scholarly journals Anomalous Hydrogen Recombination Line Ratios in Ultraluminous Infrared Galaxies

2021 ◽  
Vol 922 (2) ◽  
pp. 272
Author(s):  
Kenichi Yano ◽  
Shunsuke Baba ◽  
Takao Nakagawa ◽  
Matthew A. Malkan ◽  
Naoki Isobe ◽  
...  
Keyword(s):  
Column Density ◽  
High Density ◽  
Line Ratio ◽  
Infrared Galaxies ◽  
Recombination Line ◽  
Gas Density ◽  
Dust Extinction ◽  
Hydrogen Recombination ◽  
Ultraluminous Infrared Galaxies

Abstract We conducted systematic observations of the H i Brα (4.05 μm) and Brβ (2.63 μm) lines in 52 nearby (z < 0.3) ultraluminous infrared galaxies (ULIRGs) with AKARI. Among 33 ULIRGs wherein the lines are detected, 3 galaxies show anomalous Brβ/Brα line ratios (∼1.0), which are significantly higher than those for case B (0.565). Our observations also show that ULIRGs have a tendency to exhibit higher Brβ/Brα line ratios than those observed in Galactic H ii regions. The high Brβ/Brα line ratios cannot be explained by a combination of dust extinction and case B since dust extinction reduces the ratio. We explore possible causes for the high Brβ/Brα line ratios and show that the observed ratios can be explained by a combination of an optically thick Brα line and an optically thin Brβ line. We simulated the H ii regions in ULIRGs with the Cloudy code, and our results show that the high Brβ/Brα line ratios can be explained by high-density conditions, wherein the Brα line becomes optically thick. To achieve a column density large enough to make the Brα line optically thick within a single H ii region, the gas density must be as high as n ∼ 108 cm−3. We therefore propose an ensemble of H ii regions, in each of which the Brα line is optically thick, to explain the high Brβ/Brα line ratio.

Early science with the LMT: molecular torus in UGC 5101

2020 ◽  
Vol 499 (2) ◽  
pp. 2042-2050
Author(s):  
I Cruz-González ◽  
A I Gómez-Ruiz ◽  
A Caldú-Primo ◽  
E Benítez ◽  
J M Rodríguez-Espinosa ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Rotational Velocity ◽  
Galactic Nuclei ◽  
High Density ◽  
Infrared Galaxies ◽  
X Ray ◽  
Ultraluminous Infrared Galaxies ◽  
Molecular Lines ◽  
Frequency Window ◽  
Integrated Intensities

ABSTRACT As part of the Early Science Large Millimeter Telescope projects, we report the detection of nine double-peaked molecular lines, produced by a rotating molecular torus, in the ultraluminous infrared galaxies (ULIRG) – Compton-thick active galactic nuclei (AGN) galaxy UGC 5101. The double-peaked lines we report correspond to molecular transitions of HCN, HCO+, HNC, N2H+, CS, C18O, 13CO, and two CN lines; plus the detection of C2H that is a blend of six lines. The redshift search receiver spectra covers the 73–113 GHz frequency window. Low- and high-density gas tracers of the torus have different implied rotational velocities, with a rotational velocity of 149 ± 3  km s−1 for the low-density ones (C18O, 13CO) and 174 ± 3  km s−1 for high-density tracers (HCN, HCO+, HNC, N2H+, CS, and CN). In UGC 5101, we find that the ratio of integrated intensities of HCN to 13CO to be unusually large, probably indicating that the gas in the torus is very dense. Both the column densities and abundances are consistent with values found in AGN, starburst, and ULIRG galaxies. The observed abundance ratios cannot discriminate between X-ray and UV-field-dominated regions.

scholarly journals Deciphering an evolutionary sequence of merger stages in infrared-luminous starburst galaxies atz∼ 0.7

2019 ◽  
Vol 623 ◽  
pp. A64 ◽  
Author(s):  
A. Calabrò ◽  
E. Daddi ◽  
A. Puglisi ◽  
E. Oliva ◽  
R. Gobat ◽  
...  
Keyword(s):  
Elliptical Galaxies ◽  
Starburst Galaxies ◽  
Good Time ◽  
Evolutionary Sequence ◽  
Infrared Galaxies ◽  
Potential Wells ◽  
Near Ir ◽  
Hydrogen Recombination ◽  
Ultraluminous Infrared Galaxies ◽  
Parameter Sequence

