Every 2nd or 3rd Monday of the month, 10AM
Organisors: Tessel van der Laan (IRAM Grenoble) & Carsten Kramer (IRAM Granada)
Open slots: 12th May, 15th September, 20th October, 17th November, 8th December
16th June: Gaelle Dumas (Grenoble)
TUESDAY 15th April (3pm): Denis Barkats (Visitor talk Grenoble)
Title: Detection of B-mode polarization at degree angular scales using BICEP2
I will present the recently reported detection of B-modes in the CMB polarization by the BICEP2 experiment. BICEP2 was a CMB polarimeter specifically designed to search for the elusive signal from inflationary gravitational waves in the B-mode power spectra around l = 80. BICEP2 has accumulated 3 years of data from the South Pole from 2010 to 2012, integrating continuously on a low-foreground region of effective size 1% of the whole sky. I will describe the experimental strategy, tests for foreground or systematics contamination, and results in the map and power spectra. The reported B-mode spectrum is well fit by a lensed-LCDM plus tensor theoretical model with tensor/scalar ratio r = 0.20 +0.07 -0.05 with r = 0 disfavored at 7 sigma.
POSTPONED (17th March): PHIBSS (Grenoble)
Due to scheduling problems at Grenoble and a broken projector system this talk will be postponed. New date to follow.
17th February: Israel Hermelo (Granada)
Title: Interstellar dust in dwarf galaxies
We are carrying out a study of the interstellar dust in star-bursting dwarf galaxies from the perspective of the emission of dust grains. We chose this kind of objects because they are simple systems driven by a few star forming regions that dominate the emission and because their dust properties have been a matter of debate over the last decade. In particular, the strong excess at the (sub)mm range has lead to the assumption that dust properties are different from what we observe in spiral galaxies.
To analyse the observational SEDs of our sample of dwarf galaxies we used two radiation transfer models to study separately the emission from the star forming regions and from the diffuse dust. This is the first time a full radiation transfer analysis constrained by the observed SEDs of spatially separated components has been done for dwarf galaxies. Both models make use of "normal" dust properties.
In general, we achieved a good agreement between data and models, both for the diffuse dust emission and the dust in HII+PDR regions. The global gas-to-dust mass ratios derived from the modeling are compatible with their expected values from their metallicities. Our results do not show clear evidence of the need of different dust properties.
6th February: Heino Falcke (Visitor talk Grenoble)
Title: Towards Imaging the Event Horizon in the Galactic Center
Black holes are supposed to power the nuclei of galaxies. The best place to test this paradigm is the Galactic center. Here a compact radio source, Sgr A*, with a mass of 4 Million solar masses marks the very center of our Galaxy. Numerical magnetohydrodynamic simulations and semi-analytic models seem to converge towards a combined jet-disk model producing radiation from radio to X-rays to explain the emission. Interestingly, radio interferometry and timing observations are now probing the smallest scales of this object, directly confirming that the high-frequency radio emission indeed comes from event-horizon scales. This allows one to study basic astrophysical processes such as jet formation and accretion physics. Using future mm-VLBI experiments it should be possible to even image the elusive event horizon of a black hole for the very first time. This “Event Horizon Telescope” can turn Sgr A* into a fundamental laboratory for precision black hole astrophysics.
20th January: Pedro Paulo Beaklini (Grenoble)
Title: Radioastronomy in Brazil: past, present and future
Abstract: In this talk I will present a briefly overview of the Brazilian Radioastronomy. First, I will show the most important works realized in the Itapetinga Radio Telescope, the first radome enclosed observatory at centimeter wavelengths, the detection of the first water megamaser, the Orion line variability, the Solar studies, and the maps of the 3C273 jet, when Itapetinga was integrated in the VLBI network. In the late 80s, the number of citations in Radio Astronomy in Brazil was equivalent to 5% of all citations in science of the University of São Paulo. At present epoch, the recently publications that used the Itapetinga Radio Observatory are results of the monitoring of the continuum emission of variable radio sources at 43 GHz: Centaurus A, Eta Carinae, quasars and SgrA* - It was the first time that the radio variability of SgrA* was observed using a single dish instrument. I will show all the light curves and list the main results. The future of radioastronomy in Brazil consists in a new instrument: LLAMA (Long Latin America Milimetric Array). It will be like an APEX antenna that will be installed in partnership with Argentina and that can be used simultaneous with ALMA and others VLBI networks. Beyond LLAMA, there is also a possibility of Itapetinga integrates the eVLBI project. At last, if Brazil really becomes an ESO member, it should be open an ARC Node in São Paulo.
