Found 22 talks width keyword star forming galaxies

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Thursday May 27, 2021
Dr. Manuela Bischetti
INAF/Trieste

Abstract

This talk will be dedicated to luminous (LBol~1E47 erg/s),
high-redshift quasars, which are ideal targets to investigate (i) feedback
from SMBHs, and (ii) the early growth phases of giant galaxies. I will
present evidence of  SMBH-driven outflows  at all Cosmic epochs, back to
the early Universe. These outflows involve all gas phases (molecular,
neutral, ionised) and extend on nuclear to galactic and circum-galactic
scales. I will report on the first systematic study of the molecular gas
properties in the host-galaxies of the most luminous quasars, fundamental
to probe the impact of SMBH feedback on the host-galaxy evolution. I will
show that luminous quasars pinpoint high-density sites where giant galaxies
assemble, and I will discuss the major contribution of mergers to the final
galaxy mass. To this aim, I will present a wealth of multi-wavelength (UV
to sub-millimeter) observations from the WISE/SDSS hyper-luminous quasars
survey  at z~2-5 (WISSH), and recent results from the ESO large program
XQR-30, the Ultimate X-SHOOTER Legacy Survey of Quasars at the Reionization
epoch.

 


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Thursday June 13, 2019
Dr. Jorge Sanchez Almeida
IAC

Abstract

Although the name 'fundamental metallicity relation' (FMR) may sound a bit bombastic, it really represents a fundamental relation in the sense of revealing a fundamental process in galaxy formation. Numerical simulations predict that accretion of cosmic web gas feeds star formation in star-forming galaxies. However, this solid theoretical prediction has been extremely elusive to confirm. The FMR, i.e., the fact that galaxies of the same stellar mass but larger star formation rate (SFR) tend to have smaller gas-phase metallicity (Zg), is one of the best observational supports available yet. The talk will introduce the FMR and then present recent results of our group showing how the FMR emerges from a local anti-correlation between SFR and Zg existing in the disks of galaxies. Thus, understanding the FMR is equivalent to understanding why active star-forming regions tend to have low relative metallicity. The existence of the local anti-correlation SFR-vs-Zg is found by Sanchez-Menguiano+19 ApJ  and Sanchez Almeida+18 MNRAS, whereas the equivalence between local and global laws is in Sanchez Almeida & Sanchez-Menguiano 19 ApJL.


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Tuesday January 8, 2019
Dr. Johan Knapen
IAC

Abstract

We present the discovery of a small 0.2'' (60 pc) radius kinematically decoupled core, as well as an outflow jet, in the archetypical AGN-starburst "composite" galaxy NGC 7130 from integral field data obtained with the adaptive optics-assisted MUSE-NFM instrument on the VLT. Correcting the already good natural seeing at the time of our science verification observations with the four-laser GALACSI AO system we reach an unprecedented spatial resolution of around 0.15''. We confirm the existence of star-forming knots arranged in an 0.58'' (185 pc) radius ring around the nucleus, previously observed from UV and optical  Hubble Space Telescope and CO(6-5) ALMA imaging. We determine the position of the nucleus as the location of a peak in gas velocity dispersion. A plume of material extends towards the NE from the nucleus until at least the edge of our FOV at 2'' (640 pc) radius which we interpret as an outflow jet originating in the AGN. The plume is not visible morphologically, but is clearly characterised in our data by emission lines ratios characteristic of AGN emission, enhanced gas velocity dispersion, and distinct non-circular gas velocities. Its orientation is roughly perpendicular to line of nodes of the rotating host galaxy disk. An 0.2''-radius circumnuclear area of positive and negative velocities indicates a tiny inner disk, which can only be seen after combining the integral field spectroscopic capabilities of MUSE with adaptive optics.


