- ID:
- ivo://CDS.VizieR/J/ApJ/861/37
- Title:
- Luminous WISE-selected quasars in SDSS Stripe 82
- Short Name:
- J/ApJ/861/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopically complete sample of 147 infrared-color-selected active galactic nuclei (AGNs) down to a 22{mu}m flux limit of 20mJy over the ~270deg^2^ of the Sloan Digital Sky Survey Stripe 82 region. Most of these sources are in the QSO luminosity regime (Lbol>~10^12^L_{sun}_) and are found out to z~3. We classify the AGNs into three types, finding 57 blue, unobscured Type-1 (broad-lined) sources; 69 obscured, Type-2 (narrow-lined) sources; and 21 moderately reddened Type-1 sources (broad-lined and E(B-V)>0.25). We study a subset of this sample in X-rays and analyze their obscuration to find that our spectroscopic classifications are in broad agreement with low, moderate, and large amounts of absorption for Type-1, red Type-1, and Type-2 AGNs, respectively. We also investigate how their X-ray luminosities correlate with other known bolometric luminosity indicators such as [OIII] line luminosity (L[OIII]) and infrared luminosity (L6{mu}m). While the X-ray correlation with L[OIII] is consistent with previous findings, the most infrared-luminous sources appear to deviate from established relations such that they are either underluminous in X-rays or overluminous in the infrared. Finally, we examine the luminosity function evolution of our sample, and by AGN type, in combination with the complementary, infrared-selected, AGN sample of Lacy et al. (2013), spanning over two orders of magnitude in luminosity. We find that the two obscured populations evolve differently, with reddened Type-1 AGNs dominating the obscured AGN fraction (~30%) for L_5{mu}m_>10^45^erg/s, while the fraction of Type-2 AGNs with L_5{mu}m_<10^45^erg/s rises sharply from 40% to 80% of the overall AGN population.
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- ID:
- ivo://CDS.VizieR/J/A+A/600/A20
- Title:
- Lupus YSOs X-shooter spectroscopy
- Short Name:
- J/A+A/600/A20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The mass accretion rate, M_acc_, is a key quantity for the understanding of the physical processes governing the evolution of accretion discs around young low-mass (M_{star}_<=2.0M_{sun}_) stars and substellar objects (YSOs). We present here the results of a study of the stellar and accretion properties of the (almost) complete sample of class II and transitional YSOs in the Lupus I, II, III and IV clouds, based on spectroscopic data acquired with the VLT/X-shooter spectrograph. Our study combines the dataset from our previous work with new observations of 55 additional objects. We have investigated 92 YSO candidates in total, 11 of which have been definitely identified with giant stars unrelated to Lupus. The stellar and accretion properties of the 81 bona fide YSOs, which represent more than 90% of the whole class II and transition disc YSO population in the aforementioned Lupus clouds, have been homogeneously and self-consistently derived, allowing for an unbiased study of accretion and its relationship with stellar parameters. The accretion luminosity, L_acc_, increases with the stellar luminosity, L*, with an overall slope of ~1.6, similar but with a smaller scatter than in previous studies. There is a significant lack of strong accretors below L*~=0.1L_{sun}_, where L_acc_ is always lower than 0.01L*. We argue that the L_acc_-L* slope is not due to observational biases, but is a true property of the Lupus YSOs. The log M_acc_-logM* correlation shows a statistically significant evidence of a break, with a steeper relation for M*<=0.2M_{sun}_ and a flatter slope for higher masses. The bimodality of the M_acc_-M* relation is confirmed with four different evolutionary models used to derive the stellar mass. The bimodal behaviour of the observed relationship supports the importance of modelling self-gravity in the early evolution of the more massive discs, but other processes, such as photo-evaporation and planet formation during the YSO's lifetime, may also lead to disc dispersal on different timescales depending on the stellar mass. The sample studied here more than doubles the number of YSOs with homogeneously and simultaneously determined L_acc_ and luminosity, L_line_, of many permitted emission lines. Hence, we also refined the empirical relationships between L_acc_ and L_line_ on a more solid statistical basis.