13th January: Jonathan Braine (Visitor talk Grenoble)
Title: Molecular gas and Star Formation in M33
Abstract: M33 is a small spiral galaxy in the Local Group, at about 840 kpc. I will present some results from the recently completed IRAM Large Program to completely map M33 in the CO(2-1) line. The data reduction and production of moment maps of such a large dataset required considerable care, particularly to assess the effect of the error beam, and this will be discussed. The goals of the project are multiple:
- identify the Giant Molecular Clouds in M33, their mass spectrum and their basic properties
- make real progress on determining the NH2/Ico ratio and how it varies
- measure the CO-HI velocity dispersion
- obtain a GMC-scale column density distribution (pdf) of the molecular gas
- study the conditions in the molecular gas comparing with CO(3-2) and CO(1-0) data
- measure Far-IR SEDs of GMCs, looking for a difference in the dust between the molecular and
- atomic gas
- study the association between clouds (CPROPS GMCs) and young stellar clusters
25th November: Karin Oberg (Visitor talk Grenoble)
Title: Icy origins: snowlines during star and planet formation
In the cold and dense stages of star and planet formation, volatile molecules condense out on interstellar grains forming icy mantles. This condensation process results in a series of snowlines, or condensation fronts, whose exact locations are set by a combination of thermal and non-thermal adsorption and desorption processes. The icy grain mantles are also active chemical sites, resulting in a changing ice composition with time, typically to include an increasing fraction of complex organic molecules. The nature of these snowlines in protoplanetary disks are predicted to have large impacts on planet formation efficiencies, on the bulk compositions of the forming planets, and on the amount of prebiotic material available on planet surfaces. We have used a combination of IR and millimeter observations, theory, and laboratory experiments to characterize interstellar ices, snow line locations (i.e. where these ices are located), and the chemical and planet formation consequences of the exact locations of different snow lines. I will discuss how the outcome of these studies have impacted our understanding of ice formation during star and planet formation, and also future prospects as complete ALMA and the next generation of laboratory experiments come online.
14th October: Sergio Martin (Grenoble)
Title: Chemistry in (extra-)galactic centers at Galactic center resolution
Chemical studies in external galaxies are reaching the resolution and complexity previously reserved to Galactic studies. I will go through some of the key studies of the last decade concerning extragalactic chemistry and some of the chemical diagnostics proposed so far. By observing the progress in molecular observations during the last years one can foresee what to expect in the nearby future. Some galactic center results at sub-parsec resolution will be presented. The Galactic center, being the closest galaxy center, is no doubt the best test laboratory to understand the chemistry in external galaxies.
23rd September: Simona Gallerani (Visitor talk Grenoble)
Title: Far infrared emission lines in quasars and galaxies at the epoch of cosmic reionization
Far infrared (FIR) emission lines (e.g. [CII] at 158 micron, [NII] at 205 micron, CO(J=2-1) at 115GHz) have opened up a new window for studying the high redshift Universe, since they represent powerful tools for detecting and characterizing very distant galaxies. In my talk I will present both observations and simulations of FIR lines in z~6 quasars and galaxies.
First, I will show PdBI observations of FIR lines in a lensed quasar at z=4.4. Through the combined detection of the [CII], [NII], and CO(5-4) lines, I will discuss how it is possible to constrain several properties of the interstellar medium in this object, namely the gas density and metallicity, and the radiation field intensity. Moreover, I will show the detection of broad wings in the [CII] line emitted by one of the most distant quasar known (z=6.4). The extent of the wings and the size of the [CII] emitting region associated to them, are indicative of a QSO-driven massive outflow at the epoch of cosmic reionization with the highest outflow rate ever found.
Up to now, z>4 detections of FIR lines have been obtained mainly in galaxies hosting AGN or with high star formation rates. In principle, the unprecedented sensitivity of ALMA would allow the detection of FIR lines even from “normal” population of high-z galaxies, such as Lyman Alpha Emitters. However, these kind of experiments have been so far unsuccessful. I will present radiative transfer simulations adopted to derive the expected intensity of several FIR lines emitted by high-z LAEs. These calculations can be used to device novel strategies to detect high-z normal galaxies through FIR lines. In particular, I will provide the required observing time for detecting z=6-7 LAEs as a function of their metallicity.
