- ID:
- ivo://CDS.VizieR/J/A+A/457/79
- Title:
- VIMOS VLT Deep Survey: faint type-1 AGN sample
- Short Name:
- J/A+A/457/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the type-1 active galactic nuclei (AGN) sample extracted from the VIMOS VLT Deep Survey's first observations of 21000 spectra in 1.75{deg}^2^. This sample, which is purely magnitude-limited and free of morphological or color-selection biases, contains 130 broad-line AGN (BLAGN) spectra with redshift up to 5. Our data are divided into a wide (I_AB_<=22.5) and a deep (I_AB_<=24) subsample containing 56 and 74 objects, respectively. Because of its depth and selection criteria, this sample is uniquely suited for studying the population of faint type-1 AGN. Our measured surface density (~472+/-48 BLAGN per square degree with I_AB_<=24) is significantly higher than that of any other optically selected sample of BLAGN with spectroscopic confirmation. By applying a morphological and color analysis to our AGN sample, we find that (1) ~23% of the AGN brighter than I_AB_=22.5 are classified as extended, and this percentage increases to ~42 for those with z<1.6; (2) a non-negligible fraction of our BLAGN are lying close to the color-space area occupied by stars in the u*-g' versus g'-r' color-color diagram. This leads us to the conclusion that the classical optical-ultraviolet preselection technique, if employed at such deep magnitudes (I_AB_=22.5) in conjuction with a preselection of point-like sources, can miss up to ~35% of the AGN population. Finally, we present a composite spectrum of our sample of objects. While the continuum shape is very similar to that of the SDSS composite at short wavelengths, it is much redder than that of the SDSS composite at {lambda}>=3000{AA}. We interpret this as due to significant contamination from emission of the host galaxies, as expected from the faint absolute magnitudes sampled by our survey.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/559/A14
- Title:
- VIMOS VLT Deep Survey final data release
- Short Name:
- J/A+A/559/A14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Deep representative surveys of galaxies at different epochs are needed to make progress in understanding galaxy evolution. We describe the completed VIMOS VLT Deep Survey and the final data release of 35016 galaxies and type-I AGN with measured spectroscopic redshifts covering all epochs up to redshift z~6.7, in areas from 0.142 to 8.7 square degrees, and volumes from 0.5x10^6^ to 2x10^7^h^-3^*Mpc^3^. We selected samples of galaxies based solely on their i-band magnitude reaching i_AB_=24.75. Spectra were obtained with VIMOS on the ESO-VLT integrating 0.75h, 4.5h, and 18h for the Wide, Deep, and Ultra-Deep nested surveys, respectively. We demonstrate that any "redshift desert" can be crossed successfully using spectra covering 3650<={lambda}<=9350{AA}. A total of 1263 galaxies were again observed independently within the VVDS and from the VIPERS and MASSIV surveys. They were used to establish the redshift measurements reliability, to assess completeness in the VVDS sample, and to provide a weighting scheme taking the survey selection function into account. We describe the main properties of the VVDS samples, and the VVDS is compared to other spectroscopic surveys in the literature. In total we have obtained spectroscopic redshifts for 34594 galaxies, 422 type-I AGN, and 12430 Galactic stars. The survey enabled identifying galaxies up to very high redshifts with 4669 redshifts in 1<=z_spec_<=2, 561 in 2<=z_spec_<=3, and 468 with z_spec_>3, and specific populations like Lyman-{alpha} emitters were identified out to z=6.62. We show that the VVDS occupies a unique place in the parameter space defined by area, depth, redshift coverage, and number of spectra. The VIMOS VLT Deep Survey provides a comprehensive survey of the distant universe, covering all epochs since z~6, or more than 12Gyr of cosmic time, with a uniform selection, which is the largest such sample to date. A wealth of science results derived from the VVDS have shed new light on the evolution of galaxies and AGN and on their distribution in space over this large cosmic time. The VVDS further demonstrates that large deep spectroscopic redshift surveys over all these epochs in the distant Universe are a key tool to observational cosmology. To enhance the legacy value of the survey, a final public release of the complete VVDS spectroscopic redshift sample is available at http://cesam.lam.fr/vvds .
