The ISO-2MASS AGN survey: on the type-1 sources

Leipski, C.; Haas, Martín; Meusinger, H.; Siebenmorgen, R.; Chini, R.; Scheyda, C. M.; Albrecht, M.; Wilkes, B. J.; Huchra, J. P.; Ott, Stephan; Césarsky, C. J.; Cutri, R. M.

doi:10.1051/0004-6361:200500152

Cited by 23 publications

(25 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In view of the clearly reddish and obscured character of the 2MASX J20183871+4041003 source, we conclude that it might belong to the class of so-called red post-starburst QSOs. They are believed to comprise between 10% and 20% of all QSOs according to different surveys (Leipski et al 2005;Roseboom et al 2006), which is consistent with the co-evolution of galaxy mergers, quasars, and the blue/red galaxy transitions (Hopkins et al 2006b). We further point out that to finally derive the spectroscopical redshift of B2013+370, one will need an exposure on the order of 4500 s on the VLT class telescope equipped with a focal instrument like FORS2 to get a sufficiently good spectrum of the object with a signal-to-noise ratio of ∼20.…”

Section: Discussionsupporting

confidence: 66%

Gamma-ray absorption method (GRAM) application to the identification of EGRET unidentified sources

Iyudin

Burwitz

Greiner

et al. 2007

A&A

View full text Add to dashboard Cite

Recently we reported the very first detection of γ-ray resonant absorption along the line of sight toward γ-ray bright quasars (QSOs) like 3C 273, 3C 279, PKS 0528+0134, and BL Lacertae. These detections resulted from the analysis of absorption troughs in SEDs derived on the base of mostly EGRET data that were collected during monitoring campaigns of the Virgo and galactic anticenter regions by the Compton Gamma Ray Observatory (CGRO), as well as during ToO observations of QSOs flares. Among three resonant absorption mechanisms that affect the γ-ray spectrum of point-like sources, we now pinpoint the ∆-isobar resonance that has a very stable peak energy of the absorption cross-section for all elements (nuclei) and for individual nucleons. From two absorbers that are usually detected on the sight lines towards γ-ray bright QSOs, we concentrate here on the only one that is at the QSO rest frame. We discuss the advantages and drawbacks of this method distinguishing between a galactic and extragalactic origin of the EGRET unidentified sources (EUIDs). This is compared to the multiwavelength identification approach that was succesfully used in a few cases to identify galactic and extragalactic objects among EUIDs. We applied the GRAM to identifying two of the EGRET unidentified sources as blazars, and predict their respective redshifts.

show abstract

Section: Discussionsupporting

confidence: 66%

Gamma-ray absorption method (GRAM) application to the identification of EGRET unidentified sources

Iyudin

Burwitz

Greiner

et al. 2007

A&A

View full text Add to dashboard Cite

show abstract

“…Alonso-Herrero et al 2006), and as a combination of 24 µm and radio data (Martinez-Sansigre et al 2005;Weedman et al 2006), we have utilised the ISO-2MASS AGN survey. The results on the 24 type 1 AGN have been presented by Leipski et al (2005). Here, we report about the nine type 2 AGN.…”

Section: Introductionmentioning

confidence: 83%

Narrow-line AGN in the ISO-2MASS survey

Leipski¹,

Haas²,

Meusinger

et al. 2007

A&A

Self Cite

View full text Add to dashboard Cite

Context. A long-standing challenge of observational AGN research is to find type 2 quasars, the luminous analogues of Seyfert-2 galaxies. Aims. We search for luminous narrow-line type 2 AGN, characterise their properties, and compare them with broad-line type 1 AGN. Methods. Combining the ISOCAM parallel survey at 6.7 µm with 2MASS, we have selected AGN via near-mid-infrared colours caused by the hot nuclear dust emission. We performed spectroscopy in the optical and, for a subset of the sample, also in the midinfrared with Spitzer.Results. We find nine type 2 AGN at redshift 0.1 < z < 0.5, three of them have even quasar-like [O iii] luminosities. At the given redshift and luminosity range the number of type 2 AGN is at least as high as that of type 1s. At z > 0.5 we did not find type 2 AGN, probably because the hottest dust emission, still covered by the NIR filters, is obscured. The optical spectra of the type 2 host galaxies show young and old stellar populations. Only one object is an ultraluminous infrared galaxy with starburst. The 5-38 µm spectra of the two type 2 sources observed show a strong continuum with PAH emission in one case and silicate absorption in the other case. Conclusions. The near-mid-infrared selection is a successful strategy to find luminous type 2 AGN at low z. The objects exhibit a large range of properties so that it is difficult to infer details by means of popular SED fitting with simple average templates.