Based on optical and near-IRMagellanFIRE spectra of 25 starburst galaxies at 0.5 <  z <  0.9, a recent publication showed that their attenuation properties can be explained by a single-parameter sequence of total obscurations ranging fromAV = 2 toAV = 30 toward the starburst core centers in a mixed stars and dust configuration. We investigate here the origin of this sequence for the same sample. We show that total attenuations anticorrelate with the starburst sizes in radio (3 GHz) with a significance larger than 5σand a scatter of 0.26 dex. More obscured and compact starbursts also show enhanced N2 (=[NII]/Hα) ratios and larger line velocity widths that we attribute to an increasing shock contribution toward later merger phases, driven by deeper gravitational potential wells at the coalescence. Additionally, the attenuation is also linked to the equivalent width (EW) of hydrogen recombination lines, which is sensitive to the luminosity weighted age of the relatively unobscured stellar populations. Overall, the correlations amongAV, tot, radio size, line width, N2 and EW of Balmer and Paschen lines converge toward suggesting an evolutionary sequence of merger stages: all of these quantities are likely to be good time-tracers of the merger phenomenon, and their large spanned range appears to be characteristic of the different merger phases. Half of our sample at higher obscurations have radio sizes approximately 3 times smaller than early type galaxies at the same redshift, suggesting that, in analogy with local ultraluminous infrared galaxies (ULIRGs), these cores cannot be directly forming elliptical galaxies. Finally, we detect mid-IR AGN torus for half of our sample and additional X-ray emission for 6 starbursts; intriguingly, the latter have systematically more compact sizes, suggestive of emerging AGNs toward later merger stages, possibly precursors of a later QSO phase.

scholarly journals The AKARI 2.5–5 micron spectra of luminous infrared galaxies in the local Universe

2018 ◽  
Vol 617 ◽  
pp. A130 ◽  
Author(s):  
H. Inami ◽  
L. Armus ◽  
H. Matsuhara ◽  
V. Charmandaris ◽  
T. Díaz-Santos ◽  
...  
Keyword(s):  
Continuum Emission ◽  
Absorption Feature ◽  
Infrared Galaxies ◽  
Mid Infrared ◽  
Dust Extinction ◽  
Luminous Infrared Galaxies ◽  
Hydrogen Recombination ◽  
Diagnostic Diagram ◽  
High Ionization ◽  
Polycyclic Aromatic

We present AKARI 2.5–5 μm spectra of 145 local luminous infrared galaxies (LIRG; LIR ≥ 1011 L⊙) in the Great Observatories All-sky LIRG Survey (GOALS). In all of the spectra, we measure the line fluxes and equivalent widths (EQWs) of the polycyclic aromatic hydrocarbon (PAH) at 3.3 μm and the hydrogen recombination line Brα at 4.05 μm, with apertures matched to the slit sizes of the Spitzer low-resolution spectrograph and with an aperture covering ∼95% of the total flux in the AKARI two-dimensional (2D) spectra. The star formation rates (SFRs) derived from the Brα emission measured in the latter aperture agree well with SFRs estimated from LIR, when the dust extinction correction is adopted based on the 9.7 μm silicate absorption feature. Together with the Spitzer Infrared Spectrograph (IRS) 5.2–38 μm spectra, we are able to compare the emission of the PAH features detected at 3.3 μm and 6.2 μm. These are the two most commonly used near/mid-infrared indicators of starburst or active galactic nucleus (AGN) dominated galaxies. We find that the 3.3 μm and 6.2 μm PAH EQWs do not follow a linear correlation and at least a third of the galaxies classified as AGN-dominated sources using the 3.3 μm feature are classified as starbursts based on the 6.2 μm feature. These galaxies have a bluer continuum slope than galaxies that are indicated to be starburst-dominated by both PAH features. The bluer continuum emission suggests that their continuum is dominated by stellar emission rather than hot dust. We also find that the median Spitzer/IRS spectra of these sources are remarkably similar to the pure starburst-dominated sources indicated by high PAH EQWs in both 3.3 μm and 6.2 μm. Based on these results, we propose a revised starburst/AGN diagnostic diagram using 2–5 μm data: the 3.3 μm PAH EQW and the continuum color, Fν(4.3 μm)/Fν(2.8 μm). We use the AKARI and Spitzer spectra to examine the performance of our new starburst/AGN diagnostics and to estimate 3.3 μm PAH fluxes using the James Webb Space Telescope (JWST) photometric bands in the redshift range 0 < z < 5. Of the known PAH features and mid-infrared high ionization emission lines used as starburst/AGN indicators, only the 3.3 μm PAH feature is observable with JWST at z > 3.5, because the rest of the features at longer wavelengths fall outside the JWST wavelength coverage.

scholarly journals A New MIR/submm Diagnostic for Dust-Enshrouded AGN

2002 ◽  
Vol 184 ◽  
pp. 205-212
Author(s):  
Martin Haas
Keyword(s):  
Flux Ratio ◽  
Peak Height ◽  
Dust Grains ◽  
Infrared Galaxies ◽  
Mid Infrared ◽  
Dust Extinction ◽  
Ultraluminous Infrared Galaxies ◽  
Polycyclic Aromatic ◽  
Dust Distribution ◽  
Infrared Extinction