- ID:
- ivo://CDS.VizieR/J/A+A/585/A145
- Title:
- LX Cyg optical, NIR and MIR spectra
- Short Name:
- J/A+A/585/A145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Mira variable LX Cygni (LX Cyg) showed a dramatic increase of its pulsation period in the recent decades and appears to undergo an important transition in its evolution. We aim at investigating the spectral type evolution of this star over the recent decades as well as during one pulsation cycle in more detail and discuss it in connection with the period evolution. We present optical, near- and mid-infrared low-resolution as well as optical high-resolution spectra to determine the current spectral type. The optical spectrum of LX Cyg has been followed for more than one pulsation cycle. Recent spectra are compared to archival spectra to trace the spectral type evolution and a Spitzer mid-IR spectrum is analysed for the presence of molecular and dust features. Furthermore, the current pulsation period is derived from AAVSO data. It is found that the spectral type of LX Cyg changed from S to C sometime between 1975 and 2008. Currently, the spectral type C is stable during a pulsation cycle. It is shown that spectral features typical of C-type stars are present in its spectrum from ~0.5 to 14{mu}m. An emission feature at 10.7{mu}m is attributed to SiC grains. The pulsation period of LX Cyg has increased from ~460d to ~580d within only 20 years, and is stable now. We conclude that the change in spectral type and the increase in pulsation period happened simultaneously and are causally connected. Both a recent thermal pulse (TP) and a simple surface temperature decrease appear unlikely to explain the observations. We therefore suggest that the underlying mechanism is related to a recent third dredge-up mixing event that brought up carbon from the interior of the star, i.e. that a genuine abundance change happened. We propose that LX Cyg is a rare transition type object that is uniquely suited to study the transformation from oxygen- to carbon-rich stars in detail.
- ID:
- ivo://CDS.VizieR/J/ApJ/888/89
- Title:
- Lya galaxies in 3 CFHTLS overdense regions
- Short Name:
- J/ApJ/888/89
- Date:
- 25 Oct 2021 10:16:31
- Publisher:
- CDS
- Description:
- We have carried out follow-up spectroscopy on three overdense regions of g- and r-dropout galaxies in the Canada-France-Hawaii Telescope Legacy Survey Deep Fields, finding two new protoclusters at z=4.898 and 3.721 and a possible protocluster at z=3.834. The z=3.721 protocluster overlaps with a previously identified protocluster at z=3.675. The redshift separation between these two protoclusters is {Delta}z=0.05, which is slightly larger than the size of typical protoclusters. Therefore, if they are not the progenitors of a >10^15^M_{sun}_ halo, they would grow into closely located independent halos like a supercluster. The other protocluster at z=4.898 is also surrounded by smaller galaxy groups. These systems including protoclusters and neighboring groups are regarded as the early phase of superclusters. We quantify the spatial distribution of member galaxies of the protoclusters at z=3.675 and 3.721 by fitting triaxial ellipsoids, finding a tentative difference: one has a pancake-like shape, while the other is filamentary. This could indicate that these two protoclusters are in different stages of formation. We investigate the relation between redshift and the velocity dispersion of protoclusters, including other protoclusters from the literature, in order to compare their dynamical states. Although there is no significant systematic trend in the velocity dispersions of protoclusters with redshift, the distribution is skewed to higher velocity dispersion over the redshift range of z=2-6. This could be interpreted as two phases of cluster formation, one dominated by the steady accretion of galaxies and the other by the merging between group-size halos, perhaps depending on the surrounding large-scale environments.
- ID:
- ivo://CDS.VizieR/J/ApJ/740/91
- Title:
- Ly{alpha} and OVI in galaxies around quasars
- Short Name:
- J/ApJ/740/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the association of galaxies with Ly{alpha} and OVI absorption, the most commonly detected transitions of the low-z intergalactic medium (IGM), in the fields of 14 quasars with z_em_=0.06-0.57. Confirming previous studies, we observe a high covering fraction for Ly{alpha} absorption to impact parameter {rho}=300h^-1^_72_kpc: 33/37 of our L>0.01L* galaxies show Ly{alpha} equivalent width W^Ly{alpha}^>=50 m{AA}. Galaxies of all luminosity L>0.01L* and spectral type are surrounded by a diffuse and ionized circumgalactic medium (CGM), whose baryonic mass is estimated at ~10^10.5^+/-0.3M_{sun}_ for a constant N_H_=10^19^cm^-2^. The virialized halos and extended CGM of present-day galaxies are responsible for most strong Ly{alpha} absorbers (W^Ly{alpha}^>300m{AA}) but cannot reproduce the majority of observed lines in the Ly{alpha} forest. We conclude that the majority of Ly{alpha} absorption with W^Ly{alpha}^=30-300m{AA} occurs in the cosmic web predicted by cosmological simulations and estimate a characteristic width for these filaments of ~400h^-1^_72_kpc. Regarding OVI, we observe a near unity covering fraction to {rho}=200h^-1^_72_kpc for L>0.1L* galaxies and to {rho}=300h^-1^_72_kpc for sub-L* (0.1 L*<L<L*) galaxies. Similar to our Ly{alpha} results, stronger OVI systems (W^1031^>70m{AA}) arise in the virialized halos of L>0.1L* galaxies. Unlike Ly{alpha}, the weaker OVI systems (W^1031^~30m{AA}) arise in the extended CGM of sub-L* galaxies. The majority of OVI gas observed in the low-z IGM is associated with a diffuse medium surrounding individual galaxies with L~0.3L* and rarely originates in the so-called warm-hot IGM (predicted by cosmological simulations.