- ID:
- ivo://CDS.VizieR/J/ApJS/186/191
- Title:
- VI photometry and spectroscopy in h+{chi} Per
- Short Name:
- J/ApJS/186/191
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From photometric observations of ~47000 stars and spectroscopy of ~11000 stars, we describe the first extensive study of the stellar population of the famous Double Cluster, h and {chi} Persei, down to subsolar masses. By analyzing optical spectra and optical/infrared photometry, we constrain the distance moduli (dM), reddening (E(B-V)), and ages for h Persei, {chi} Persei, and the low-density halo population surrounding both cluster cores. With the exception of mass and spatial distribution, the clusters are nearly identical in every measurable way. From these data, we establish the first spectroscopic and photometric membership lists of cluster stars down to early/mid M dwarfs. At minimum, there are ~5000 members within 10' of the cluster centers, while the entire h and {chi} Persei region has at least ~13000 and as many as 20000 members. The Double Cluster contains ~8400M_{sun}_ of stars within 10' of the cluster centers. We estimate a total mass of at least 20000M_{sun}_. We conclude our study by outlining outstanding questions regarding the past and present properties of h and {chi} Persei. From comparing recent work, we compile a list of intrinsic colors and derive a new effective temperature scale for O-M dwarfs, giants, and supergiants.
- ID:
- ivo://CDS.VizieR/J/A+A/615/A96
- Title:
- VI photometry in 3 dwarf galaxies
- Short Name:
- J/A+A/615/A96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The abundance and spatial distribution of dwarf galaxies are excellent empirical benchmarks against which to test models of structure formation on small scales. The nearby Centaurus group, with its two subgroups centered on Cen A and M 83, stands out as an important alternative to the Local Group for scrutinizing cosmological model predictions in a group of galaxies context. We have obtained deep optical images of three recently discovered M 83 satellite galaxy candidates with the FORS2 instrument mounted on the Very Large Telescope. We aim to confirm their group membership and study their stellar population. Deep V I-band photometry was used to resolve the brightest stars in our targets. Artificial star tests are performed to estimate the completeness and uncertainties of the photometry. The color-magnitude diagrams reveal the red giant branch (RGB) stars, allowing us to use the Sobel edge detection method to measure the magnitude of the RGB tip and thus derive distances and group membership for our targets. The mean metallicity of the dwarf galaxies were further determined by fitting BASTI model isochrones to the mean RGB locus.
- ID:
- ivo://CDS.VizieR/J/AJ/128/224
- Title:
- VI photometry in M33 outer regions
- Short Name:
- J/AJ/128/224
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep CCD photometry in the VI passbands using the WIYN 3.5m telescope of a field located approximately 20 southeast of the center of M33; this field includes the region studied by Mould & Kristian in 1986ApJ...305..591M. The color-magnitude diagram (CMD) extends to I~25 and shows a prominent red giant branch (RGB), along with significant numbers of asymptotic giant branch and young main-sequence stars.
3446. VI photometry in NGC 188
- ID:
- ivo://CDS.VizieR/J/A+A/390/961
- Title:
- VI photometry in NGC 188
- Short Name:
- J/A+A/390/961
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used HST-WFPC2 to study the white dwarf luminosity function of the old open cluster NGC 188 in order to determine a lower limit to the age of the cluster (~5Gyr) by looking at the faint end of the cooling sequence (down to V~26.5).
- ID:
- ivo://CDS.VizieR/J/AJ/149/66
- Title:
- VI photometry of 8 Cepheid candidates in M31
- Short Name:
- J/AJ/149/66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ultra-long-period Cepheids (ULPCs) are classical Cepheids with pulsation periods exceeding ~80days. The intrinsic brightness of ULPCs are ~1 to ~3mag brighter than their shorter period counterparts. This makes them attractive in future distance scale work to derive distances beyond the limit set by the shorter period Cepheids. We have initiated a program to search for ULPCs in M31, using the single-band data taken from the Palomar Transient Factory, and identified eight possible candidates. In this work, we presented the VI-band follow-up observations of these eight candidates. Based on our VI-band light curves of these candidates and their locations in the color-magnitude diagram and the Period-Wesenheit diagram, we verify two candidates as being truly ULPCs. The six other candidates are most likely other kinds of long-period variables. With the two confirmed M31 ULPCs, we tested the applicability of ULPCs in distance scale work by deriving the distance modulus of M31. It was found to be {mu}_M31,ULPC_=24.30+/-0.76mag. The large error in the derived distance modulus, together with the large intrinsic dispersion of the Period-Wesenheit (PW) relation and the small number of ULPCs in a given host galaxy, means that the question of the suitability of ULPCs as standard candles is still open. Further work is needed to enlarge the sample of calibrating ULPCs and reduce the intrinsic dispersion of the PW relation before re-considering ULPCs as suitable distance indicators.
