Found 11 talks width keyword starburst galaxies
I will present a multiwavelength study of a large MIPS selected galaxies and satisfy a certain IRAC color criterion. Stellar population modeling and IRS spectra together demonstrate that the double criteria used to select this sample have efficiently isolated massive star-forming galaxies at /z/ ~ 1.9. This is the first starburst (SB)-dominated ultraluminous infrared galaxies (ULIRG) sample at high redshift with total infrared luminosity measured directly from Spitzer, Herschel FIR and millimeter photometry, and as such gives us the first accurate view of broadband spectral energy distributions for SB galaxies at extremely high luminosity and at all wavelengths. The HST images in optical and NIR bands show that most objects have very extended morphologies in the rest-frame ultraviolet and optical band, thus extended distribution of PAH molecules. We conclude that objects in this sample are ULIRGs powered mainly by SB; and the total infrared luminosity density contributed by this type of objects at /z/ ~ 1.9.
With the aim of testing the relation between supernova (SN) rate and star formation rate, we conducted a SN search in a sample of local starburst galaxies (SBs) where both star formation rates and extinction are extremely high. The search was performed in the near-infrared, where the bias due to extinction is reduced using HAWK-I on the VLT. We discovered six SNe, in excellent agreement with expectations, when considering that, even in our search, about 60% of events remain hidden in the nuclear regions due to a combination of reduced search efficiency and very high extinction.
In addition I will present my plans for next months at IAC for the "Starbursts and EMIR project". I will participate in the commissioning of the instrument at La Palma, collaborating in the development of the ETC and I will compile a catalog of starbursts for EMIR with the aim to study their imprint in the cosmic evolution of galaxies.
In order to understand galaxy formation it is crucial to obtain sensitive observations of the emission of dust and molecular gas both of which constrain the on-going star formation or AGN activity and the future potential of the galaxy to grow. Constraining the growth of ensemble of galaxies in the distant universe and not simply the most active ones, is one of the primary goals of current and planned (sub)mm facilities such as ALMA or SPICA. I will discuss two major questions in galaxy formation and assembly: 1) are dusty galaxies vigorously forming stars embedded within large scale structures at z>1.5; and 2) do dusty starbursts exist at the highest redshift. To shed light on these obscure topics, I will present our on-going observations of dust and molecular gas with a number of different (sub)mm facilities such as Herschel, APEX, IRAM or ALMA of one important star forming galaxy population in the distant universe: submillimeter selected galaxies (SMGs). My presentation will be complemented by our recently initiated census of the molecular gas reservoirs of nearby galaxies with optical IFU coverage. The local analogs serve as a reference sample for current and future studies of high-z galaxy populations.
AzTEC is a sensitive bolometer camera that, coupled with 10-15m-class sub-mm telescopes, has mapped more than 3 sq. deg of the extragalactic sky to depths between 0.7 and 1.1 mJy at 1.1mm, prior to its current installation and operation on the 32m Large Millimeter Telescope (LMT). These extragalactic surveys targeted towards blank-fields and biased high-z environments alike have allowed us to identify regions of the sky where submillimeter galaxies (SMGs), powerful obscured starbursts at high-redshifts (z>1), cluster, and possibly mark the potential wells of accelerated galaxy-formation that will eventually form massive clusters. In this talk I will describe the evidence we have found for these overdense regions of massive galaxies, their structure and possible interpretation, as well as the follow-up observations we are carrying out with the LMT nowadays.
How do the first galaxies form and evolve? Optical and near-infrared deep surveys are now finding galaxies at very high redshifts. However, they are typically small, not massive and present some but not very high star formation. But now the Herschel Multi-tiered Extragalactic Survey (HerMES), the largest project that has being carried out with the Herschel Space Observatory, in collaboration with other groups, has discovered a massive, maximum-starburst galaxy at a redshift of 6.34. The presence of galaxies like HFLS3 in the early Universe challenges current theories of galaxy fomation and evolution. I will describe the method we have developed to find these galaxies, the follow-up observations with different facilities and the main physical properties of this extreme object.
The fate of ionizing radiation from massive stars has fundamental consequences on scales ranging from the physics of circumstellar disks to the ionization state of the entire universe. On galactic scales, the radiative feedback from massive stars is a major driver for the energetics and phase balance of the interstellar medium in star-forming galaxies. While even starburst galaxies appear to be largely optically thick in the Lyman continuum, ionization-parameter mapping shows that significant populations of HII regions within galaxies are optically thin, powering the diffuse, warm ionized medium. I will discuss our multi-faceted work to clarify our understanding of radiative feedback in star-forming galaxies from the Magellanic Clouds to starbursts.
