Spitzer/IRS Mapping of Local Luminous Infrared Galaxies

We present results of our program Spitzer/IRS Mapping of local Luminous Infrared Galaxies (LIRGs). The maps cover the central 20"x20" or 30"x 30" regions of the galaxies, and use all four IRS modules to cover the full 5-38 microns spectral range. We have built spectral maps of the main mid-IR emission lines, continuum and PAH features, and extracted 1D spectra for regions of interest in each galaxy. The final goal is to fully characterize the mid-IR properties of local LIRGs as a first step to understanding their more distant counterparts.Comment: 4 pages, 5 figures. To appear in "Highlights of Spanish Astrophysics V", Proceedings of the VIII Scientific Meeting of the Spanish Astronomical Society (SEA) held in Santander, 7-11 July, 200

Warm molecular gas temperature distribution in six local infrared bright Seyfert galaxies

We simultaneously analyze the spectral line energy distributions (SLEDs) of CO and H2 of six local luminous infrared (IR) Seyfert galaxies. For the CO SLEDs, we used new Herschel/SPIRE FTS data (from J=4-3 to J=13-12) and ground-based observations for the lower-J CO transitions. The H2 SLEDs were constructed using archival mid-IR Spitzer/IRS and near-IR VLT/SINFONI data for the rotational and ro-vibrational H2 transitions, respectively. In total, the SLEDs contain 26 transitions with upper level energies between 5 and 15000 K. A single, constant density, model (n$_{H_2}$ ~ 10$^{4.5-6}$ cm$^{-3}$) with a broken power-law temperature distribution reproduces well both the CO and H2 SLEDs. The power-law indices are $\beta_1$ ~ 1-3 for warm molecular gas (20 K < T 100 K). We show that the steeper temperature distribution (higher $\beta$) for hot molecular gas can be explained by shocks and photodissociation region (PDR) models, however, the exact $\beta$ values are not reproduced by PDR or shock models alone and a combination of both is needed. We find that the three major mergers among our targets have shallower temperature distributions for warm molecular gas than the other three spiral galaxies. This can be explained by a higher relative contribution of shock excitation, with respect to PDR excitation, for the warm molecular gas in these mergers. For only one of the mergers, IRASF 05189-2524, the shallower H2 temperature distribution differs from that of the spiral galaxies. The presence of a bright active galactic nucleus in this source might explain the warmer molecular gas observed.Comment: A&A in press; 15 pages, 7 figures. Fixed several typo

Star formation and nuclear activity of local luminous infrared galaxies

Tesis doctoral inédita. Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física Teórica. Fecha de lectura: 03-02-201

An X-ray Study of Local Infrared Bright Galaxies

We are carrying out detailed study of the X-ray and infrared (IR) properties of a sample of local (d < 70 Mpc) luminous infrared galaxies (LIRGs) using XMM-Newton and Spitzer (imaging and spectroscopy). The main goal is to study the extreme processes of star formation and/or active galactic nuclei (AGN) taking place in this cosmologically important class of galaxies. In this proceedings we present the preliminary results obtained from the analysis of the XMM-Newton X-ray images and the X-ray spectral modeling.Comment: 5 pages, to appear in Highlights of Spanish Astrophysics VI, Proceedings of the IX Scientific Meeting of the Spanish Astronomical Society held on September 13-17, 2010, in Madrid, Spai

Far-infrared line spectra of active galaxies from the Herschel/PACS Spectrometer: the complete database

We present a coherent database of spectroscopic observations of far-IR fine-structure lines from the Herschel/PACS archive for a sample of 170 local AGN, plus a comparison sample of 20 starburst galaxies and 43 dwarf galaxies. Published Spitzer/IRS and Herschel/SPIRE line fluxes are included to extend our database to the full 10-600 $\mu m$ spectral range. The observations are compared to a set of CLOUDY photoionisation models to estimate the above physical quantities through different diagnostic diagrams. We confirm the presence of a stratification of gas density in the emission regions of the galaxies, which increases with the ionisation potential of the emission lines. The new [OIV]25.9$\mu m$/[OIII]88$\mu m$ vs [NeIII]15.6$\mu m$/[NeII]12.8$\mu m$ diagram is proposed as the best diagnostic to separate: $i)$ AGN activity from any kind of star formation; and $ii)$ low-metallicity dwarf galaxies from starburst galaxies. Current stellar atmosphere models fail to reproduce the observed [OIV]25.9$\mu m$/[OIII]88$\mu m$ ratios, which are much higher when compared to the predicted values. Finally, the ([NeIII]15.6$\mu m$ + [NeII]12.8$\mu m$)/([SIV]10.5$\mu m$ + [SIII]18.7$\mu m$) ratio is proposed as a promising metallicity tracer to be used in obscured objects, where optical lines fail to accurately measure the metallicity. The diagnostic power of mid- to far-infrared spectroscopy shown here for local galaxies will be of crucial importance to study galaxy evolution during the dust-obscured phase at the peak of the star formation and black-hole accretion activity ($1 < z < 4$). This study will be addressed by future deep spectroscopic surveys with present and forthcoming facilities such as JWST, ALMA, and SPICA.Comment: Accepted for publication in the ApJ

Heating of the molecular gas in the massive outflow of the local ultraluminous-infrared and radio-loud galaxy 4C12.50

