- ID:
- ivo://CDS.VizieR/J/ApJ/769/79
- Title:
- Spitzer observations of radio-loud AGNs (CARLA)
- Short Name:
- J/ApJ/769/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the first results from the Clusters Around Radio-Loud AGN program, a Cycle 7 and 8 Spitzer Space Telescope snapshot program to investigate the environments of a large sample of obscured and unobscured luminous radio-loud active galactic nuclei (AGNs) at 1.2<z<3.2. These data, obtained for 387 fields, reach 3.6 and 4.5{mu}m depths of [3.6]_AB_=22.6 and [4.5]_AB_=22.9 at the 95% completeness level, which is two to three times fainter than L* in this redshift range. By using the color cut [3.6]-[4.5]>-0.1 (AB), which efficiently selects high-redshift (z>1.3) galaxies of all types, we identify galaxy cluster member candidates in the fields of the radio-loud AGN. The local density of these Infrared Array Camera (IRAC)-selected sources is compared to the density of similarly selected sources in blank fields. We find that 92% of the radio-loud AGN reside in environments richer than average. The majority (55%) of the radio-loud AGN fields are found to be overdense at a>=2{sigma} level; 10% are overdense at a>=5{sigma} level. A clear rise in surface density of IRAC-selected sources toward the position of the radio-loud AGN strongly supports an association of the majority of the IRAC-selected sources with the radio-loud AGN. Our results provide solid statistical evidence that radio-loud AGN are likely beacons for finding high-redshift galaxy (proto-)clusters. We investigate how environment depends on AGN type (unobscured radio-loud quasars versus obscured radio galaxies), radio luminosity and redshift, finding no correlation with either AGN type or radio luminosity. We find a decrease in density with redshift, consistent with galaxy evolution for this uniform, flux-limited survey. These results are consistent with expectations from the orientation-driven AGN unification model, at least for the high radio luminosity regimes considered in this sample.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/717/1181
- Title:
- Spitzer power-law galaxies in EGS
- Short Name:
- J/ApJ/717/1181
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper analyzes a sample of 489 Spitzer/Infrared Array Camera (IRAC) sources in the Extended Groth Strip (EGS), whose spectral energy distributions fit a red power law (PL) from 3.6 to 8.0um. The median redshift for sources with known redshifts is <z>=1.6. Though all or nearly all of the sample galaxies are likely to be active galactic nuclei (AGNs), only 33% were detected in the EGS X-ray survey (AEGIS-X) using 200ks Chandra observations. The detected sources are X-ray luminous with L_X_>10^43^erg/s and moderately to heavily obscured with N_H_>10^22^cm^-2^. Stacking the X-ray-undetected sample members yields a statistically significant X-ray signal, suggesting that they are on average more distant or more obscured than sources with X-ray detections. The ratio of X-ray to mid-infrared fluxes suggests that a substantial fraction of the sources undetected in X-rays are obscured at the Compton-thick level, in contrast to the X-ray-detected sources, all of which appear to be Compton thin.
- ID:
- ivo://CDS.VizieR/J/ApJ/703/1778
- Title:
- Spitzer sources in SWIRE/XMM/ELAIS-S1 field
- Short Name:
- J/ApJ/703/1778
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of optical spectroscopic identifications of sources detected by Spitzer at 3.6 or 24um down to ~10 and ~280uJy, respectively, in the SWIRE/XMM-Newton/ELAIS-S1 field and classified via line width analysis and diagnostic diagrams. A total of 1376 sources down to R~24.2mag have been identified (1362 detected at 3.6um, 419 at 24um, and 405 at both) by low-resolution optical spectroscopy carried out with FORS2, VIMOS, and EFOSC2 at the Very Large Telescope and 3.6m ESO telescope. The spectroscopic campaigns have been carried out over the central 0.6deg^2^ area of ELAIS-S1 which, in particular, has also been observed by XMM-Newton and Chandra. We find the first direct optical spectroscopic evidence that the fraction of active galactic nuclei (AGNs; mostly AGN2) increases with increasing F(24um)/F(R) ratio, reaching values of 70(+/-20)% in the range 316<F(24um)/F(R)<1000. We present an Infrared Array Camera-Multiband Imaging Photometer color-color diagram able to separate AGN1 from obscured AGN2 candidates. After having corrected for the spectroscopic incompleteness of our sample, the result is that the AGN fraction at F(24um)~0.8mJy is ~22(+/-7)% and decreases slowly to ~19(+/-5)% down to F(24um)~0.3mJy.