AbstractWe show that the PAH 7.7μm to continuum 850μm flux ratio can be used to reveal high mid-infrared extinction in ultraluminous infrared galaxies (ULIRGs). While the submm radiation is optically thin and represents the emission from essentially all dust grains, the PAH strength (measured by the peak height of the Polycyclic Aromatic Hydocarbonates at 7.7μm) is sensitive to dust extinction in the mid-infrared (MIR). As an application of the new diagnostic, after dereddening of the central MIR continuum and with the assumption of a disk-like dust distribution seen under a tilted angle, we find increasing evidence for a hidden quasar in the archetypal ULIRG Arp220.

scholarly journals Dynamical Properties of Ultraluminous Infrared Galaxies. II. Traces of Dynamical Evolution and End Products of Local Ultraluminous Mergers

2006 ◽  
Vol 651 (2) ◽  
pp. 835-852 ◽  
Author(s):  
K. M. Dasyra ◽  
L. J. Tacconi ◽  
R. I. Davies ◽  
T. Naab ◽  
R. Genzel ◽  
...  
Keyword(s):  
Dynamical Evolution ◽  
Infrared Galaxies ◽  
End Products ◽  
Ultraluminous Infrared Galaxies ◽  
Dynamical Properties

scholarly journals Dynamical Properties of Ultraluminous Infrared Galaxies. I. Mass Ratio Conditions for ULIRG Activity in Interacting Pairs

2006 ◽  
Vol 638 (2) ◽  
pp. 745-758 ◽  
Author(s):  
K. M. Dasyra ◽  
L. J. Tacconi ◽  
R. I. Davies ◽  
R. Genzel ◽  
D. Lutz ◽  
...  
Keyword(s):  
Mass Ratio ◽  
Infrared Galaxies ◽  
Ultraluminous Infrared Galaxies ◽  
Dynamical Properties

scholarly journals Follow-up near-infrared spectroscopy of ultraluminous infrared galaxies observed by ISO

2005 ◽  
Vol 441 (3) ◽  
pp. 999-1010 ◽  
Author(s):  
H. Dannerbauer ◽  
D. Rigopoulou ◽  
D. Lutz ◽  
R. Genzel ◽  
E. Sturm ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
Near Infrared Spectroscopy ◽  
Near Infrared ◽  
Infrared Galaxies ◽  
Ultraluminous Infrared Galaxies

scholarly journals Dark dust and single-cloud sightlines in the ISM

2020 ◽  
Vol 641 ◽  
pp. A35
Author(s):  
R. Siebenmorgen ◽  
J. Krełowski ◽  
J. Smoker ◽  
G. Galazutdinov ◽  
S. Bagnulo
Keyword(s):  
Interstellar Medium ◽  
Spectral Type ◽  
Column Density ◽  
Resolving Power ◽  
High Resolution Spectroscopy ◽  
Luminosity Distance ◽  
Ob Stars ◽  
Dust Extinction ◽  
Heating Source ◽  
Dust Component

The precise characteristics of clouds and the nature of dust in the diffuse interstellar medium can only be extracted by inspecting the rare cases of single-cloud sightlines. In our nomenclature such objects are identified by interstellar lines, such as K I, that show at a resolving power of λ∕Δλ ~ 75 000 one dominating Doppler component that accounts for more than half of the observed column density. We searched for such sightlines using high-resolution spectroscopy towards reddened OB stars for which far-UV extinction curves are known. We compiled a sample of 186 spectra, 100 of which were obtained specifically for this project with UVES. In our sample we identified 65 single-cloud sightlines, about half of which were previously unknown. We used the CH/CH+ line ratio of our targets to establish whether the sightlines are dominated by warm or cold clouds. We found that CN is detected in all cold (CH/CH+ > 1) clouds, but is frequently absent in warm clouds. We inspected the WISE (3−22 μm) observed emission morphology around our sightlines and excluded a circumstellar nature for the observed dust extinction. We found that most sightlines are dominated by cold clouds that are located far away from the heating source. For 132 stars, we derived the spectral type and the associated spectral type-luminosity distance. We also applied the interstellar Ca II distance scale, and compared these two distance estimates with Gaia parallaxes. These distance estimates scatter by ~40%. By comparing spectral type-luminosity distances with those of Gaia, we detected a hidden dust component that amounts to a few mag of extinction for eight sightlines. This dark dust is populated by ≳ 1 μm large grains and predominately appears in the field of the cold interstellar medium.

Sign in / Sign up

Export Citation Format

Share Document