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Thursday February 26, 2015
Dr. Julie Wardlow
Dark Cosmology Centre (Copenhagen)

Abstract

 

Over the past ~20 years the high-redshift Universe has been increasingly opened to scrutiny at far-infrared wavelengths, where cool dust emission from star-formation dominates. The dusty star-forming galaxies (DSFGs) and submillimeter galaxies (SMGs), selected at these wavelengths likely represent an important, but short-lived phase in the growth of massive galaxies. These DSFGs often have star-formation rates in excess of ~1000 solar masses per year and are confirmed out to at least z~6, although their redshifts and high dust contents make them faint and difficult to study at other wavelengths. Now, using data from the Herschel Space Observatory we have identified a population of DSFGs that are strongly gravitationally lensed and therefore magnified and available for unprecedented multi-wavelength scrutiny. I will describe how this important gravitationally lensed population is identified, and present and interpret the data from our extensive multi-wavelength, multi-facility follow-up studies. I will also present follow-up observations of an intriguing sample of the highest redshift DSFGs (z>4) that are also selected via Herschel data, and that are proving troublesome to explain in galaxy formation simulations.

 


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Wednesday October 29, 2014
Dr. Daniel Ceverino
Dept. Física Teórica - Universidad Autónoma de Madrid

Abstract

Any successful model of galaxy formation needs to explain the low rate of star formation in the small progenitors of today’s galaxies. This inefficiency is necessary for reproducing the low stellar-to-virial mass fractions. A possible driver of this low efficiency is the radiation pressure exerted by ionizing photons from massive stars. The effect of radiation pressure in cosmological, zoom-in galaxy formation simulations is modelled as a non-thermal pressure that acts only in dense and optically thick star-forming regions. The main effect of radiation pressure is to regulate and limit the high values of gas density and the amount of gas available for star formation. By using these simulations, I will address the early formation of compact spheroids by violent disc instabilities (VDI). Due to the inefficiency of star formation, this process is gas rich, so the dissipation naturally leads to compact spheroids. These VDI-driven spheroids, much like merger-driven spheroids, have steep surface density profiles, consistent with a classical, de-Vaucouleurs profile at all times.


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Thursday May 29, 2014
Dr. Jorge Sanchez Almeida
IAC

Abstract

This paper discusses how cosmic gas accretion controls star formation, and summarizes the physical properties expected for the cosmic gas accreted by galaxies. The paper also collects observational evidence for gas accretion sustaining star formation. It reviews evidence inferred from neutral and ionized hydrogen, as well as from stars. A number of properties characterizing large samples of star-forming galaxies can be explained by metal-poor gas accretion, in particular, the relationship between stellar mass, metallicity, and star formation rate (the so-called fundamental metallicity relationship). They are put forward and analyzed. Theory predicts gas accretion to be particularly important at high redshift, so indications based on distant objects are reviewed, including the global star formation history of the universe, and the gas around galaxies as inferred from absorption features in the spectra of background sources.


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Thursday December 19, 2013
Dr. Daniel Rosa
Instituto Nacional de Astrofisica, Optica y Electronica, Mexico

Abstract

I will present the first Large Millimiter Telescope spectra of 4 nearby galaxies with known high star formation rates. The individual spectra were acquired with the Redshift Search Receiver, a 3 mm spectrograph that covers simultaneously the 3 mm band from 75 to 110 GHz. The spectra show rms temperatures of around 4 mK that allow us to detect not only common molecular species such as CO, HCN, HCO+, HCN, 13CO reported widely in the literature but also other more rare molecular transitions (HC3N, CN, CH3OH, CH3C2H) and even Hydrogen recombination lines (from H39alpha to H42alpha). We are making use of theoretical radiative transfer models to analize these spectra in order to understand the variations of the observed line ratios of different lines in galaxies classified as ultraluminous infrared galaxies where the star formation rate may be as high as 100 solar masses per year. These data will help to understand the physical conditions of the gas in regions that are forming stars very efficiently. The observed line ratios in star forming galaxies are also compared to those galaxies that is known to contain an AGN.


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Thursday December 5, 2013
Dr. Sandesh Kulkarni
MPIE, Garching, Germany

Abstract

 How does the group environment hamper star-formation in star-forming galaxies?