- ID:
- ivo://CDS.VizieR/J/A+A/630/A153
- Title:
- Staked SEDs and templates of LBGs at z~3
- Short Name:
- J/A+A/630/A153
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore, from a statistical point of view, the rest-frame far-ultraviolet (FUV) to far-infrared (FIR) emission of a population of Lyman-break galaxies (LBGs) at z~3 that cannot be individually detected from current FIR observations. We performed a stacking analysis over a sample of ~17000 LBGs at redshift 2.5<z<3.5 in the COSMOS field. The sample is binned as a function of UV luminosity (L_FUV_), UV continuum slope (beta_UV_), and stellar mass (M*), and then stacked at optical (BVriz bands), near-infrared (YJHKs bands), IRAC (3.6, 4.5, 5.6 and 8.0um), MIPS (24um), PACS (100 and 160 um), SPIRE (250, 350, and 500um), and AzTEC (1.1mm) observations. We obtained 30 rest-frame FUV-to-FIR spectral energy distributions (SEDs) of LBGs at z~3, and analyzed these with the CIGALE SED-fitting analysis code. We were able to derive fully consistent physical parameters, that is, M*, beta_UV_, L_FUV_, L_IR_, A_FUV_, star formation rate, and the slope of the dust attenuation law; we built a semiempirical library of 30 rest-frame FUV-to-FIR stacked LBG SEDs as functions of L_FUV_, beta_UV_, and M*. Additionally, We used the so-called IR-excess (IRX) to investigate the dust attenuation and the shape of the dust attenuation curve as a function of L_UV_, beta_UV_ and M*.
- ID:
- ivo://CDS.VizieR/J/A+A/629/A6
- Title:
- 3 starburst galaxies 12C/13C ALMA datacubes
- Short Name:
- J/A+A/629/A6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive molecular-gas-phase ^12^C/^13^C isotope ratios for the central few hundred parsecs of the three nearby starburst galaxies NGC253, NGC1068, and NGC4945 making use of the {lambda}~3mm ^12^CN and ^13^CN N=1-0 lines in the ALMA Band 3. The ^12^C/^13^C isotopic ratios derived from the ratios of these lines range from 30 to 67 with an average of 41.6+/-0.2 in NGC253, from 24 to 62 with an average of 38.3+/-0.4 in NGC1068, and from 6 to 44 with an average of 16.9+/-0.3 in NGC4945. The highest ^12^C/^13^C isotopic ratios are determined in some of the outskirts of the nuclear regions of the three starburst galaxies. The lowest ratios are associated with the northeastern and southwestern molecular peaks of NGC253, the northeastern and southwestern edge of the mapped region in NGC1068, and the very center of NGC4945. In the case of NGC 1068, the measured ratios suggest inflow from the outer part of NGC1068 into the circum-nuclear disk through both the halo and the bar. Low ^12^C/^13^C isotopic ratios in the central regions of these starburst galaxies indicate the presence of highly processed material.
- ID:
- ivo://CDS.VizieR/J/AJ/150/43
- Title:
- Star formation in active and normal galaxies
- Short Name:
- J/AJ/150/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigated the properties of the host galaxies of active galactic nuclei (AGNs). We used radio emission around the nuclei of the host galaxies to represent AGN activity and used infrared (IR) emission to represent the star-forming activity and stellar population of the host galaxies. We determined that active galaxies have higher stellar masses (SMs) within the central kiloparsec radius than normal galaxies do independent of the Hubble types of the host galaxies; but both active and normal galaxies exhibit similar specific star formation rates (SSFRs), ranging between 10^-10.5^ and 10^-9.5^/yr. We find that the central SM surface density might be used as an indicator to identify AGNs. We also discovered that certain AGNs exhibit substantial inner stellar structures in the IR images; most of the AGNs with inner structures are Seyferts, whereas only a few LINERs exhibit inner structures. We note that the AGNs with inner structures show a positive correlation between the radio activity of the AGNs and the SFRs of the host galaxies, but the sources without inner structures show a negative correlation between the radio power and the SFRs. These results might be explained with a scenario of starburst-AGN evolution. In this scenario, AGN activities are triggered following a nuclear starburst; during the evolution, AGN activities are accompanied by SF activity in the inner regions of the host galaxies; at the final stage of the evolution, the AGNs might transform into LINERs, exhibiting weak SF activity in the central regions of the host galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/288/713
- Title:
- Star formation in galaxies
- Short Name:
- J/A+A/288/713
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Evolutionary models of disk galaxies are presented (table3), and are confronted with a sample of late type galaxies from the Tully (Nearby Galaxies, see Cat. <VII/145>) and the de Vaucouleurs (RC3, see Cat. <VII/155>) catalogues.
