INAF - Osservatorio Astronomico di Padova

L' INAF - Osservatorio Astronomico di Padova è una struttura di ricerca dell'Istituto Nazionale di Astrofisica. L' attività principale dell'istituto è la ricerca scientifica nei vari campi dell'astrofisica, inclusa la progettazione e lo sviluppo di tecnologie innovative per strumentazione astronomica d’avanguardia. L'Osservatorio di Padova favorisce inoltre la diffusione della cultura scientifica grazie a progetti di didattica e divulgazione dell’Astronomia che si rivolgono alla Scuola e alla Società. 

21 Marzo - 30 Settembre 2017: Rassegna per le celebrazioni dei 250 anni della Specola

In evidenza

The study concerns with the emission from dust in galaxies in the approximate wavelength range from 10-1000 micron. It combines Spitzer, Herschel and Planck satellite data in order to build a detailed picture of the interaction between star formation and far-infrared emission in nearby galaxies. Understanding the infrared emission from nearby galaxies is of particular interest because star forming galaxies can often only be observed at very large distances in this waveband. Therefore, if we are to understand the very distant, very young objects, that we see in the early Universe, we must first understand those that are close enough to permit detailed study.

Figure 1: component modified black body fits to some example galaxies selected from the Planck Early Release Compact Source Catalogue.

Person: Marcel Clemens, Gianfranco DeZotti, Mattia Negrello, Roberto Rampazzo.
Collaborators: L. Bonavera, Joaquin Gonzales Nuevo, L. Danese, J. Davies.

Recent publication: Negrello M., et al., 2013, MNRAS, 429, 1309; Auld R., et al., 2013, MNRAS, 428, 1880; Davies J.I., et al., 2013, MNRAS, 428, 834; Davies J.I., et al., 2012, MNRAS, 419, 3505; Clemens M.S., Panuzzo P., Rampazzo R., Vega O., Bressan A., 2011, MNRAS, 412, 2063; Baes M., et al., 2010, A&A, 518, L53; Clemens M.S., et al., 2010, A\&A, 518, L50

We performed a large set of  simulations of galaxy encounters using a smooth particle hydrodynamic (SPH) code implemented with chemo-photometric evolutionary population synthesis models. Our simulations start from the same initial conditions as described in Mazzei & Curir (2003), i..e. collapsing triaxial systems  composed of dark matter (DM) and gas in different proportion and different total mass. Each simulation self-consistently provides morphological, dynamic and chemo-photometric evolution. The spectral energy distribution (SED) extends over four order of magnitude in wavelenght, i.e. from 0.06 micron to 1 mm including extinction and re-emission by dust.  All the model parameters had been tuned in previous works.

Our simulations, which best-fit the global properties of several local galaxies, give insight into their evolutiom. We analyzed  a polar ring galaxy, ESO474-G26 (Spavone et a. 2012), and galaxies of different morphological types in groups, like the early-type galaxy (ETG) NGC3934 and its spiral companion NGC3933 (Bettoni et al. 2011) in the NGC3934 group. We focused on the evolution of the central regions of the NGC1023 large group (Bettoni et al. 2012), and on the central galaxies of two local poor groups: NGC4756 and NGC5328 (Trinchieri et al. 2012), giving also consistent predictions of their X-ray emission. Recently, we highlight the evolution of eight ETGs in the U376 and LGG225 groups, both  in the Leo cloud (Mazzei et al. 2104a) and of  two S0 galaxies, NGC3626 and NGC1533. NGC1533, in particular,  shows a very peculiar UV morphology, well matched by our simulation of a major merger (mass ratio 2:1) as in the figure below  (Mazzei et al 2014b).

NGC1533 figura finale

For the first time, we outlined the evolution of galaxies in the rest-frame UV color - absolute magnitude diagram, i.e., NUV-r versus Mr [AB] absolute magnitude. The transition from the blue sequence to the red sequence in this diagram (figure below, blue lines) lasts about 4 Gyr and corresponds to a morphological transformation from late-type disk galaxies to ETGs, as in the case of all the bright ETGs diagram in  the U376 group we simulated (red points in the diagram below, Mazzei et al. 2014a).

CDM U376

People:   Paola Mazzei

Collaborators: D. Bettoni, L. Buson, R. Rampazzo, (INAF, OAPd); A. Marino and G. Galletta (UniPd); Trinchieri, G. and Wolter, A. (Brera, INAF)

Recent pubblications: Bettoni et al (2011), A&A, 534, 24;  Bettoni et al. (2012), MNRAS, 423, 2957;  Spavone et al. (2012), MNRAS, 426, 2003; Trincheri et al (2012), A&A 545, 140; Marino et al. (2013), MNRAS, 428, 476; Mazzei et al. (2014a), ApJ 782, 53; Mazzei et al (2014b), AdSpR 53, 920


Spectral classification and Dynamical properties

We measured fluxes and intensity ratios of emission lines in the visible region of the spectrum (λ4000−9000 Å) for 75 galaxy members of the IDS (Infrared Deep) Sample.

The spectral classification of 42 galaxies, with the emission line ratio diagnostic diagrams, shows that the NEPR sample is predominantly
composed of starburst galaxies (71%),  while the fraction of LINERs (21%) and AGNs (7%) is small. Three new Sy 1 galaxies were identified,
3-44A1, 3-70A, and 3-96A.
The rest-frame FIR luminosity distribution of galaxies with spectral classification spans the same range as the FIR-selected complete sample analyzed by Mazzei et al. (2007), i.e. three orders of magnitude, with the same mean value, log(LFIR) = 10.2. This emphasizes that such galaxies represent FIR properties of the whole sample well. Moreover, their optical properties are typical of the sample itself since 62% of these belong to the 60 μm selected complete sample of galaxies defined by Mazzei et al. (2001).
Using the rotation curves and spatially resolved, low resolution spectra, we are able to derive dynamical parameters of
41 galaxies and mass estimates, inside the last point viewed, of 39 galaxies in the sample  (left figure below), 67% of them belong to the complete sample defined above. Moreover, their rest-frame FIR luminosity distribution (right figure below) extends over the same range and with the same average luminosity value (log FIR=10.3) as expected for the complete sample.

 Figura nepr

48% of  our rotation curves have disturbed morphologies and most corerspond to star forming galaxies. This emphasizes the role of interactions in triggering starbursts, and, in particular, FIR emission  in our sample of dusty galaxies.

People:   Paola Mazzei, Daniela Bettoni, Antonio della Valle

Collaborations: Antonietta Marino and Giuseppe Galletta (Univ di Padova), Roberto Rampazzo

Recent pubblications: Bettoni et al (2012), A&A, 538, 72

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