Parent Sample Publications
A low-luminosity type-1 QSO sample IV - Molecular gas contents and conditions of star formation in three nearby Seyfert galaxies
We present a pilot study of ~3'' resolution observations of low CO transitions with the Submillimeter Array in three nearby Seyfert galaxies, which are part of the low-luminosity quasi-stellar object (LLQSOs) sample consisting of 99 nearby (z = 0.06) type-1 active galactic nuclei (AGN) taken from the Hamburg/ESO quasi-stellar object (QSO) survey. Two sources were observed in 12CO(2-1) and 13CO(2-1) and the third in 12CO(3-2) and HCO+(4-3). None of the sources is detected in continuum emission. More than 80% of the 12CO detected molecular gas is concentrated within a diameter (FWHM) < 1.8 kpc. 13CO is tentatively detected, while HCO+ emission could not be detected. All three objects show indications of a kinematically decoupled central unresolved molecular gas component. The molecular gas masses of the three galaxies are in the range Mmol = (0.7-8.7) × 109M⊙. We give lower limits for the dynamical masses of Mdyn> 1.5 × 109M⊙ and for the dust masses of Mdust> 1.6 × 106M⊙. The R21 = 12CO/13CO(2-1) line luminosity ratios show Galactic values of R21 ~ 5-7 in the outskirts and R21 ≳ 20 in the central region, similar to starbursts and (ultra)luminous infrared galaxies ((U)LIRGs; i.e. LIRGs and ULIRGs), implying higher temperatures and stronger turbulence. All three sources show indications of 12CO(2-1)/12CO(1-0) ratios of ~0.5, suggesting a cold or diffuse gas phase. Strikingly, the 12CO(3-2)/(1-0) ratio of ~1 also indicates a higher excited phase. Since these galaxies have high infrared luminosities of LIR ≥ 1011L⊙ and seem to contain a circumnuclear starburst with minimum surface densities of gas and star formation rate (SFR) around Σmol = 50-550 M⊙pc-2 and ΣSFR = 1.1-3.1 M⊙ kpc-2 yr-1, we conclude that the interstellar medium in the centers of these LIRG Seyferts is strongly affected by violent star formation and better described by the ULIRG mass conversion factor.
A low-luminosity type-1 QSO sample. V - Overluminous host spheroids and their excitation mechanisms
We present near-infrared (NIR) H + K-band long-slit spectra of eleven galaxies that were obtained with SOFI at the NTT (ESO). The galaxies are chosen from the low-luminosity type-1 quasi-stellar object (LLQSO) sample, which comprises the 99 closest (z ≤ 0.06) QSOs from the Hamburg/ESO survey for bright UV-excess QSOs. These objects are ideal targets to study the gap between local Seyfert galaxies and high-redshift quasars because they show much stronger AGN activity than local objects, but are still close enough for a detailed structural analysis. We fit hydrogen recombination, molecular hydrogen, and [Fe ii] lines after carefully subtracting the continuum emission. From the broad Paα components, we estimated black hole masses and enlarged the sample of LLQSOs that deviate from the MBH - Lbulge relations of inactive galaxies from 12 to 16 objects. All objects show emission from hot dust (T ~ 1200 K) as well as stellar contribution. However, the respective fractions vary strongly among the objects. More than half of the objects show H2 emission lines, which indicate a large reservoir of molecular gas that is needed to feed the AGN and star formation. In the NIR diagnostic diagram all objects lie in the location of AGN-dominated objects. However, most of the objects show indications of star formation activity, suggesting that their offset location with respect to MBH-Lbulge relations of inactive galaxies may be a consequence of overluminous bulges.
A low-luminosity type-1 QSO sample. I. Overluminous host spheroidals or undermassive black holes
Deep NIR J/H/K band imaging for a sample of 20 QSO host galaxies is presented in this paper from the parent sample of CARS. A QSO-host image decomposition was done to measure the mass of the bulge component of the host. This is compared to the BH mass inferred from longslit spectroscopy to probe the BH mass-bulge mass relation. The authors found that most of the bulge are below the local BH mass-bulge mass relation established for inactive galaxies.
A low-luminosity type-1 QSO sample: II. Tracing circumnuclear star formation in HE1029-1831 with SINFONI
The paper presents high spatial resolution NIR H+K band IFU observations of the central regions of HE1029-1401 which is also part of the CARS sample and observed with MUSE.
HI in nearby low-luminosity QSO host galaxies
This paper present HI observations for the majority of CARS galaxies with the 100m Effelsberg single-dish radio telescope. 12 QSO host galaxies have been detected in HI and upper limits are presented for the remaining 15 targets.
Molecular gas in nearby low-luminosity QSO host galaxies
This paper reports the CO(1-0) and CO(2-1) for a sample of QSO selected from the Hamburg ESO survey at 0.01<z<0.06 to probe their molecular gas content. It represent the basis for the CARS sample.
A low-luminosity type-1 QSO sample. III - Optical spectroscopic properties and activity classification
Context. We report on the optical spectroscopic analysis of a sample of 99 low-luminosity quasi-stellar objects (LLQSOs) at z ≤ 0.06 base the Hamburg/ESO QSO Survey (HES). To better relate the low-redshift active galactic nucleus (AGN) to the QSO population it is important to study samples of the latter type at a level of detail similar to that of the low-redshift AGN. Powerful QSOs, however, are absent at low redshifts due to evolutionary effects and their small space density. Our understanding of the (distant) QSO population is, therefore, significantly limited by angular resolution and sensitivity. The LLQSOs presented here offer the possibility of studying the faint end of this population at smaller cosmological distances and, therefore, in greater detail.Aims: In comparing two spectroscopic methods, we aim to establish a reliable activity classification scheme of the LLQSOs sample. Our goal is to enrich our systematic multiwavelength analysis of the AGN/starburst relation in these systems and give a complementary information on this particular sample of LLQSOs from the Hamburg ESO survey.Methods: Here, we present results of the analysis of visible wavelength spectroscopy provided by the HES and the 6 Degree Field Galaxy Survey (6dFGS). These surveys use different spectroscopic techniques, long-slit and circular fiber, respectively. These allow us to assess the influence of different apertures on the activity of the LLQSOs using classical optical diagnostic diagrams. We perform a Gaussian fitting of strong optical emission lines and decompose narrow and broad Balmer components.Results: A small number of our LLQSO present no broad component, which is likely to be present but buried in the noise. Two sources show double broad components, whereas six comply with the classic NLS1 requiremnts. As expected in NLR of broad line AGNs, the [Sii]-based electron density values range between 100 and 1000 Ne/cm3. Using the optical characteristics of Populations A and B, we find that 50% of our sources with Hβ broad emission are consistent with the radio-quiet sources definition. The remaining sources could be interpreted as low-luminosity radio-loud quasar. The BPT-based classification renders an AGN/Seyfert activity between 50 to 60%. For the remaining sources, the possible starburst contribution might control the LINER and Hii classification. Finally, we discuss the aperture effect as responsible for the differences found between data sets, although variability in the BLR could play a significant role as well.