8th July: Samuel Leclercq (Grenoble)
NIKA at the 30m telescope in June 2013; a new dual band continuum instrument soon available for astronomy
A few years ago IRAM started a project to replace the former bolometer instrument by a significantly more powerful instrument. NIKA, the New IRAM KID Array is a prototype that has been developed since 2009 in this framework. It is based on a new technology using Kinetic Inductance Detectors instead of bolometers. During its evolution NIKA has been tested several times on the sky at the IRAM 30m telescope. For the latest run, in June 2013, we had about 130 pixels at 150 GHz with a very good sensitivity and 200 pixels at 250 GHz with a sensitivity not as good as expected but sufficient to start doing some interesting astronomy. We foresee to open this prototype to the astronomers community for the next semester, so my talk will be specifically oriented in this direction: I will briefly present NIKA for those who don't know it yet, then I'll speak about the latest run, showing some very preliminary results and describing the present capacities of this instrument. There will be time for questions so that you can start imagining projects you could conduct with NIKA.
10th June: Florie Teste (Granada)
Title: Spatial distribution of protostars in the galactic plane
We know that giant molecular clouds host sites for stellar formation. However, the mechanism leading to the star formation are still debated. The Herschel space telescope will provide some clues to answer this question, by mapping dust and potential sites for (massive) star formation.
Herschel is also sensitive to the environment of nascent stars (molecular gas, HII regions, OB associations, Supernova remnants, etc.) which may influence star formation processes.
I will present the results obtained during my master degree internship, performed during the last 3 months with Dr. Nicolas Billot. We studied the distribution of early stages of star formation, thanks to the Hi-GAL (a key project of the Herschel space observatory) data. We started by studying the source catalogues to check their integrity, before performing a Minimum Spanning Tree analysis. Our goal is to obtain some statistics on the clustered structures detected in the Inner Plane. Then we search for correlations between the identified clusters and HII regions which may have triggered events of star formation.
13th May: Sabine Koenig (Grenoble)
Title: The anatomy of polar ring minor merger systems: NGC 1614
The focus on merger studies often lies on major mergers and their evolution, although minor mergers likely constitute the bulk of interactions. Understanding how gas is feeding starburst and AGN activities in these objects is hence of paramount to understand the overall evolution of the Universe. This project will consider the nature of central gas structures in a hierarchy of merger scales as a means to understand how central gas properties and mergers relate. The emphasis is on studying selected objects so as to allow detailed observations. Only in a nearby minor merger is it possible to study in detail the underlying physics that govern these events. NGC 1614 and NGC4194 are excellent examples of minor mergers with spectacular morphology and intense nuclear starburst. I will especially concentrate on NGC 1614: While a galaxy interaction is the overall trigger, the precise cause of the starburst is unknown - it is either dynamically induced at a Lindblad resonance or by a "wildfire" event.
22th April: Sandra Trevino (Granada)
Title: Study of deuterated molecules in the PDR around the UCHII region Mon R2
Photon-dominated regions (PDRs) are ubiquitous environments where chemistry and heating are driven by UV photons from nearby O & B stars. The massive star forming region MonR2 is the closest (830 pc) ultracompact (UC) HII region associated with a PDR. We are carrying out a spectral line survey of the PDR associated with MonR2 using both ground and space based facilities, with the aim of investigating the chemistry of the molecular gas around the UCHII region and the possible variations due to the different local physical conditions. In January 2012 we performed an unbiased ~64 GHz spectral survey at 1 mm (202.3–265.2 GHz), and discovered an unexpectedly rich chemistry. In July 2012 we performed surveys at 3 mm, to complete the work of Ginard et al. (2012), and at 2 mm, to observe promising deuterated species. More than thirty different species (including isotopologues and deuterated compounds) were detected. These observations permit to derive the physical parameters, as well as to perform a chemical comparison between the most significant positions of the UCHII region and the PDR.
16th April: Vincent Pietu (Grenoble)
Title: the possibilities of self-calibration within the gildas software
No abstract given
15th April: Monica Rodriguez (Visitor talk Grenoble)
Title: Molecular gas in active galaxies
I will present an ongoing study to determine the physical characteristics of the molecular gas in active galaxies. For this, we have made use of three transitional lines of the formaldehyde molecule (H2CO) at 218.22GHz, 218.76GHz and at 145.6GHz. Formaldehyde has proven to be a useful tracer of the temperature and density in Galactic molecular clouds and external galaxies, besides it seems to be a more unambiguous tracer as compared to the most "popular" high density tracers. I will show very preliminary results of H2CO observations taken with the 30m IRAM telescope toward a sample of starburst and AGN galaxies.
21th March: Philippe Raffin (Grenoble)
Title: The Greenland Telescope Project: Antenna retrofit for mm and sub-mm VLBI operations
We propose to deploy the ALMA-NA 12m Prototype Antenna, after appropriate retrofitting and improvements, to the summit of the Greenland icecap, for the purpose of millimeter (mm) and submillimeter (submm) wavelength Very Long Baseline Interferometry (VLBI). The scientific objective is to resolve the image of a super massive black hole (SMBH). This presentation will focus on the antenna retrofit.
