space Telescope. However, HST only samples the rest-frame UV light of galaxies at z …4, providing only limited information on the dust obscuration and on stellar masses of these sources. Fortunately, several Spitzer/IRAC programs have complemented the extragalactic HST fields with ultra-deep imaging data, allowing for a rest-frame optical view on early galaxies. Together with first ALMA/ NOEMA (sub)mm observations on distant galaxies, we are starting to gain a more and more complete picture of galaxy star-formation and mass build-up in the early universe. In this talk, I will present an overview of our current understanding of normal star-forming galaxies at z > 3 based the combination of HST+Spitzer+ALMA/NOEMA data. In particular, I will show how HST as already pushed into JWST territory with the discovery and spectroscopic confirmation of a galaxy at z = 11.1 ± 0.1, only : 400 Myr after the Big Bang. I will also highlight some of the exciting possibilities that lie ahead with JWST to push the spectroscopic frontier to the cosmic dawn and to finally probe the physics of early galaxies.

scholarly journals A near-infrared view of AGB stars in nearby dwarf galaxies

2009 ◽  
Vol 5 (S262) ◽  
pp. 345-346
Author(s):  
M. Gullieuszik ◽  
E. V. Held ◽  
L. Girardi ◽  
L. Rizzi ◽  
P. Marigo ◽  
...  
Keyword(s):  
Near Infrared ◽  
Dwarf Galaxies ◽  
Theoretical Models ◽  
Stellar Populations ◽  
Agb Stars ◽  
Dwarf Spheroidal Galaxies ◽  
Luminosity Functions ◽  
Spheroidal Galaxies

AbstractAs part of our near-infrared photometric survey of nearby dwarf galaxies, we present recent results for Leo I and Leo II dwarf spheroidal galaxies. We selected O- and C-rich AGB stellar populations using two-color diagrams and compared their luminosity functions and star counts with the predictions of the most recent AGB theoretical models.

scholarly journals SUBARU near-infrared multi-color images of Class II Young Stellar Object, RNO91

2006 ◽  
Vol 2 (S237) ◽  
pp. 447-447
Author(s):  
Satoshi Mayama ◽  
Motohide Tamura ◽  
Masahiko Hayashi
Keyword(s):  
Near Infrared ◽  
Infrared Imaging ◽  
Infrared Camera ◽  
Central Peak ◽  
Class Ii ◽  
Peak Position ◽  
Infrared Light ◽  
Molecular Outflows ◽  
The North ◽  
Optical Images

AbstractRNO91 is class II source currently in a transition phase between a protostar and a main-sequence star. It is known as a source of complex molecular outflows. Previous studies suggested that RNO91 was associated with a reflection nebula, a CO outflow, shock-excited H2 emission, and disk type structure. But the geometry of RNO91, especially its inner region, is not well confirmed yet. High resolution imaging is needed to understand the nature of RNO91 and its interaction with outflow. Thus, we conducted near-infrared imaging observations of RNO91 with the infrared camera CIAO mounted on the Subaru 8.2-m Telescope. We presented JHK band and optical images which resolved a complex asymmetrical circumstellar structure. We examined the color of RNO91 nebula and compared the geometry of the system suggested by our data with that already proposed on the basis of other studies. Our main results are as follows; 1. The K-band images show significant halo emission detected within ~2″ around the peak position while less halo emission is seen in shorter wavelength images such as J and optical. The nebula appears to become more circular and more diffuse with increasing wavelengths. The cut-off at 300AU derived from our radial surface brightness is consistent with the size of the polarization disk suggested by Draper & Tadhunter (1993). These consistencies indicate that this optically thick region is attributed to a disk-like structure.2. At J and optical, several bluer knot-like structures are detected around and beyond the halo emission. These bluer knots seen in our images are comparable to the size of the envelope detected in HCO+ emission surrounding RNO91 (Lee & Ho 2005). It is thus natural to suggest that these bluer knots are the near-infrared light scattered by an envelope structure which is disrupted by molecular outflows.3. The pseudo-true color composite image has an appearance of arc-shaped emission extending to the north and to the east through RNO91. On the counter part of this arc-shaped structure, the nebula appears to become more extended to the southwest from the central peak position in J band and optical images. We interpret these whole structures as a bottom of bipolar cavity seen relatively edge-on opening to the north and south directions.

scholarly journals An ALMA survey of the S2CLS UDS field: optically invisible submillimetre galaxies

2021 ◽  
Vol 502 (3) ◽  
pp. 3426-3435
Author(s):  
Ian Smail ◽  
U Dudzevičiūtė ◽  
S M Stach ◽  
O Almaini ◽  
J E Birkin ◽  
...  
Keyword(s):  
Star Formation ◽  
Surface Density ◽  
Near Infrared ◽  
Infrared Imaging ◽  
High Redshift ◽  
Formation Rate ◽  
High Attenuation ◽  
Deep Survey ◽  
Stellar Masses ◽  
Dust Attenuation