- ID:
- ivo://CDS.VizieR/J/A+A/581/A13
- Title:
- VI photometry of globular ESO 37-1
- Short Name:
- J/A+A/581/A13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the Milky Way, most globular clusters are highly conspicuous objects that were found centuries ago. However, a few dozen of them are faint, sparsely populated systems that were identified largely during the second half of the past century. One of the faintest is ESO 37-1 (E 3) and as such it remains poorly studied, with no spectroscopic observations published so far although it was discovered in 1976. We investigate the globular cluster E3 in an attempt to better constrain its fundamental parameters. Spectroscopy of stars in the field of E3 is shown here for the first time. Deep, precise VI CCD photometry of E3 down to V~26mag is presented and analysed. Low-resolution, medium signal-to-noise ratio spectra of nine candidate members are studied to derive radial velocity and metallicity. Proper motions from the UCAC4 catalogue are used to explore the kinematics of the bright members of E3. Isochrone fitting indicates that E3 is probably very old, with an age of about 13Gyr; its distance from the Sun is nearly 10kpc. It is also somewhat metal rich with [Fe/H]=-0.7. Regarding its kinematics, our tentative estimate for the proper motions is ({mu}_{alpha}*cos{delta}, {mu}_{delta}_=(-7.0+/-0.8, 3.5+/-0.3)mas/yr (or a tangential velocity of 382+/-79km/s) and for the radial velocity 45+/-5km/s in the solar rest frame. E3 is one of the most intriguing globular clusters in the Galaxy. Having an old age and being metal rich is clearly a peculiar combination, only seen in a handful of objects like the far more conspicuous NGC 104 (47 Tucanae). In addition, its low luminosity and sparse population make it a unique template for the study of the final evolutionary phases in the life of a star cluster. Unfortunately, E3 is among the most elusive and challenging known globular clusters because field contamination severely hampers spectroscopic studies.
- ID:
- ivo://CDS.VizieR/J/A+A/366/498
- Title:
- VI photometry of M33 star clusters
- Short Name:
- J/A+A/366/498
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have detected 102 star clusters in M 33, from 35 deep Hubble Space Telescope (HST) WFPC2 fields taken from our program and from the HST archive. Twenty-eight fields have V and I band imaging, and an additional seven fields are imaged in a single V filter. Eighty-two of the clusters were previously unknown. Integrated photometry reveals that 25 clusters have (V-I) colors typical of those found in Galactic globular clusters (only ten of these objects were previously known). Our discovery of 15 new globular cluster candidates increases previous estimates of the old cluster population in M 33 by ~60%. An additional eleven objects (only two were previously known) have colors expected for intermediate age clusters. The new clusters have a range of ages from 6 million years to >15Gyrs, and masses between 10^2^M_{sun}_-10^6^M_{sun}_, although these parameters are estimated from only one color.
- ID:
- ivo://CDS.VizieR/J/A+A/507/803
- Title:
- VI photometry of new M53 variables
- Short Name:
- J/A+A/507/803
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the variable star content of the globular cluster M53 to compute the physical parameters of the constituting stars and the distance of the cluster. Covering two adjacent seasons in 2007 and 2008, new photometric data are gathered for 3048 objects in the field of M53. By using the OIS (optimal image subtraction) method and subsequently TFA (trend filtering algorithm), we search for variables in the full sample by using discrete Fourier transformation and box-fitting least squares method. We select variables based on the statistics related to these methods combined with visual inspection. We identified 12 new variables (2 RR Lyrae stars, 7 short periodic stars - 3 of them are SX Phe stars - and 3 long-period variables). No eclipsing binaries were found in the present sample. Except for the 3 (hitherto unknown) Blazhko RR Lyrae (two RRab and an RRc) stars, no multiperiodic variables were found. We showed that after proper period shift, the PLC (period-luminosity-color) relation for the first overtone RR Lyrae sample tightly follows the one spanned by the fundamental stars. Furthermore, the slope is in agreement with that derived from other clusters. Based on the earlier Baade-Wesselink calibration of the PLC relations, the derived reddening-free distance modulus of M53 is 16.31+/-0.04mag, corresponding to a distance modulus of 18.5mag for the Large Magellanic Cloud. From the Fourier parameters of the RRab stars we obtained an average iron abundance of -1.58+/-0.03 (error of the mean). This is ~0.5dex higher than the overall abundance of the giants as given in the literature and derived in this paper from the three-color photometry of giants. We suspect that the source of this discrepancy (observable also in other, low-metallicity clusters) is the lack of a sufficient number of low-metallicity objects in the calibrating sample of the Fourier method.
