- ID:
- ivo://CDS.VizieR/J/ApJS/217/11
- Title:
- HeI* in broad absorption line QSOs
- Short Name:
- J/ApJS/217/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Neutral helium multiplets, HeI*{lambda}{lambda}3189, 3889, 10830, are very useful diagnostics for the geometry and physical conditions of the absorbing gas in quasars. So far only a handful of HeI* detections have been reported. Using a newly developed method, we detected the HeI*{lambda}3889 absorption line in 101 sources of a well-defined sample of 285 MgII broad absorption line (BAL) quasars selected from SDSS DR5. This has increased the number of HeI* BAL quasars by more than one order of magnitude. We further detected HeI*{lambda}3189 in 50% (52/101) of the quasars in the sample. The detection fraction of HeI* BALs in MgII BAL quasars is ~35% as a whole, and it increases dramatically with increasing spectral signal-to-noise ratio (S/N), from ~18% at S/N<=10 to ~93% at S/N>=35. This suggests that HeI* BALs could be detected in most MgII LoBAL quasars, provided the spectra S/N is high enough. Such a surprisingly high HeI* BAL fraction is actually predicted from photoionization calculations based on a simple BAL model. The result indicates that HeI* absorption lines can be used to search for BAL quasars at low z, which cannot be identified by ground-based optical spectroscopic surveys with commonly seen UV absorption lines. Using HeI*{lambda}3889, we discovered 19 BAL quasars at z<0.3 from the available SDSS spectral database. The fraction of HeI* BAL quasars is similar to that of LoBAL objects.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/847/81
- Title:
- HeII photoionization rates of quasars
- Short Name:
- J/ApJ/847/81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The HeII transverse proximity effect-enhanced HeII Ly{alpha} transmission in a background sightline caused by the ionizing radiation of a foreground quasar-offers a unique opportunity to probe the morphology of quasar-driven HeII reionization. We conduct a comprehensive spectroscopic survey to find z~3 quasars in the foreground of 22 background quasar sightlines with Hubble Space Telescope/COS HeII Ly{alpha} transmission spectra. With our two-tiered survey strategy, consisting of a deep pencil-beam survey and a shallow wide-field survey, we discover 131 new quasars, which we complement with known SDSS/BOSS quasars in our fields. Using a restricted sample of 66 foreground quasars with inferred HeII photoionization rates greater than the expected UV background at these redshifts ({Gamma}_QSO_^HeII^>5x10^-16^s^-1^) we perform the first statistical analysis of the HeII transverse proximity effect. Our results show qualitative evidence for a large object-to-object variance: among the four foreground quasars with the highest {Gamma}_QSO_^HeII^ only one (previously known) quasar is associated with a significant HeII transmission spike. We perform a stacking analysis to average down these fluctuations, and detect an excess in the average HeII transmission near the foreground quasars at 3{sigma} significance. This statistical evidence for the transverse proximity effect is corroborated by a clear dependence of the signal strength on {Gamma}_QSO_^HeII^. Our detection places a purely geometrical lower limit on the quasar lifetime of t_Q_>25Myr. Improved modeling would additionally constrain quasar obscuration and the mean free path of HeII-ionizing photons.
- ID:
- ivo://CDS.VizieR/J/ApJS/236/30
- Title:
- Herschel-ATLAS (H-ATLAS) DR2
- Short Name:
- J/ApJS/236/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) is a survey of 660deg^2^ with the PACS and SPIRE cameras in five photometric bands: 100, 160, 250, 350, and 500{mu}m. This is the second of three papers describing the data release for the large fields at the south and north Galactic poles (NGP and SGP). In this paper we describe the catalogs of far-infrared and submillimeter sources for the NGP and SGP, which cover 177.1deg^2^ and 303.4deg^2^, respectively. The catalogs contain 118980 sources for the NGP field and 193527 sources for the SGP field detected at more than 4{sigma} significance in any of the 250, 350, or 500{mu}m bands. The source detection is based on the 250{mu}m map, and we present photometry in all five bands for each source, including aperture photometry for sources known to be extended. The rms positional accuracy for the faintest sources is about 2.4" in both RA and DEC. We present a statistical analysis of the catalogs and discuss the practical issues-completeness, reliability, flux boosting, accuracy of positions, accuracy of flux measurements-necessary to use the catalogs for astronomical projects.