Abstract: We present the first results from the H-alpha Galaxy Groups Imaging Survey (HAGGIS), a narrow-band imaging survey of SDSS groups at z < 0.05 conducted using the Wide Field Imager (WFI) on the ESO/MPG 2.2 meter telescope and the Wide Field Camera (WFC) on the Issac Newton Telescope (INT). In total, we observed 100 galaxy groups with wide range of halo mass 10^12 - 10^14 M_sun in pairs of narrow-band filters selected to get continuum subtracted rest-frame H-alpha images for each galaxy in these groups. The excellent data allows us to detect H-alpha down to the 10^(-18) ergs/s/cm^2/arcsec^2 level. Here, we examine the role played by halo mass and galaxy stellar mass in deciding the overall star formation activity in star forming disks by comparing stacked H-alpha profiles of galaxies in different halo mass and stellar mass bins. With this preliminary study, we have found that the star-formation activity in star-forming galaxies decreases in larger halos compared to the field galaxies. Using median equivalent width profiles, we can infer how environmental processes affect star-forming galaxies differently at different radii.


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Thursday October 17, 2013
Dr. B-G Anderson
SOFIA Science Center-USRA

Abstract

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is now performing scientific observations and the results of the second open observing cycle solicitation is about to be announced.  With an available wavelength coverage from the visual to sub-mm wavelengths and a long life time - including planned instrument upgrades, SOFIA will provide critical resource for the astronomical community for the next decade and beyond.  Current and expected SOFIA instruments provide heterodyne spectroscopy in the THz band, including the line of [O I], [C II] and [N II] as well as OH, HD and many other hydrides, at high spectral resolution.  Echelle spectroscopy in the Mid-infrared (MIR) which will allow observations of e.g. fine-structure lines of and H2 pure rotational lines.  These will help address questions of interstellar chemistry and physics in star forming regions, PDRs and galaxies.  Mid-infrared (MIR) grism spectroscopy, of e.g. dust and ices, can be used to address questions of the freeze-out of molecules from the gas phase to better understand the formation, destruction and characteristics of interstellar ices.  Imaging in the MIR and FIR and FIR polarimetry can provide a more complete picture of the temperature, density and magnetic field structure of e.g. star forming cores. I will highlight the current and expected capabilities of SOFIA and some of the early science results achieved.


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Tuesday February 19, 2013
Dr. Helena Domínguez Sánchez
IAC

Abstract

In this talk we will show the evolution of high-redshift (z≥ 1.4) quiescent galaxies in the COSMOS field. We have studied an IRAC (mag 3.6 μm < 22.0) selected sample of ~ 18 000 galaxies at z≥ 1.4 in the COSMOS field with multiwavelength coverage extending from the U band to the Spitzer 24 μm one. We have derived accurate photometric redshifts and other important physical parameters [masses, ages and star formation rates (SFR)] through a SED-fitting procedure. Galaxies have been divided according to their star formation activity into actively star-forming, intermediate and quiescent galaxies depending on their specific star formation rate (sSFR = SFR/M). The evolution of the Galaxy Stellar Mass Funtion (GSMF) of the different populations, in particular of the quiescent galaxies, has been investigated in detail. There is a significant evolution of the quiescent stellar mass function from 2.5 < z < 3.0 to 1.4 < z < 1.6, increasing by ~1 dex in this redshift interval. We find that z ~1.5 is an epoch of transition of the GSMF: while the GSMF at z≳ 1.5 is dominated by the star-forming galaxies at all stellar masses, at z≲ 1.5 the contribution to the total GSMF of the quiescent galaxies is significant and becomes higher than that of the star-forming population for M≥ 1010.75 Msun. We derive the fraction of quiescent/star-forming galaxies with redshift, as well as the stellar mass density. We also compare our results with the predictions of theoretical models. Finally, I will introduce my current project: studying in deeper detail the IRAC drop-outs of the sample with new nIR (ULTRA-VISTA) and fIR (Herschel) data to elucidate between very dust-obscured objects or high-z star forming galaxies, which could help us to put some constrains to the high-mass end of the GSMF at high-z.


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