- ID:
- ivo://CDS.VizieR/J/ApJ/859/53
- Title:
- Ly{alpha} candidates from a MUSE survey of 6 AGNs
- Short Name:
- J/ApJ/859/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent theoretical models suggest that the early phase of galaxy formation could involve an epoch when galaxies are gas rich but inefficient at forming stars: a "dark galaxy" phase. Here, we report the results of our Multi-Unit Spectroscopic Explorer (MUSE) survey for dark galaxies fluorescently illuminated by quasars at z>3. Compared to previous studies which are based on deep narrowband (NB) imaging, our integral field survey provides a nearly uniform sensitivity coverage over a large volume in redshift space around the quasars as well as full spectral information at each location. Thanks to these unique features, we are able to build control samples at large redshift distances from the quasars using the same data taken under the same conditions. By comparing the rest-frame equivalent width (EW0) distributions of the Ly{alpha} sources detected in proximity to the quasars and in control samples, we detect a clear correlation between the locations of high-EW0 objects and the quasars. This correlation is not seen in other properties, such as Ly{alpha} luminosities or volume overdensities, suggesting the possible fluorescent nature of at least some of these objects. Among these, we find six sources without continuum counterparts and EW0 limits larger than 240{AA} that are the best candidates for dark galaxies in our survey at z>3.5. The volume densities and properties, including inferred gas masses and star formation efficiencies, of these dark galaxy candidates are similar to those of previously detected candidates at z~2.4 in NB surveys. Moreover, if the most distant of these are fluorescently illuminated by the quasar, our results also provide a lower limit of t=60Myr on the quasar lifetime.
- ID:
- ivo://CDS.VizieR/J/A+AS/145/491
- Title:
- Ly{alpha} dipolar emission
- Short Name:
- J/A+AS/145/491
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Computer simulation techniques have been used to calculate the Stark broadening profiles of the hydrogen dipolar Lyman-{alpha} transition and of two-photon absorption, dispersion and polarization profiles in the 1S->2S transition. The calculations have considered electron densities in the range between 4.64*10^19^(m^-3^) and 1*10^23^(m^-3^), and temperatures in the range between 2000 and 100000K. The fine structure of level n=2 has been taken into account in the calculations. Four different sets of tables are given. The two first sets are the tables of the autocorrelation function for the dipolar moment of the emitter and for the operator that gives the transition amplitude for a two-photon absorption between the 1S and the 2S levels. This tables have the names rXXnYYYY.c1p and rXXnYYYY.c2p. The .c1p and .c2p extensions stands for 1 photon dipolar moment and for two-photon absorption transition amplitude. XX is 100*{rho}, {rho} being the quotient between the mean distance between particles and the Debye radius for the conditions of the plasma for which the profiles where calculated. YYYY is 100*Log(Ne), Ne being the electron density (m^-3^) of the plasma considered. The last two sets of tables correspond to the 1 photon Lyman-{alpha} profiles (rXXnYYYY.d1p) and to two-photon polarization profiles (rXXnYYYY.p2p). In each file the results obtained considering perturbers of different reduced masses ({mu}) are tabulated in different columns. The caption of each file contains the conditions of electron density and plasma temperature for which the calculation was made.