- ID:
- ivo://CDS.VizieR/J/ApJ/761/97
- Title:
- Star Formation in Radio Survey (SFRS): 33GHz obs.
- Short Name:
- J/ApJ/761/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 33GHz photometry of 103 galaxy nuclei and extranuclear star-forming complexes taken with the Green Bank Telescope (GBT) as part of the Star Formation in Radio Survey (SFRS). Among the sources without evidence for an active galactic nucleus, and also having lower frequency radio data, we find a median thermal fraction at 33GHz of {approx}76% with a dispersion of {approx}24%. For all sources resolved on scales <~0.5kpc, the thermal fraction is even larger, being >~90%. This suggests that the rest-frame 33GHz emission provides a sensitive measure of the ionizing photon rate from young star-forming regions, thus making it a robust star formation rate (SFR) indicator. Taking the 33 GHz SFRs as a reference, we investigate other empirical calibrations relying on different combinations of warm 24{mu}m dust, total infrared (IR; 8-1000{mu}m), H{alpha} line, and far-UV continuum emission. The recipes derived here generally agree with others found in the literature, albeit with a large dispersion that most likely stems from a combination of effects. Comparing the 33GHz to total IR flux ratios as a function of the radio spectral index, measured between 1.7 and 33GHz, we find that the ratio increases as the radio spectral index flattens which does not appear to be a distance effect. Consequently, the ratio of non-thermal to total IR emission appears relatively constant, suggesting only moderate variations in the cosmic-ray electron injection spectrum and ratio of synchrotron to total cooling processes among star-forming complexes. Assuming that this trend solely arises from an increase in the thermal fraction sets a maximum on the scatter of the non-thermal spectral indices among the star-forming regions of {sigma}_{alpha}_NT<~0.13.
- ID:
- ivo://CDS.VizieR/J/ApJ/619/L95
- Title:
- Star formation in Stephan's Quintet
- Short Name:
- J/ApJ/619/L95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first Galaxy Evolution Explorer (GALEX) UV images of the well-known interacting group of galaxies, Stephan's Quintet (SQ). We detect widespread UV emission throughout the group. However, there is no consistent coincidence between UV structure and emission in the optical, H{alpha}, or HI. Excluding the foreground galaxy NGC 7320 (Sd), most of the UV emission is found in regions associated with the two spiral members of the group, NGC 7319 and NGC 7318b, and the intragroup medium starburst SQ-A. The extinction-corrected UV data are analyzed to investigate the overall star formation activity in SQ.
- ID:
- ivo://CDS.VizieR/J/ApJ/688/1142
- Title:
- Star formation in W5: Spitzer observations
- Short Name:
- J/ApJ/688/1142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present images and initial results from our extensive Spitzer Space Telescope imaging survey of the W5 HII region with the Infrared Array Camera (IRAC) and Multiband Imaging Photometer for Spitzer (MIPS). We detect dense clusters of stars, centered on the O stars HD 18326, BD +60 586, HD 17505, and HD 17520. At 24um, substantial extended emission is visible, presumably from heated dust grains that survive in the strongly ionizing environment of the HII region. With photometry of more than 18000 point sources, we analyze the clustering properties of objects classified as young stars by their IR spectral energy distributions (a total of 2064 sources) across the region using a minimal-spanning-tree algorithm. We find ~40%-70% of infrared excess sources belong to clusters with >=10 members. We find that within the evacuated cavities of the HII regions that make up W5, the ratio of Class II to Class I sources is ~7 times higher than for objects coincident with molecular gas as traced by ^12^CO emission and near-IR extinction maps. We attribute this contrast to an age difference between the two locations and postulate that at least two distinct generations of star formation are visible across W5. Our preliminary analysis shows that triggering is a plausible mechanism to explain the multiple generations of star formation in W5 and merits further investigation.