Over the past years observations of young and populous star clusters have shown that the stellar initial mass function (IMF) can be conveniently described by a two-part power-law with an exponent alpha2 = 2.3 for stars more massive than about 0.5 Msol and an exponent of alpha1 = 1.3 for less massive stars. A consensus has also emerged that most, if not all, stars form in stellar groups and star clusters, and that the mass function of these can be described as a power-law (the embedded cluster mass function, ECMF) with an exponent beta ~2. These two results imply that the integrated galactic IMF (IGIMF) for early-type stars cannot be a Salpeter power-law, but that they must have a steeper exponent. An application to star-burst galaxies shows that the IGIMF can become top-heavy. This has important consequences for the distribution of stellar remnants and for the chemo-dynamical and photometric evolution of galaxies.
AbstractIn this talk, I will cover our contribution to the study of extremely red galaxy (ERG) populations presenting a multi-wavelength analysis of these objects, selected in the GOODS-South/Chandra Deep Field South field. By using all the photometric (from X-rays to radio) and spectroscopic information available on large deep samples of extremely red objects (EROs, 645 sources), infrared EROs (IEROs, 294 sources) and distant red galaxies (DRGs, 350 sources), we derive redshift distributions, identify AGN powered and star-formation powered galaxies (based on X-ray properties and a new IR AGN diagnostic developed by us), and, using the radio observations of this field, estimate robust (AGN- and dust-unbiased) star formation rate densities (SFRD) for these populations. Applying a redshift separation (1 ≤ z < 2 and 2 ≤ z ≤ 3) we find a significant rise (a factor of 1.5 — 3) of SFRD for EROs and DRGs toward high-z, while none is observed for IEROs. As expected, we find a significant overlap between the ERG populations, and investigate the properties of "pure" (galaxies that conform to only one of the three considered ERG criteria) and "combined" (galaxies conforming to all three criteria) sub-populations. We find ERG sub-populations with no AGN activity and intense star-formation rates. With average values of ~180 M⊙/yr at 2 ≤ z < 3, they reasonably contribute to the global star-formation rate density, reaching a > 20% level. Strong AGN behaviour is not observed in the ERG population, with AGN only increasing the average radio luminosity of ERGs by 10 — 20%. However, AGN are frequently found (in up to 27% of the ERG population), and would increase the SFRD estimate by over 100%. Thus, and while the contribution of SF processes to the radio luminosity in galaxies with AGN remains uncertain, a comprehensive identification of AGN in these populations is necessary to obtain meaningful results. The dust content to each population is also derived by correlating UV and Radio SFRs, giving a higher obscuration for more active SF sources. Also, know to be amongst the most massive galaxies in the high-z universe, I will show that ERGs may constitute up to 60% of the total mass in the universe at 1 ≤ z ≤ 3. Finally, preliminary and promising results are presented on the morphologies of ERGs (CAS and Gini/M20 parameters) based on the v1.9 ACS GOODS-S images.
AbstractDespite speculation that both starburst and nuclear activity in galaxies may be intimately linked via the common triggering mechanism of mergers and interactions, very little is known about the true nature of the link. Thus, the role of AGN in the formation and evolution of galaxies is still not well established. I will present deep Gemini/GMOS imaging observations which are used to investigate the triggering mechanism(s) in a complete sample of radio-loud AGN for which, uniquely, we have quantified the level of both the AGN and star formation activity. I will show results on the proportion of powerful radio galaxies triggered in galaxy mergers and also on the link between the degree of star formation/AGN activity and the interaction status of the host galaxies.
AbstractWe present the results of our systematic search for optically elusive, but intrinsically luminous buried AGNs in >100 nearby (z < 0.3) luminous infrared galaxies with L(IR) > 1011 L⊙, classified optically as non-Seyferts. To disentangle AGNs and stars, we have performed (1) infrared 2.5-35 μ low-resolution (R ~ 100) spectroscopy using Subaru, AKARI, and Spitzer, to estimate the strengths of PAH (polycyclic aromatic hydrocarbon) emission and dust absorption features, (2) high-spatial-resolution infrared 20 micron imaging observations using Subaru and Gemini, to constrain the emission surface brightnesses of energy sources, and (3) millimeter interferometric measurements of molecular gas flux ratios, which reflect the physical and chemical effects from AGNs and stars. Overall, all methods provided consistent pictures. We found that the energetic importance of buried AGNs is relatively higher in galaxies with higher infrared luminosities (where more stars will be formed), suggesting that AGN-starburst connections are luminosity dependent. Our results might be related to the AGN feedback scenario as the possible origin of the galaxy down-sizing phenomenon.
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