ABSTRACT We analyse a robust sample of 30 near-infrared-faint (KAB > 25.3, 5σ) submillimetre galaxies (SMGs) selected from a 0.96 deg2 field to investigate their properties and the cause of their faintness in optical/near-infrared wavebands. Our analysis exploits precise identifications based on Atacama Large Millimeter Array (ALMA) 870-μm continuum imaging, combined with very deep near-infrared imaging from the UKIDSS Ultra Deep Survey. We estimate that SMGs with KAB > 25.3 mag represent 15 ± 2 per cent of the total population brighter than S870 = 3.6 mJy, with a potential surface density of ∼450 deg−2 above S870 ≥ 1 mJy. As such, they pose a source of contamination in surveys for both high-redshift ‘quiescent’ galaxies and very high redshift Lyman-break galaxies. We show that these K-faint SMGs represent the tail of the broader submillimetre population, with comparable dust and stellar masses to KAB ≤ 25.3 mag SMGs, but lying at significantly higher redshifts (z = 3.44 ± 0.06 versus z = 2.36 ± 0.11) and having higher dust attenuation (AV = 5.2 ± 0.3 versus AV = 2.9 ± 0.1). We investigate the origin of the strong dust attenuation and find indications that these K-faint galaxies have smaller dust continuum sizes than the KAB ≤ 25.3 mag galaxies, as measured by ALMA, which suggests their high attenuation is related to their compact sizes. We identify a correlation of dust attenuation with star formation rate surface density (ΣSFR), with the K-faint SMGs representing the higher ΣSFR and highest AV galaxies. The concentrated, intense star formation activity in these systems is likely to be associated with the formation of spheroids in compact galaxies at high redshifts, but as a result of their high obscuration these galaxies are completely missed in ultraviolet, optical, and even near-infrared surveys.

scholarly journals High resolution near-infrared imaging of submillimeter galaxies

2012 ◽  
Vol 8 (S295) ◽  
pp. 53-54
Author(s):  
Paula Aguirre ◽  
Andrew J. Baker ◽  
Felipe Menanteau ◽  
Dieter Lutz ◽  
Linda J. Tacconi
Keyword(s):  
High Resolution ◽  
Ir Spectroscopy ◽  
Rest Frame ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Near Infrared Imaging ◽  
Submillimeter Galaxies ◽  
Multiple Component ◽  
Stellar Masses

AbstractWe have obtained high-resolution F110W (~ J) and F160W (~ H) band observations of ten submillimeter galaxies (SMGs) with the Hubble Space Telescope's NICMOS camera, in order to resolve their rest-frame optical morphologies, determine the existence of multiple-component, merger-like configurations, and estimate their stellar masses. The selected targets have redshifts in the range 2.2≤ z ≤ 2.81 confirmed with millimeter or mid-IR spectroscopy, guaranteeing that the two bands sample the galaxies' rest-frame optical light with the Balmer break falling between them.

scholarly journals Very Low Mass Stellar Populations in Star-Forming Regions: Near-Infrared Luminosity Functions and Mass Functions

2003 ◽  
Vol 211 ◽  
pp. 91-96 ◽  
Author(s):  
Yumiko Oasa
Keyword(s):  
Near Infrared ◽  
Stellar Populations ◽  
Mass Function ◽  
High Mass ◽  
Star Forming ◽  
Star Forming Regions ◽  
Luminosity Functions ◽  
Low Mass ◽  
Stellar Masses ◽  
Mass Functions

We briefly describe recent studies of the low-mass young stellar populations including substellar objects and of their luminosity functions and mass functions, especially at lower-ends, in different star-forming regions. The mass function is determined by the technique based on the near-infrared photometry for estimating stellar luminosities and then translating them into stellar masses. We compare the local environmental characteristics of regions in which high-mass stars form with those of regions producing only low-mass stars and intermediate stars. We find that there exist numerous very low-mass YSO candidates including young brown dwarfs and young isolated objects with planetary masses in common. Further, the luminosity functions and mass functions in the star-forming regions might not have a uniform shape below the hydrogen-burning limit.

scholarly journals Ultra-faint Lyman Alpha Emitters with MUSE

2019 ◽  
Vol 15 (S352) ◽  
pp. 331-335
Author(s):  
Michael V. Maseda ◽  
Keyword(s):  
Near Infrared ◽  
Infrared Imaging ◽  
Hubble Space Telescope ◽  
Optical Emission ◽  
Star Forming ◽  
Very Large Telescope ◽  
Lyman Alpha Emitters ◽  
Integral Field Spectrograph ◽  
Hubble Ultra Deep Field ◽  
Stellar Masses

AbstractUsing an ultra-deep, untargeted survey with the MUSE integral field spectrograph on the ESO Very Large Telescope, we obtain spectroscopic redshifts to a depth never explored before: galaxies with observed magnitudes m > 30–32. Specifically, we detect objects via Lyman-α emission at 2.9 < z < 6.7 without individual continuum counterparts in areas covered by the deepest optical/near-infrared imaging taken by the Hubble Space Telescope, the Hubble Ultra Deep Field. In total, we find more than 100 such objects in 9 square arcminutes at these redshifts, also including a number of sources that are visible only in the HST band that contains Lyman-α. Detailed HST and IRAC stacking analyses confirm the Lyman-α emission as well as the 1216 Å breaks, faint UV continua (MUV ∼ −15), and optical emission lines: these objects are the faintest spectroscopically-confirmed galaxies at high-z. The blue UV continuum slopes and measurements/limits on the equivalent widths of Lyman-α, which in some cases exceeds 300 Å, are consistent with ages < 10 Myr, metallicities < 5% solar, and stellar masses < 107–8 solar masses. The nature of these types of objects is intriguing as they could be the faint star-forming sources of Reionization and could represent the initial (strong) phase of stellar mass growth in galaxies.

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