- ID:
- ivo://CDS.VizieR/J/ApJ/760/128
- Title:
- Ly{alpha} emission from 4<z<6 sources in COSMOS
- Short Name:
- J/ApJ/760/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate spectroscopically measured Ly{alpha} equivalent widths (EWs) and escape fractions of 244 sources of which 95 are Lyman break galaxies (LBGs) and 106 Lyman alpha emitters (LAEs) at z~4.2, z~4.8, and z~5.6 selected from intermediate and narrowband observations. The sources were selected from the Cosmic Evolution Survey and observed with the DEIMOS spectrograph. We find that the distribution of EWs shows no evolution with redshift for both the LBG selected sources and the intermediate/narrowband LAEs. We also find that the Ly{alpha} escape fraction of intermediate/narrowband LAEs is on average higher and has a larger variation than the escape fraction of LBG selected sources. The escape fraction does not show a dependence with redshift. Similar to what has been found for LAEs at low redshifts, the sources with the highest extinctions show the lowest escape fractions. The range of escape fractions increases with decreasing extinction. This is evidence that the dust extinction is the most important factor affecting the escape of Ly{alpha} photons, but at low extinctions other factors, such as the H I covering fraction and gas kinematics, can be just as effective at inhibiting the escape of Ly{alpha} photons.
- ID:
- ivo://CDS.VizieR/J/ApJ/903/4
- Title:
- 260 Ly{alpha} Emitters at Redshift z~5.7 with M2FS
- Short Name:
- J/ApJ/903/4
- Date:
- 15 Mar 2022
- Publisher:
- CDS
- Description:
- We present a spectroscopic survey of Ly{alpha} emitters (LAEs) at z~5.7 using the multiobject spectrograph M2FS on the Magellan Clay telescope. This is part of a high-redshift galaxy survey carried out in several well-studied deep fields. These fields have deep images in multiple UV/optical bands, including a narrow NB816 band that has allowed an efficient selection of LAE candidates at z~5.7. Our sample consists of 260 LAEs and covers a total effective area of more than 2deg^2^ on the sky. This is so far the largest (spectroscopically confirmed) sample of LAEs at this redshift. We use the secure redshifts and narrowband photometry to measure Ly{alpha} luminosities. We find that these LAEs span a Ly{alpha} luminosity range of ~2x10^42^-5x10^43^erg/s and include some of the most luminous galaxies known at z>=5.7 in terms of Ly{alpha} luminosity. Most of them have rest-frame equivalent widths between 20 and 300{AA}, and more luminous Ly{alpha} emission lines tend to have broader line widths. We detect a clear offset of ~20{AA} between the observed Ly{alpha} wavelength distribution and the NB816 filter transmission curve, which can be explained by the intergalactic medium absorption of continua blueward of Ly{alpha} in the high-redshift spectra. This sample is being used to study the Ly{alpha} luminosity function and galaxy properties at z~5.7.
- ID:
- ivo://CDS.VizieR/J/MNRAS/471/267
- Title:
- Ly{alpha} fluxes of HDFS 2.91<z<6.64 sources
- Short Name:
- J/MNRAS/471/267
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first estimate of the Ly{alpha} luminosity function using blind spectroscopy from the Multi Unit Spectroscopic Explorer, MUSE, in the Hubble Deep Field-South. Using automatic source-detection software, we assemble a homogeneously detected sample of 59 Ly{alpha} emitters covering a flux range of -18.0<log_10_(F)<-16.3(erg/s/cm2), corresponding to luminosities of 41.4<log_10_(L)<42.8(erg/s). As recent studies have shown, Ly{alpha} fluxes can be underestimated by a factor of 2 or more via traditional methods, and so we undertake a careful assessment of each object's Ly{alpha} flux using a curve-of-growth analysis to account for extended emission. We describe our self-consistent method for determining the completeness of the sample, and present an estimate of the global Ly {alpha} luminosity function between redshifts 2.91<z<6.64 using the 1/V_max_ estimator. We find that the luminosity function is higher than many number densities reported in the literature by a factor of 2-3, although our result is consistent at the 1{sigma} level with most of these studies. Our observed luminosity function is also in good agreement with predictions from semi-analytic models, and shows no evidence for strong evolution between the high- and low-redshift halves of the data. We demonstrate that one's approach to Ly{alpha} flux estimation does alter the observed luminosity function, and caution that accurate flux assessments will be crucial in measurements of the faint-end slope. This is a pilot study for the Ly{alpha} luminosity function in the MUSE deep-fields, to be built on with data from the Hubble Ultra Deep Field that will increase the size of our sample by almost a factor of 10.