11th March: Jerome Pety (Grenoble)
Title: Bright 12CO(1-0) emission also traces diffuse gas
Summarizing 20 years of efforts, I will quantify the global average CO luminosity and CO-H2 conversion factor applicable to diffuse but partially molecular ISM when H2 and CO are present but C+ is the dominant form of gas-phase carbon. Perhaps surprisingly, the mean ratio of integrated CO brightness to N(H2) does not differ from the usual value of 1 K.km/s of integrated CO brightness per 2.10^20 H2.cm-2. Commonality of the CO-H2 conversion factor in diffuse and dark clouds can be understood from compensating effects of CO radiative transfer and chemistry.
I will also relate the degree-scale structure of galactic diffuse clouds to sub-arcsecond absorption spectra using 1' resolution ARO 12m telescope maps of CO emission around 11 absorption line background sources. As with FERMI and PLANCK there is some gas that is dark in CO and other gas in which CO is overluminous per H2. Typical covering factors of individual features at the 1 K.km/s level are 20% and Wco/N(H2) ratios as much as 4-5 times above the mean value 1 K.km/s per 2e20 H2 cm^-2 are found. In this way a standard CO-H2 conversion factor applies overall owing to balance between the luminosities per H2 and surface covering factors of bright and dark CO. Variability of the CO brightness and CO-H2 conversion factor are due primarily to CO chemistry and need not represent equivalent variations in N(H).
There is unavoidable confusion between CO emission from diffuse and dark gas and misattribution of diffuse CO emission to clouds on the verge of star formation. As an example, I will briefly report on the Plateau de Bure Arcsecond Whirlpool Survey (PAWS) that aims to image for the first time the CO emission of molecular gas in a grand design spiral at a spatial resolution of about 40pc matching the typical size of Giant Molecular Clouds. Indeed, PAWS reveals that the total flux is about equally divided between two components: a weak but broad-lined component structured at spatial scales wider than 12arcsec ~ 0.5kpc and a brighter, narrower-lined more compact component. We interpret the former as a thick disk of diffuse molecular gas.
11th February: CANCELLED Jerome Pety (Grenoble)
21th January: Jorge Abreu (Granada)
Title: Properties of gas and dust in M33: C+, CO, HI, and far-infrared observations
In this work, the important gas cooling line [CII] at 158 micron is used to study the heating of the gas in the major axis of the nearby Local Group Galaxy M33. The ratio [CII]/far-infrared cont is used as a proxy for the heating efficiency. With this ratio we study the variation of the photoelectric heating efficiency with the galactic environment. A model of photon-dominated regions was used to calculate the physical conditions of the observed gas.
14th January: Tessel van der Laan (Grenoble)
Title: Circumnuclear star forming rings
The secular evolution of galaxies is especially noticeable in their central kiloparsecs where the dynamical timescales are much shorter than at larger radii. Large scale bars and circumnuclear (resonance) rings are important features that drive this evolution. Circumnuclear rings are believed to be very effective barriers for gas inflow to the nucleus and can thus contain large amounts of gas. In the central kiloparsec, most gas is in molecular form. The high densities that molecular gas can reach in these rings, leads to rapid and extreme star formation events. The total effect circumnuclear starburst rings have on secular evolution depends on the longevity of the rings and their ability to replenish themselves with gas.
In this talk I will discuss my recent PhD work on the circumnuclear starburst rings in two nearby barred spiral galaxies, NGC 5248 and NGC6951. Together, NGC 5248 and NGC 6951 form a complementary pair. While NGC 6951 exhibits a Seyfert 1/LINER nucleus inside its circumnuclear ring, NGC5248 has no AGN but has two(!) circumnucear starforming rings, one at 370pc and one at 100pc radius. I will present PdBI+30m CO emission line observations of molecular gas in and around the circumnuclear rings in both galaxies in combination with HST imaging and optical integral-field spectroscopy data probing the stellar population in the central kiloparsec. The observed gas kinematics and derived age distribution of the stellar populations of the rings provide insights into their formation/evolution. I also obtain an estimate for the lifetime of the ring for the oldest observed stellar populations, which implies a minimum lifetime for the large scale bar as well.
10th December: CANCELLED Jorge Abreu (Granada)
12th November: Pierre Gratier (Grenoble)
8th October: Christof Buchbender (Granada)
10th September: Viviana Guzman (Grenoble)