We present a comparison of the molecular gas properties in the outflow vs. in the ambient medium of the local prototype radio-loud and ultraluminous-infrared galaxy 4C12.50 (IRAS13451+1232), using new data from the IRAM Plateau de Bure interferometer and 30m telescope, and the Herschel space telescope. Previous H_2 (0-0) S(1) and S(2) observations with the Spitzer space telescope had indicated that the warm (~400K) molecular gas in 4C12.50 is made up of a 1.4(+-0.2)x10^8 M_sun ambient reservoir and a 5.2(+-1.7)x10^7 M_sun outflow. The new CO(1-0) data cube indicates that the corresponding cold (25K) H_2 gas mass is 1.0(+-0.1)x10^10 M_sun for the ambient medium and <1.3x10^8 M_sun for the outflow, when using a CO-intensity-to-H_2-mass conversion factor alpha of 0.8 M_sun /(K km/s pc^2). The combined mass outflow rate is high, 230-800 M_sun/yr, but the amount of gas that could escape the galaxy is low. A potential inflow of gas from a 3.3(+-0.3)x10^8 M_sun tidal tail could moderate any mass loss. The mass ratio of warm-to-cold molecular gas is >= 30 times higher in the outflow than in the ambient medium, indicating that a non-negligible fraction of the accelerated gas is heated to temperatures at which star formation is inefficient. This conclusion is robust against the use of different alpha factor values, and/or different warm gas tracers (H_2 vs. H_2 plus CO): with the CO-probed gas mass being at least 40 times lower at 400K than at 25K, the total warm-to-cold mass ratio is always lower in the ambient gas than in the entrained gas. Heating of the molecular gas could facilitate the detection of new outflows in distant galaxies by enhancing their emission in intermediate rotational number CO lines.Comment: A&A, in pres

Outflows of hot molecular gas in ultra-luminous infra-red galaxies mapped with VLT-SINFONI

We present the detection and morphological characterization of hot molecular gas outflows in nearby ultra-luminous infrared galaxies, using the near-IR integral-field spectrograph SINFONI on the VLT. We detect outflows observed in the 2.12 micron H$_{2}$ 1-0 S(1) line for three out of four ULIRGs analyzed; IRAS 12112+0305, 14348-1447, and 22491-1808. The outflows are mapped on scales of 0.7-1.6 kpc, show typical outflow velocities of 300-500 km/s, and appear to originate from the nuclear region. The outflows comprise hot molecular gas masses of ~6-8x10$^3$ M(sun). Assuming a hot-to-cold molecular gas mass ratio of 6x10$^{-5}$, as found in nearby luminous IR galaxies, the total (hot+cold) molecular gas mass in these outflows is expected to be ~1x10$^{8}$ M(sun). This translates into molecular mass outflow rates of ~30-85 M(sun)/yr, which is a factor of a few lower than the star formation rate in these ULIRGs. In addition, most of the outflowing molecular gas does not reach the escape velocity of these merger systems, which implies that the bulk of the outflowing molecular gas is re-distributed within the system and thus remains available for future star formation. The fastest H$_{2}$ outflow is seen in the Compton-thick AGN of IRAS 14348-1447, reaching a maximum outflow velocity of ~900 km/s. Another ULIRG, IRAS 17208-0014, shows asymmetric H$_{2}$ line profiles different from the outflows seen in the other three ULIRGs. We discuss several alternative explanations for its line asymmetries, including a very gentle galactic wind, internal gas dynamics, low-velocity gas outside the disk, or two superposed gas disks. We do not detect the hot molecular counterpart to the outflow previously detected in CO(2-1) in IRAS 17208-0014, but we note that our SINFONI data are not sensitive enough to detect this outflow if it has a small hot-to-cold molecular gas mass ratio of < 9x10$^{-6}$.Comment: Accepted for publication in A&A (11 pages, 10 figures

Local Luminous Infrared Galaxies. III. Co-evolution of Black Hole Growth and Star Formation Activity?

Local luminous infrared (IR) galaxies (LIRGs) have both high star formation rates (SFR) and a high AGN (Seyfert and AGN/starburst composite) incidence. Therefore, they are ideal candidates to explore the co-evolution of black hole (BH) growth and star formation (SF) activity, not necessarily associated with major mergers. Here, we use Spitzer/IRS spectroscopy of a complete volume-limited sample of local LIRGs (distances of <78Mpc). We estimate typical BH masses of 3x10^7 M_sun using [NeIII]15.56micron and optical [OIII]5007A gas velocity dispersions and literature stellar velocity dispersions. We find that in a large fraction of local LIRGs the current SFR is taking place not only in the inner nuclear ~1.5kpc region, as estimated from the nuclear 11.3micron PAH luminosities, but also in the host galaxy. We next use the ratios between the SFRs and BH accretion rates (BHAR) to study whether the SF activity and BH growth are contemporaneous in local LIRGs. On average, local LIRGs have SFR to BHAR ratios higher than those of optically selected Seyferts of similar AGN luminosities. However, the majority of the IR-bright galaxies in the RSA Seyfert sample behave like local LIRGs. Moreover, the AGN incidence tends to be higher in local LIRGs with the lowest SFRs. All this suggests that in local LIRGs there is a distinct IR-bright star forming phase taking place prior to the bulk of the current BH growth (i.e., AGN phase). The latter is reflected first as a composite and then as a Seyfert, and later as a non-LIRG optically identified Seyfert nucleus with moderate SF in its host galaxy.Comment: Accepted for publication in Ap