show abstract

“…While this range overlaps with that of the PAH-candidates, in this paper all sources with AGN signatures in their optical spectra are omitted. The results on the 33 ISO-2MASS-AGN have been presented by Leipski et al (2005.…”

Section: Near-mid-infrared Colour Selectionmentioning

confidence: 99%

Polycyclic aromatic hydrocarbon selected galaxies

Haas

Leipski

Siebenmorgen

et al. 2009

A&A

Self Cite

View full text Add to dashboard Cite

Context. This is the fourth in a series of papers based on the ISOCAM Parallel Survey at 6.7 μm. While the first three papers have been devoted to active galactic nuclei (AGN), here we report on emission-line galaxies without AGN signatures in their optical spectra. Aims. Polycyclic aromatic hydrocarbon (PAH) emission has been found in both starbursts and modestly starforming galaxies, but the relation between starforming activity and PAH luminosity is still a matter of debate. The different correlation degrees could be caused by the variety of optical and far-infrared sample selection criteria. In order to obtain a census of the typical properties of PAH emitting galaxies, we here study moderately distant galaxies which have been selected by their PAH emission. Methods. Combining the ISOCAM Parallel Survey at 6.7 μm with 2MASS we have colour-selected a sample of 120 candidates for strong PAH emission. We obtained optical and mid-infrared spectra of 75 and 19 sources, respectively, and analysed IRASADDSCANs and available Spitzer 3.6-160 μm photometry. Results. The Spitzer mid-infrared spectra exhibit clear PAH features and corroborate that our photometric selection criteria trace the PAH emission of galaxies fairly well. The optical spectra show emission lines, at median redshift z ∼ 0.1, as well as H δ and Ca II absorption, indicating ongoing starformation as well as post-starbursts. The mid-and far-infrared spectral energy distributions (SEDs) provide evidence for a broad range of far-infrared (FIR) luminosities (10 9 L −2 × 10 12 L ), but in general the dust is colder (T < ∼ 25 K, β = 2) than for starburst galaxies like M 82 (T ≈ 40 K). For most galaxies the monocromatic luminosity (ν · L ν ) peaks at about equal height at optical, 6.7 μm (PAH) and FIR wavelengths. In about 15% of the sources the FIR luminosity exceeds the optical and PAH energy output by about a factor 5-10 despite the cool dust temperature; in these galaxies a large dust mass of 10 8 -10 9 M is inferred. Conclusions. At moderate distance (z ∼ 0.1), PAH selected galaxies turn out to be a quite heterogeneous population of dust-rich, partly infrared-luminous galaxies but mostly cool with a range of post-starburst signatures and starforming activity which appears to be rather modest relative to the entire gas content (derived from the dust mass and assuming a standard gas/dust ratio). Our results on PAH selected galaxies question the often expressed interpretation that the majority of high redshift galaxies detected in 15 and 24 μm surveys are dominated by powerful ongoing starbursts with high starforming efficiency.

show abstract

The ISO-2MASS AGN survey: on the type-1 sources

Cited by 23 publications

References 18 publications

Gamma-ray absorption method (GRAM) application to the identification of EGRET unidentified sources

Gamma-ray absorption method (GRAM) application to the identification of EGRET unidentified sources

Narrow-line AGN in the ISO-2MASS survey

Polycyclic aromatic hydrocarbon selected galaxies

Contact Info

Product

Resources

About