- ID:
- ivo://CDS.VizieR/J/ApJ/759/139
- Title:
- Herschel + MIPS photometry of GOODS sources
- Short Name:
- J/ApJ/759/139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the effects of active galactic nuclei (AGNs) and star formation activity on the infrared (0.3-1000{mu}m) spectral energy distributions (SEDs) of luminous infrared galaxies from z=0.5 to 4.0. We have compiled a large sample of 151 galaxies selected at 24{mu}m (S_24_>~100{mu}Jy) in the GOODS-N and ECDFS fields for which we have deep Spitzer IRS spectroscopy, allowing us to decompose the mid-IR spectrum into contributions from star formation and AGN activity. A significant portion (~25%) of our sample is dominated by an AGN (>50% of the mid-IR luminosity) in the mid-IR. Based on the mid-IR classification, we divide our full sample into four sub-samples: z~1 star-forming (SF) sources, z~2 SF sources, AGNs with clear 9.7{mu}m silicate absorption, and AGNs with featureless mid-IR spectra. From our large spectroscopic sample and wealth of multi-wavelength data, including deep Herschel imaging at 100, 160, 250, 350, and 500{mu}m, we use 95 galaxies with complete spectral coverage to create a composite SED for each sub-sample. We then fit a two-temperature component modified blackbody to the SEDs. We find that the IR SEDs have similar cold dust temperatures, regardless of the mid-IR power source, but display a marked difference in the warmer dust temperatures. We calculate the average effective temperature of the dust in each sub-sample and find a significant (~20K) difference between the SF and AGN systems. We compare our composite SEDs to local templates and find that local templates do not accurately reproduce the mid-IR features and dust temperatures of our high-redshift systems. High-redshift IR luminous galaxies contain significantly more cool dust than their local counterparts. We find that a full suite of photometry spanning the IR peak is necessary to accurately account for the dominant dust temperature components in high-redshift IR luminous galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJS/222/16
- Title:
- Herschel obs. of major-merger pairs of z<0.1 galaxies
- Short Name:
- J/ApJS/222/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Herschel PACS and SPIRE far-infrared (FIR) and submillimeter imaging observations for a large K-band selected sample of 88 close major-merger pairs of galaxies (H-KPAIRs) in 6 photometric bands (70, 100, 160, 250, 350, and 500{mu}m). Among 132 spiral galaxies in the 44 spiral-spiral (S+S) pairs and 44 spiral-elliptical (S+E) pairs, 113 are detected in at least 1 Herschel band. The star formation rate (SFR) and dust mass (M_dust_) are derived from the IR SED fitting. The mass of total gas (M_gas_) is estimated by assuming a constant dust-to-gas mass ratio of 0.01. Star-forming spiral galaxies (SFGs) in S+S pairs show significant enhancements in both specific star formation rate (sSFR) and star formation efficiency (SFE), while having nearly the same gas mass compared to control galaxies. On the other hand, for SFGs in S+E pairs, there is no significant sSFR enhancement and the mean SFE enhancement is significantly lower than that of SFGs in S+S pairs. This suggests an important role for the disk-disk collision in the interaction-induced star formation. The M_gas_ of SFGs in S+E pairs is marginally lower than that of their counterparts in both S+S pairs and the control sample. Paired galaxies with and without interaction signs do not differ significantly in their mean sSFR and SFE. As found in previous works, this much larger sample confirms that the primary and secondary spirals in S+S pairs follow a Holmberg effect correlation on sSFR.
- ID:
- ivo://CDS.VizieR/J/A+A/572/A90
- Title:
- Herschel-VVDS-CFHTLS-D1 detections
- Short Name:
- J/A+A/572/A90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate of the properties of ~2000 Herschel/SPIRE far-infrared-selected galaxies from 0<z<4 in the CFHTLS-D1 field. Using a combination of extensive spectroscopy from the VVDS and ORELSE surveys, deep multiwavelength imaging from CFHT, VLA, Spitzer, XMM-Newton, and Herschel, and well-calibrated spectral energy distribution fitting, Herschel-bright galaxies are compared to optically-selected galaxies at a variety of redshifts. Herschel-selected galaxies are observed to span a range of stellar masses, colors, and absolute magnitudes equivalent to galaxies undetected in SPIRE. Though many Herschel galaxies appear to be in transition, such galaxies are largely consistent with normal star-forming galaxies when rest-frame colors are utilized. The nature of the star-forming "main sequence" is studied and we warn against adopting this framework unless the main sequence is determined precisely. Herschel galaxies at different total infrared luminosities (L_TIR_) are compared. Bluer optical colors, larger nebular extinctions, and larger contributions from younger stellar populations are observed for galaxies with larger L_TIR_, suggesting that low-L_TIR_ galaxies are undergoing rejuvenated starbursts while galaxies with higher L_TIR_ are forming a larger percentage of their stellar mass. A variety of methods are used to select powerful active galactic nuclei (AGN). Galaxies hosting all types of AGN are observed to be undergoing starbursts more commonly and vigorously than a matched sample of galaxies without powerful AGN and, additionally, the fraction of galaxies with an AGN increases with increasing SFR at all redshifts. At all redshifts (0<z<4) the most prodigious star-forming galaxies are found to contain the highest fraction of powerful AGN. For redshift bins that allow a comparison (z>0.5), the highest L_TIR_ galaxies in a given redshift bin are unobserved by SPIRE at subsequently lower redshifts, a trend linked to downsizing. In conjunction with other results, this evidence is used to argue for prevalent AGN-driven quenching in starburst galaxies across cosmic time.
