Exploration of quasars with theGaiamission

Abstract

We analyze the opportunities in and limits to investigating quasars with the Gaia satellite by studying Gaia's low-and high-resolution quasar spectra, with consideration of their signal-to-noise ratios. Furthermore, we explore bright quasars from the Sloan Digital Sky Survey with broad emission lines (BELs) redshifted into the spectral range of Gaia's Radial Velocity Spectrograph (RVS). We find that Gaia low-resolution spectra of quasars enable a determination of equivalent widths, continuum variability, and the Baldwin effect. Additionally, it will be feasible to analyze BEL reverberation mapping with Gaia data for a small sample of objects. These quasars should have a high cadence of measurements or higher time lags due to large redshifts, high quasar luminosities, or selected lowionization lines. More than 500 known quasars will also get high-resolution spectra of individual BELs in the small wavelength range of the RVS. This allows an investigation of broad emission line shapes and their variabilities to get information on the spatial structure and kinematics of the broad line region. We identify six known variable SDSS quasars with BELs in the RVS that have interesting spectra for a potential intrinsic line variability investigation. However, the signal-to-noise ratio of the RVS is too small for studying narrow and broad absorption lines in quasar spectra.

Globular clusters with Gaia

“…Gaia will observe not only stars, but also tens of thousands of quasars, unresolved galaxies, Solar system objects, many transient and variable objects like supernovae, and finally the interstellar medium (Altavilla et al 2012;Ducourant et al 2014;Eyer et al 2014;de Bruijne et al 2015;Proft & Wambsganss 2015;Zwitter & Kos 2015;Bachchan, Hobbs, & Lindegren 2016;Tanga et al 2016). Gaia will also pose a challenge because of its data amount and complexity, pushing the astrophysical community farther into the path of big data and data mining (Gaia Collaboration 2016a).…”

Gaia Space Mission and Quasars

“…Vertical stripe at ∼8,600 Å is the wavelength range of Gaia's spectroscopic instrument. In our view the figure, which summarizes simulations of Proft et al (2015), clearly demonstrates the ability of Gaia to determine photometric redshifts for a complete population of quasars down to V ∼20. For brighter objects even changes in their spectral energy distribution (SED) should be detectable.…”

“…For brighter objects even changes in their spectral energy distribution (SED) should be detectable. Proft et al (2015) demonstrate that variability of SDSS 154757.71+060626.6, which has Sloan red magnitude r ′ = 17.5 and redshift z = 2.03, is clearly within the reach of Gaia.…”

“…Magnitude and wavelength limitations of Gaia's spectroscopic instrument are being complemented by ground-based optical stellar spectroscopic surveys which are aimed to obtain stellar parameters and accurate radial velocities, as well as abundances of individual elements for FIGURE 1 | Positional error after a 5-year mission as a function of V magnitude. The latter was derived from Gaia's intrinsic G magnitude using the relation V = 1.02 G − 0.24, which is appropriate for quasars with z ≤ 4 (Proft et al, 2015). Positional error estimate assumes a point-like source and follows Equations (4-7) from Prusti et al (2016) with 0.54 < V − I < 0.98. stars which are not within the reach of Gaia.…”

Galaxies as High-resolution Telescopes

“…The combination of offsets measured using Gaia and gravitational lensing will give us a complementary insight into inner regions of galaxies at all redshifts. It is also expected that Gaia can detect more than 500 000 quasars (Proft & Wambsganss 2015), and among them about 3000 gravitationally lensed quasars (Finet et al 2012). Gaia astrometry for these gravitationally lensed quasars will provide an excellent frame for comparison of mirage image positions.…”