- ID:
- ivo://CDS.VizieR/J/ApJ/736/31
- Title:
- HETDEX pilot survey. II. 1.9<z<3.8 LAEs
- Short Name:
- J/ApJ/736/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the escape of Ly{alpha} photons from Ly{alpha} emitting galaxies (LAEs) and the overall galaxy population using a sample of 99 LAEs at 1.9<z<3.8 detected through integral-field spectroscopy of blank fields by The Hobby Eberly Telescope Dark Energy Experiment Pilot Survey. For 89 LAEs with broadband counterparts we measure ultraviolet (UV) luminosities and UV slopes, and estimate E(B-V) under the assumption of a constant intrinsic UV slope for LAEs. These quantities are used to estimate dust-corrected star formation rates (SFRs). Comparison between the observed Ly{alpha} luminosity and that predicted by the dust-corrected SFR yields the Ly{alpha} escape fraction. We also measure the Ly{alpha} luminosity function and luminosity density ({rho}_Ly{alpha}_) at 2<z<4. Using this and other measurements from the literature at 0.3<z<7.7 we trace the redshift evolution of {rho}_Ly{alpha}_. We compare it to the expectations from the star formation history of the universe and characterize the evolution of the Ly{alpha} escape fraction of galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJS/245/3
- Title:
- HI 21cm and OH 18cm absorption search with the GBT
- Short Name:
- J/ApJS/245/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a large search for intrinsic HI 21cm and OH 18cm absorption in 145 compact radio sources in the redshift range 0.02<z<3.8 with the Green Bank Telescope. We redetect HI 21cm absorption toward six known absorption systems, but detect no new HI or OH absorption in 102 interference-free sources. Seventy-nine sources have not previously been observed for HI 21cm absorption. We recover a mean optical depth limit of {tau}_3{sigma}_<0.023 for all the nondetections in the survey. Our results do not support the high intrinsic absorption rates found by previous studies in compact radio sources at low redshift. Our results do, however, support the hypothesis proposed by Curran+ (2019MNRAS.484.1182C) that high ultraviolet (UV) luminosity active galactic nuclei do not show intrinsic HI 21cm absorption, confirming a threshold of L_UV_=10^23^W/Hz, above which our intrinsic absorption fraction is zero (54 sources). The exact nature of the UV luminosity effect on HI absorption systems remains ambiguous. We additionally find no statistical correlation between the 1.4GHz radio luminosity or the source size and the 21cm absorption detection rate. We attribute the lack of intrinsic absorption in our survey to the UV luminosity effect caused by an optical selection bias and a decreased column density sensitivity with increasing redshift due to lower radio continuum flux densities, high radio frequency interference, and higher telescope system temperatures at low frequencies.
- ID:
- ivo://CDS.VizieR/J/A+A/650/A76
- Title:
- HI content in Coma cluster substructure
- Short Name:
- J/A+A/650/A76
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Galaxy clusters are some of largest structures in the universe. These very dense environments tend to be home to higher numbers of evolved galaxies than found in lower-density environments. It is well known that dense environments can influence the evolution of galaxies through the removal of the neutral gas (HI) reservoirs that fuel star formation. It is unclear which environment has a stronger effect: the local environment (i.e. the substructure within the cluster), or the cluster itself. Using the new HI data from the Westerbork Coma Survey, we explore the average HI content of galaxies across the cluster comparing galaxies that reside in substructure to those that do not. We applied the Dressler-Shectman test to our newly compiled redshift catalogue of the Coma cluster to search for substructure. With so few of the Coma galaxies directly detected in HI, we used the HI stacking technique to probe the average HI content below what can be directly detected. Using the Dressler-Shectman test, we find 15 substructures within the footprint of the Westerbork Coma Survey. We compare the average HI content for galaxies within substructure to those not in substructure. Using the HI stacking technique, we find that those Coma galaxies not detected in HI are more than 10-50 times more HI deficient than expected, which supports the scenario of an extremely efficient and rapid quenching mechanism. By studying the galaxies that are not directly detected in HI, we also find Coma to be more HI deficient than previously thought.
- ID:
- ivo://CDS.VizieR/J/A+A/470/787
- Title:
- High energy peaked BL Lacs optical spectros.
- Short Name:
- J/A+A/470/787
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The multi-frequency sedentary survey is a flux-limited, statistically well-defined sample of highly X-ray dominated (i.e., with a very high X-ray to radio flux ratio) BL Lacertae objects, which includes 150 sources. In this paper, the third of the series, we report the results of a dedicated optical spectroscopy campaign that, together with results from other independent optical follow-up programs, led to the spectroscopic identification of all sources in the sample. We carried out a systematic spectroscopic campaign for the observation of all unidentified objects of the sample using the ESO 3.6m, the KPNO 4m, and the TNG optical telescopes.
